Re: [PATCH v3 7/8] arm64: mm: Set ZONE_DMA size based on early IORT scan
On 2020/10/16 15:27, Hanjun Guo wrote:
The patch only takes the address limit field into account if its value
> 0.
Sorry I missed the if (*->memory_address_limit) check, thanks
for the reminding.
Also, before commit 7fb89e1d44cb6aec ("ACPI/IORT: take _DMA methods
into account for named components"), the _DMA method was not taken
into account for named components at all, and only the IORT limit was
used, so I do not anticipate any problems with that.
Then this patch is fine to me.
Certainly we need to address Lorenzo's comments.
Thanks
Hanjun
___
iommu mailing list
iommu@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/iommu
Re: [PATCH v3 7/8] arm64: mm: Set ZONE_DMA size based on early IORT scan
Hi Ard,
On 2020/10/16 14:54, Ard Biesheuvel wrote:
On Fri, 16 Oct 2020 at 08:51, Hanjun Guo wrote:
On 2020/10/16 2:03, Catalin Marinas wrote:
On Thu, Oct 15, 2020 at 10:26:18PM +0800, Hanjun Guo wrote:
On 2020/10/15 3:12, Nicolas Saenz Julienne wrote:
From: Ard Biesheuvel
We recently introduced a 1 GB sized ZONE_DMA to cater for platforms
incorporating masters that can address less than 32 bits of DMA, in
particular the Raspberry Pi 4, which has 4 or 8 GB of DRAM, but has
peripherals that can only address up to 1 GB (and its PCIe host
bridge can only access the bottom 3 GB)
Instructing the DMA layer about these limitations is straight-forward,
even though we had to fix some issues regarding memory limits set in
the IORT for named components, and regarding the handling of ACPI _DMA
methods. However, the DMA layer also needs to be able to allocate
memory that is guaranteed to meet those DMA constraints, for bounce
buffering as well as allocating the backing for consistent mappings.
This is why the 1 GB ZONE_DMA was introduced recently. Unfortunately,
it turns out the having a 1 GB ZONE_DMA as well as a ZONE_DMA32 causes
problems with kdump, and potentially in other places where allocations
cannot cross zone boundaries. Therefore, we should avoid having two
separate DMA zones when possible.
So let's do an early scan of the IORT, and only create the ZONE_DMA
if we encounter any devices that need it. This puts the burden on
the firmware to describe such limitations in the IORT, which may be
redundant (and less precise) if _DMA methods are also being provided.
However, it should be noted that this situation is highly unusual for
arm64 ACPI machines. Also, the DMA subsystem still gives precedence to
the _DMA method if implemented, and so we will not lose the ability to
perform streaming DMA outside the ZONE_DMA if the _DMA method permits
it.
Sorry, I'm still a little bit confused. With this patch, if we have
a device which set the right _DMA method (DMA size >= 32), but with the
wrong DMA size in IORT, we still have the ZONE_DMA created which
is actually not needed?
With the current kernel, we get a ZONE_DMA already with an arbitrary
size of 1GB that matches what RPi4 needs. We are trying to eliminate
such unnecessary ZONE_DMA based on some heuristics (well, something that
looks "better" than a OEM ID based quirk). Now, if we learn that IORT
for platforms in the field is that broken as to describe few bits-wide
DMA masks, we may have to go back to the OEM ID quirk.
Some platforms using 0 as the memory size limit, for example D05 [0] and
D06 [1], I think we need to go back to the OEM ID quirk.
For D05/D06, there are multi interrupt controllers named as mbigen,
mbigen is using the named component to describe the mappings with
the ITS controller, and mbigen is using 0 as the memory size limit.
Also since the memory size limit for PCI RC was introduced by later
IORT revision, so firmware people may think it's fine to set that
as 0 because the system works without it.
Hello Hanjun,
The patch only takes the address limit field into account if its value > 0.
Sorry I missed the if (*->memory_address_limit) check, thanks
for the reminding.
Also, before commit 7fb89e1d44cb6aec ("ACPI/IORT: take _DMA methods
into account for named components"), the _DMA method was not taken
into account for named components at all, and only the IORT limit was
used, so I do not anticipate any problems with that.
