RE: [PATCH 10/12] swiotlb: add a SWIOTLB_ANY flag to lift the low memory restriction
From: Dongli Zhang Sent: Friday, March 4, 2022 10:28 AM > > Hi Michael, > > On 3/4/22 10:12 AM, Michael Kelley (LINUX) wrote: > > From: Christoph Hellwig Sent: Tuesday, March 1, 2022 2:53 AM > >> > >> Power SVM wants to allocate a swiotlb buffer that is not restricted to low > >> memory for > >> the trusted hypervisor scheme. Consolidate the support for this into the > >> swiotlb_init > >> interface by adding a new flag. > > > > Hyper-V Isolated VMs want to do the same thing of not restricting the > > swiotlb > > buffer to low memory. That's what Tianyu Lan's patch set[1] is proposing. > > Hyper-V synthetic devices have no DMA addressing limitations, and the > > likelihood of using a PCI pass-thru device with addressing limitations in an > > Isolated VM seems vanishingly small. > > > > So could use of the SWIOTLB_ANY flag be generalized? Let Hyper-V init > > code set the flag before swiotlb_init() is called. Or provide a CONFIG > > variable that Hyper-V Isolated VMs could set. > > I used to send 64-bit swiotlb, while at that time people thought it was the > same > as Restricted DMA patchset. > > https://lore.kernel.org/all/20210203233709.19819-1-dongli.zh...@oracle.com/ > > However, I do not think Restricted DMA patchset is going to supports 64-bit > (or > high memory) DMA. Is this what you are looking for? Yes, it looks like your patchset would do what we want for Hyper-V Isolated VMs, but it is a more complex solution than is needed. My assertion is that in some environments, such as Hyper-V Isolated VMs, we're willing to assume all devices are 64-bit DMA capable, and to stop carrying the legacy baggage. Bounce buffering is used for a different scenario (memory encryption), and the bounce buffers can be allocated in high memory. There's no need for a 2nd swiotlb buffer. Michael
Re: [PATCH 10/12] swiotlb: add a SWIOTLB_ANY flag to lift the low memory restriction
Hi Michael,
On 3/4/22 10:12 AM, Michael Kelley (LINUX) wrote:
> From: Christoph Hellwig Sent: Tuesday, March 1, 2022 2:53 AM
>>
>> Power SVM wants to allocate a swiotlb buffer that is not restricted to low
>> memory for
>> the trusted hypervisor scheme. Consolidate the support for this into the
>> swiotlb_init
>> interface by adding a new flag.
>
> Hyper-V Isolated VMs want to do the same thing of not restricting the swiotlb
> buffer to low memory. That's what Tianyu Lan's patch set[1] is proposing.
> Hyper-V synthetic devices have no DMA addressing limitations, and the
> likelihood of using a PCI pass-thru device with addressing limitations in an
> Isolated VM seems vanishingly small.
>
> So could use of the SWIOTLB_ANY flag be generalized? Let Hyper-V init
> code set the flag before swiotlb_init() is called. Or provide a CONFIG
> variable that Hyper-V Isolated VMs could set.
I used to send 64-bit swiotlb, while at that time people thought it was the same
as Restricted DMA patchset.
https://lore.kernel.org/all/20210203233709.19819-1-dongli.zh...@oracle.com/
However, I do not think Restricted DMA patchset is going to supports 64-bit (or
high memory) DMA. Is this what you are looking for?
Dongli Zhang
>
> Michael