Then this patch is fine to me.
Thanks
Hanjun
___
iommu mailing list
iommu@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/iommu
Re: [PATCH v3 7/8] arm64: mm: Set ZONE_DMA size based on early IORT scan
On Thu, 15 Oct 2020 at 12:31, Lorenzo Pieralisi
wrote:
>
> On Wed, Oct 14, 2020 at 09:12:09PM +0200, Nicolas Saenz Julienne wrote:
>
> [...]
>
> > +unsigned int __init acpi_iort_get_zone_dma_size(void)
> > +{
> > + struct acpi_table_iort *iort;
> > + struct acpi_iort_node *node, *end;
> > + acpi_status status;
> > + u8 limit = 32;
> > + int i;
> > +
> > + if (acpi_disabled)
> > + return limit;
> > +
> > + status = acpi_get_table(ACPI_SIG_IORT, 0,
> > + (struct acpi_table_header **));
> > + if (ACPI_FAILURE(status))
> > + return limit;
> > +
> > + node = ACPI_ADD_PTR(struct acpi_iort_node, iort, iort->node_offset);
> > + end = ACPI_ADD_PTR(struct acpi_iort_node, iort, iort->header.length);
> > +
> > + for (i = 0; i < iort->node_count; i++) {
> > + if (node >= end)
> > + break;
> > +
> > + switch (node->type) {
> > + struct acpi_iort_named_component *ncomp;
> > + struct acpi_iort_root_complex *rc;
> > +
> > + case ACPI_IORT_NODE_NAMED_COMPONENT:
> > + ncomp = (struct acpi_iort_named_component
> > *)node->node_data;
> > + if (ncomp->memory_address_limit)
> > + limit = min(limit,
> > ncomp->memory_address_limit);
> > + break;
> > +
> > + case ACPI_IORT_NODE_PCI_ROOT_COMPLEX:
> > + rc = (struct acpi_iort_root_complex *)node->node_data;
> > + if (rc->memory_address_limit)
>
> You need to add a node revision check here, see rc_dma_get_range() in
> drivers/acpi/arm64/iort.c, otherwise we may be reading junk data
> in older IORT tables - acpica structures are always referring to the
> latest specs.
>
Indeed - apologies for not mentioning that when handing over the patch.
Also, we could use min_not_zero() here instead of the if ()
___
iommu mailing list
iommu@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/iommu
Re: [PATCH v3 7/8] arm64: mm: Set ZONE_DMA size based on early IORT scan
On Fri, 16 Oct 2020 at 08:51, Hanjun Guo wrote:
>
> On 2020/10/16 2:03, Catalin Marinas wrote:
> > On Thu, Oct 15, 2020 at 10:26:18PM +0800, Hanjun Guo wrote:
> >> On 2020/10/15 3:12, Nicolas Saenz Julienne wrote:
> >>> From: Ard Biesheuvel
> >>>
> >>> We recently introduced a 1 GB sized ZONE_DMA to cater for platforms
> >>> incorporating masters that can address less than 32 bits of DMA, in
> >>> particular the Raspberry Pi 4, which has 4 or 8 GB of DRAM, but has
> >>> peripherals that can only address up to 1 GB (and its PCIe host
> >>> bridge can only access the bottom 3 GB)
> >>>
> >>> Instructing the DMA layer about these limitations is straight-forward,
> >>> even though we had to fix some issues regarding memory limits set in
> >>> the IORT for named components, and regarding the handling of ACPI _DMA
> >>> methods. However, the DMA layer also needs to be able to allocate
> >>> memory that is guaranteed to meet those DMA constraints, for bounce
> >>> buffering as well as allocating the backing for consistent mappings.
> >>>
> >>> This is why the 1 GB ZONE_DMA was introduced recently. Unfortunately,
> >>> it turns out the having a 1 GB ZONE_DMA as well as a ZONE_DMA32 causes
> >>> problems with kdump, and potentially in other places where allocations
> >>> cannot cross zone boundaries. Therefore, we should avoid having two
> >>> separate DMA zones when possible.
> >>>
> >>> So let's do an early scan of the IORT, and only create the ZONE_DMA
> >>> if we encounter any devices that need it. This puts the burden on
> >>> the firmware to describe such limitations in the IORT, which may be
> >>> redundant (and less precise) if _DMA methods are also being provided.
> >>> However, it should be noted that this situation is highly unusual for
> >>> arm64 ACPI machines. Also, the DMA subsystem still gives precedence to
> >>> the _DMA method if implemented, and so we will not lose the ability to
> >>> perform streaming DMA outside the ZONE_DMA if the _DMA method permits
> >>> it.
> >>
> >> Sorry, I'm still a little bit confused. With this patch, if we have
> >> a device which set the right _DMA method (DMA size >= 32), but with the
> >> wrong DMA size in IORT, we still have the ZONE_DMA created which
> >> is actually not needed?
> >
> > With the current kernel, we get a ZONE_DMA already with an arbitrary
> > size of 1GB that matches what RPi4 needs. We are trying to eliminate
> > such unnecessary ZONE_DMA based on some heuristics (well, something that
> > looks "better" than a OEM ID based quirk). Now, if we learn that IORT
> > for platforms in the field is that broken as to describe few bits-wide
> > DMA masks, we may have to go back to the OEM ID quirk.
>
> Some platforms using 0 as the memory size limit, for example D05 [0] and
> D06 [1], I think we need to go back to the OEM ID quirk.
>
> For D05/D06, there are multi interrupt controllers named as mbigen,
> mbigen is using the named component to describe the mappings with
> the ITS controller, and mbigen is using 0 as the memory size limit.
>
> Also since the memory size limit for PCI RC was introduced by later
> IORT revision, so firmware people may think it's fine to set that
> as 0 because the system works without it.
>
Hello Hanjun,
The patch only takes the address limit field into account if its value > 0.
Also, before commit 7fb89e1d44cb6aec ("ACPI/IORT: take _DMA methods
into account for named components"), the _DMA method was not taken
into account for named components at all, and only the IORT limit was
used, so I do not anticipate any problems with that.
___
iommu mailing list
iommu@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/iommu
Re: [PATCH v3 7/8] arm64: mm: Set ZONE_DMA size based on early IORT scan
On 2020/10/16 2:03, Catalin Marinas wrote: On Thu, Oct 15, 2020 at 10:26:18PM +0800, Hanjun Guo wrote: On 2020/10/15 3:12, Nicolas Saenz Julienne wrote: From: Ard Biesheuvel We recently introduced a 1 GB sized ZONE_DMA to cater for platforms incorporating masters that can address less than 32 bits of DMA, in particular the Raspberry Pi 4, which has 4 or 8 GB of DRAM, but has peripherals that can only address up to 1 GB (and its PCIe host bridge can only access the bottom 3 GB) Instructing the DMA layer about these limitations is straight-forward, even though we had to fix some issues regarding memory limits set in the IORT for named components, and regarding the handling of ACPI _DMA methods. However, the DMA layer also needs to be able to allocate memory that is guaranteed to meet those DMA constraints, for bounce buffering as well as allocating the backing for consistent mappings. This is why the 1 GB ZONE_DMA was introduced recently. Unfortunately, it turns out the having a 1 GB ZONE_DMA as well as a ZONE_DMA32 causes problems with kdump, and potentially in other places where allocations cannot cross zone boundaries. Therefore, we should avoid having two separate DMA zones when possible. So let's do an early scan of the IORT, and only create the ZONE_DMA if we encounter any devices that need it. This puts the burden on the firmware to describe such limitations in the IORT, which may be redundant (and less precise) if _DMA methods are also being provided. However, it should be noted that this situation is highly unusual for arm64 ACPI machines. Also, the DMA subsystem still gives precedence to the _DMA method if implemented, and so we will not lose the ability to perform streaming DMA outside the ZONE_DMA if the _DMA method permits it. Sorry, I'm still a little bit confused. With this patch, if we have a device which set the right _DMA method (DMA size >= 32), but with the wrong DMA size in IORT, we still have the ZONE_DMA created which is actually not needed? With the current kernel, we get a ZONE_DMA already with an arbitrary size of 1GB that matches what RPi4 needs. We are trying to eliminate such unnecessary ZONE_DMA based on some heuristics (well, something that looks "better" than a OEM ID based quirk). Now, if we learn that IORT for platforms in the field is that broken as to describe few bits-wide DMA masks, we may have to go back to the OEM ID quirk. Some platforms using 0 as the memory size limit, for example D05 [0] and D06 [1], I think we need to go back to the OEM ID quirk. For D05/D06, there are multi interrupt controllers named as mbigen, mbigen is using the named component to describe the mappings with the ITS controller, and mbigen is using 0 as the memory size limit. Also since the memory size limit for PCI RC was introduced by later IORT revision, so firmware people may think it's fine to set that as 0 because the system works without it. Thanks Hanjun [0]: https://github.com/tianocore/edk2-platforms/blob/master/Silicon/Hisilicon/Hi1616/D05AcpiTables/D05Iort.asl [1]: https://github.com/tianocore/edk2-platforms/blob/master/Silicon/Hisilicon/Hi1620/Hi1620AcpiTables/Hi1620Iort.asl ___ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu
Re: [PATCH v3 7/8] arm64: mm: Set ZONE_DMA size based on early IORT scan
On Thu, Oct 15, 2020 at 10:26:18PM +0800, Hanjun Guo wrote: > On 2020/10/15 3:12, Nicolas Saenz Julienne wrote: > > From: Ard Biesheuvel > > > > We recently introduced a 1 GB sized ZONE_DMA to cater for platforms > > incorporating masters that can address less than 32 bits of DMA, in > > particular the Raspberry Pi 4, which has 4 or 8 GB of DRAM, but has > > peripherals that can only address up to 1 GB (and its PCIe host > > bridge can only access the bottom 3 GB) > > > > Instructing the DMA layer about these limitations is straight-forward, > > even though we had to fix some issues regarding memory limits set in > > the IORT for named components, and regarding the handling of ACPI _DMA > > methods. However, the DMA layer also needs to be able to allocate > > memory that is guaranteed to meet those DMA constraints, for bounce > > buffering as well as allocating the backing for consistent mappings. > > > > This is why the 1 GB ZONE_DMA was introduced recently. Unfortunately, > > it turns out the having a 1 GB ZONE_DMA as well as a ZONE_DMA32 causes > > problems with kdump, and potentially in other places where allocations > > cannot cross zone boundaries. Therefore, we should avoid having two > > separate DMA zones when possible. > > > > So let's do an early scan of the IORT, and only create the ZONE_DMA > > if we encounter any devices that need it. This puts the burden on > > the firmware to describe such limitations in the IORT, which may be > > redundant (and less precise) if _DMA methods are also being provided. > > However, it should be noted that this situation is highly unusual for > > arm64 ACPI machines. Also, the DMA subsystem still gives precedence to > > the _DMA method if implemented, and so we will not lose the ability to > > perform streaming DMA outside the ZONE_DMA if the _DMA method permits > > it. > > Sorry, I'm still a little bit confused. With this patch, if we have > a device which set the right _DMA method (DMA size >= 32), but with the > wrong DMA size in IORT, we still have the ZONE_DMA created which > is actually not needed? With the current kernel, we get a ZONE_DMA already with an arbitrary size of 1GB that matches what RPi4 needs. We are trying to eliminate such unnecessary ZONE_DMA based on some heuristics (well, something that looks "better" than a OEM ID based quirk). Now, if we learn that IORT for platforms in the field is that broken as to describe few bits-wide DMA masks, we may have to go back to the OEM ID quirk. -- Catalin ___ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu
Re: [PATCH v3 7/8] arm64: mm: Set ZONE_DMA size based on early IORT scan
On Thu, 2020-10-15 at 22:26 +0800, Hanjun Guo wrote: > On 2020/10/15 3:12, Nicolas Saenz Julienne wrote: > > From: Ard Biesheuvel > > > > We recently introduced a 1 GB sized ZONE_DMA to cater for platforms > > incorporating masters that can address less than 32 bits of DMA, in > > particular the Raspberry Pi 4, which has 4 or 8 GB of DRAM, but has > > peripherals that can only address up to 1 GB (and its PCIe host > > bridge can only access the bottom 3 GB) > > > > Instructing the DMA layer about these limitations is straight-forward, > > even though we had to fix some issues regarding memory limits set in > > the IORT for named components, and regarding the handling of ACPI _DMA > > methods. However, the DMA layer also needs to be able to allocate > > memory that is guaranteed to meet those DMA constraints, for bounce > > buffering as well as allocating the backing for consistent mappings. > > > > This is why the 1 GB ZONE_DMA was introduced recently. Unfortunately, > > it turns out the having a 1 GB ZONE_DMA as well as a ZONE_DMA32 causes > > problems with kdump, and potentially in other places where allocations > > cannot cross zone boundaries. Therefore, we should avoid having two > > separate DMA zones when possible. > > > > So let's do an early scan of the IORT, and only create the ZONE_DMA > > if we encounter any devices that need it. This puts the burden on > > the firmware to describe such limitations in the IORT, which may be > > redundant (and less precise) if _DMA methods are also being provided. > > However, it should be noted that this situation is highly unusual for > > arm64 ACPI machines. Also, the DMA subsystem still gives precedence to > > the _DMA method if implemented, and so we will not lose the ability to > > perform streaming DMA outside the ZONE_DMA if the _DMA method permits > > it. > > Sorry, I'm still a little bit confused. With this patch, if we have > a device which set the right _DMA method (DMA size >= 32), but with the > wrong DMA size in IORT, we still have the ZONE_DMA created which > is actually not needed? Yes, that would be the case. Regards, Nicolas signature.asc Description: This is a digitally signed message part ___ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu
Re: [PATCH v3 7/8] arm64: mm: Set ZONE_DMA size based on early IORT scan
On 2020/10/15 3:12, Nicolas Saenz Julienne wrote:
From: Ard Biesheuvel
We recently introduced a 1 GB sized ZONE_DMA to cater for platforms
incorporating masters that can address less than 32 bits of DMA, in
particular the Raspberry Pi 4, which has 4 or 8 GB of DRAM, but has
peripherals that can only address up to 1 GB (and its PCIe host
bridge can only access the bottom 3 GB)
Instructing the DMA layer about these limitations is straight-forward,
even though we had to fix some issues regarding memory limits set in
the IORT for named components, and regarding the handling of ACPI _DMA
methods. However, the DMA layer also needs to be able to allocate
memory that is guaranteed to meet those DMA constraints, for bounce
buffering as well as allocating the backing for consistent mappings.
This is why the 1 GB ZONE_DMA was introduced recently. Unfortunately,
it turns out the having a 1 GB ZONE_DMA as well as a ZONE_DMA32 causes
problems with kdump, and potentially in other places where allocations
cannot cross zone boundaries. Therefore, we should avoid having two
separate DMA zones when possible.
So let's do an early scan of the IORT, and only create the ZONE_DMA
if we encounter any devices that need it. This puts the burden on
the firmware to describe such limitations in the IORT, which may be
redundant (and less precise) if _DMA methods are also being provided.
However, it should be noted that this situation is highly unusual for
arm64 ACPI machines. Also, the DMA subsystem still gives precedence to
the _DMA method if implemented, and so we will not lose the ability to
perform streaming DMA outside the ZONE_DMA if the _DMA method permits
it.
Sorry, I'm still a little bit confused. With this patch, if we have
a device which set the right _DMA method (DMA size >= 32), but with the
wrong DMA size in IORT, we still have the ZONE_DMA created which
is actually not needed?
Cc: Jeremy Linton
Cc: Lorenzo Pieralisi
Cc: Nicolas Saenz Julienne
Cc: Rob Herring
Cc: Christoph Hellwig
Cc: Robin Murphy
Cc: Hanjun Guo
Cc: Sudeep Holla
Cc: Anshuman Khandual
Signed-off-by: Ard Biesheuvel
[nsaenz: Rebased, removed documentation change, warnings and add
declaration in acpi_iort.h]
Signed-off-by: Nicolas Saenz Julienne
---
arch/arm64/mm/init.c | 6 +
drivers/acpi/arm64/iort.c | 51 +++
include/linux/acpi_iort.h | 4 +++
3 files changed, 61 insertions(+)
diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
index 97b0d2768349..f321761eedb2 100644
--- a/arch/arm64/mm/init.c
+++ b/arch/arm64/mm/init.c
@@ -29,6 +29,7 @@
#include
#include
#include
+#include
#include
#include
@@ -196,6 +197,11 @@ static void __init zone_sizes_init(unsigned long min,
unsigned long max)
#ifdef CONFIG_ZONE_DMA
zone_dma_bits = min(zone_dma_bits,
(unsigned
int)ilog2(of_dma_get_max_cpu_address(NULL)));
+
+ if (IS_ENABLED(CONFIG_ACPI))
+ zone_dma_bits = min(zone_dma_bits,
+ acpi_iort_get_zone_dma_size());
+
arm64_dma_phys_limit = max_zone_phys(zone_dma_bits);
max_zone_pfns[ZONE_DMA] = PFN_DOWN(arm64_dma_phys_limit);
#endif
diff --git a/drivers/acpi/arm64/iort.c b/drivers/acpi/arm64/iort.c
index 9929ff50c0c0..8f530bf3c03b 100644
--- a/drivers/acpi/arm64/iort.c
+++ b/drivers/acpi/arm64/iort.c
@@ -1718,3 +1718,54 @@ void __init acpi_iort_init(void)
iort_init_platform_devices();
}
+
+#ifdef CONFIG_ZONE_DMA
+/*
+ * Check the IORT whether any devices exist whose DMA mask is < 32 bits.
+ * If so, return the smallest value encountered, or 32 otherwise.
+ */
+unsigned int __init acpi_iort_get_zone_dma_size(void)
+{
+ struct acpi_table_iort *iort;
+ struct acpi_iort_node *node, *end;
+ acpi_status status;
+ u8 limit = 32;
+ int i;
+
+ if (acpi_disabled)
+ return limit;
+
+ status = acpi_get_table(ACPI_SIG_IORT, 0,
+ (struct acpi_table_header **));
+ if (ACPI_FAILURE(status))
+ return limit;
+
+ node = ACPI_ADD_PTR(struct acpi_iort_node, iort, iort->node_offset);
+ end = ACPI_ADD_PTR(struct acpi_iort_node, iort, iort->header.length);
+
+ for (i = 0; i < iort->node_count; i++) {
+ if (node >= end)
+ break;
+
+ switch (node->type) {
+ struct acpi_iort_named_component *ncomp;
+ struct acpi_iort_root_complex *rc;
+
+ case ACPI_IORT_NODE_NAMED_COMPONENT:
+ ncomp = (struct acpi_iort_named_component
*)node->node_data;
+ if (ncomp->memory_address_limit)
+ limit = min(limit, ncomp->memory_address_limit);
+ break;
+
+ case ACPI_IORT_NODE_PCI_ROOT_COMPLEX:
+ rc = (struct acpi_iort_root_complex
Re: [PATCH v3 7/8] arm64: mm: Set ZONE_DMA size based on early IORT scan
On Wed, Oct 14, 2020 at 09:12:09PM +0200, Nicolas Saenz Julienne wrote:
[...]
> +unsigned int __init acpi_iort_get_zone_dma_size(void)
> +{
> + struct acpi_table_iort *iort;
> + struct acpi_iort_node *node, *end;
> + acpi_status status;
> + u8 limit = 32;
> + int i;
> +
> + if (acpi_disabled)
> + return limit;
> +
> + status = acpi_get_table(ACPI_SIG_IORT, 0,
> + (struct acpi_table_header **));
> + if (ACPI_FAILURE(status))
> + return limit;
> +
> + node = ACPI_ADD_PTR(struct acpi_iort_node, iort, iort->node_offset);
> + end = ACPI_ADD_PTR(struct acpi_iort_node, iort, iort->header.length);
> +
> + for (i = 0; i < iort->node_count; i++) {
> + if (node >= end)
> + break;
> +
> + switch (node->type) {
> + struct acpi_iort_named_component *ncomp;
> + struct acpi_iort_root_complex *rc;
> +
> + case ACPI_IORT_NODE_NAMED_COMPONENT:
> + ncomp = (struct acpi_iort_named_component
> *)node->node_data;
> + if (ncomp->memory_address_limit)
> + limit = min(limit, ncomp->memory_address_limit);
> + break;
> +
> + case ACPI_IORT_NODE_PCI_ROOT_COMPLEX:
> + rc = (struct acpi_iort_root_complex *)node->node_data;
> + if (rc->memory_address_limit)
You need to add a node revision check here, see rc_dma_get_range() in
drivers/acpi/arm64/iort.c, otherwise we may be reading junk data
in older IORT tables - acpica structures are always referring to the
latest specs.
Thanks,
Lorenzo
> + limit = min(limit, rc->memory_address_limit);
> + break;
> + }
> + node = ACPI_ADD_PTR(struct acpi_iort_node, node, node->length);
> + }
> + acpi_put_table(>header);
> + return limit;
> +}
> +#endif
> diff --git a/include/linux/acpi_iort.h b/include/linux/acpi_iort.h
> index 20a32120bb88..7d2e184f0d4d 100644
> --- a/include/linux/acpi_iort.h
> +++ b/include/linux/acpi_iort.h
> @@ -38,6 +38,7 @@ void iort_dma_setup(struct device *dev, u64 *dma_addr, u64
> *size);
> const struct iommu_ops *iort_iommu_configure_id(struct device *dev,
> const u32 *id_in);
> int iort_iommu_msi_get_resv_regions(struct device *dev, struct list_head
> *head);
> +unsigned int acpi_iort_get_zone_dma_size(void);
> #else
> static inline void acpi_iort_init(void) { }
> static inline u32 iort_msi_map_id(struct device *dev, u32 id)
> @@ -55,6 +56,9 @@ static inline const struct iommu_ops
> *iort_iommu_configure_id(
> static inline
> int iort_iommu_msi_get_resv_regions(struct device *dev, struct list_head
> *head)
> { return 0; }
> +
> +static inline unsigned int acpi_iort_get_zone_dma_size(void)
> +{ return 32; }
> #endif
>
> #endif /* __ACPI_IORT_H__ */
> --
> 2.28.0
>
___
iommu mailing list
iommu@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/iommu
[PATCH v3 7/8] arm64: mm: Set ZONE_DMA size based on early IORT scan
From: Ard Biesheuvel
We recently introduced a 1 GB sized ZONE_DMA to cater for platforms
incorporating masters that can address less than 32 bits of DMA, in
particular the Raspberry Pi 4, which has 4 or 8 GB of DRAM, but has
peripherals that can only address up to 1 GB (and its PCIe host
bridge can only access the bottom 3 GB)
Instructing the DMA layer about these limitations is straight-forward,
even though we had to fix some issues regarding memory limits set in
the IORT for named components, and regarding the handling of ACPI _DMA
methods. However, the DMA layer also needs to be able to allocate
memory that is guaranteed to meet those DMA constraints, for bounce
buffering as well as allocating the backing for consistent mappings.
This is why the 1 GB ZONE_DMA was introduced recently. Unfortunately,
it turns out the having a 1 GB ZONE_DMA as well as a ZONE_DMA32 causes
problems with kdump, and potentially in other places where allocations
cannot cross zone boundaries. Therefore, we should avoid having two
separate DMA zones when possible.
So let's do an early scan of the IORT, and only create the ZONE_DMA
if we encounter any devices that need it. This puts the burden on
the firmware to describe such limitations in the IORT, which may be
redundant (and less precise) if _DMA methods are also being provided.
However, it should be noted that this situation is highly unusual for
arm64 ACPI machines. Also, the DMA subsystem still gives precedence to
the _DMA method if implemented, and so we will not lose the ability to
perform streaming DMA outside the ZONE_DMA if the _DMA method permits
it.
Cc: Jeremy Linton
Cc: Lorenzo Pieralisi
Cc: Nicolas Saenz Julienne
Cc: Rob Herring
Cc: Christoph Hellwig
Cc: Robin Murphy
Cc: Hanjun Guo
Cc: Sudeep Holla
Cc: Anshuman Khandual
Signed-off-by: Ard Biesheuvel
[nsaenz: Rebased, removed documentation change, warnings and add
declaration in acpi_iort.h]
Signed-off-by: Nicolas Saenz Julienne
---
arch/arm64/mm/init.c | 6 +
drivers/acpi/arm64/iort.c | 51 +++
include/linux/acpi_iort.h | 4 +++
3 files changed, 61 insertions(+)
diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
index 97b0d2768349..f321761eedb2 100644
--- a/arch/arm64/mm/init.c
+++ b/arch/arm64/mm/init.c
@@ -29,6 +29,7 @@
#include
#include
#include
+#include
#include
#include
@@ -196,6 +197,11 @@ static void __init zone_sizes_init(unsigned long min,
unsigned long max)
#ifdef CONFIG_ZONE_DMA
zone_dma_bits = min(zone_dma_bits,
(unsigned
int)ilog2(of_dma_get_max_cpu_address(NULL)));
+
+ if (IS_ENABLED(CONFIG_ACPI))
+ zone_dma_bits = min(zone_dma_bits,
+ acpi_iort_get_zone_dma_size());
+
arm64_dma_phys_limit = max_zone_phys(zone_dma_bits);
max_zone_pfns[ZONE_DMA] = PFN_DOWN(arm64_dma_phys_limit);
#endif
diff --git a/drivers/acpi/arm64/iort.c b/drivers/acpi/arm64/iort.c
index 9929ff50c0c0..8f530bf3c03b 100644
--- a/drivers/acpi/arm64/iort.c
+++ b/drivers/acpi/arm64/iort.c
@@ -1718,3 +1718,54 @@ void __init acpi_iort_init(void)
iort_init_platform_devices();
}
+
+#ifdef CONFIG_ZONE_DMA
+/*
+ * Check the IORT whether any devices exist whose DMA mask is < 32 bits.
+ * If so, return the smallest value encountered, or 32 otherwise.
+ */
+unsigned int __init acpi_iort_get_zone_dma_size(void)
+{
+ struct acpi_table_iort *iort;
+ struct acpi_iort_node *node, *end;
+ acpi_status status;
+ u8 limit = 32;
+ int i;
+
+ if (acpi_disabled)
+ return limit;
+
+ status = acpi_get_table(ACPI_SIG_IORT, 0,
+ (struct acpi_table_header **));
+ if (ACPI_FAILURE(status))
+ return limit;
+
+ node = ACPI_ADD_PTR(struct acpi_iort_node, iort, iort->node_offset);
+ end = ACPI_ADD_PTR(struct acpi_iort_node, iort, iort->header.length);
+
+ for (i = 0; i < iort->node_count; i++) {
+ if (node >= end)
+ break;
+
+ switch (node->type) {
+ struct acpi_iort_named_component *ncomp;
+ struct acpi_iort_root_complex *rc;
+
+ case ACPI_IORT_NODE_NAMED_COMPONENT:
+ ncomp = (struct acpi_iort_named_component
*)node->node_data;
+ if (ncomp->memory_address_limit)
+ limit = min(limit, ncomp->memory_address_limit);
+ break;
+
+ case ACPI_IORT_NODE_PCI_ROOT_COMPLEX:
+ rc = (struct acpi_iort_root_complex *)node->node_data;
+ if (rc->memory_address_limit)
+ limit = min(limit, rc->memory_address_limit);
+ break;
+ }
+ node = ACPI_ADD_PTR(struct acpi_iort_node, node, node->length);
+ }
+
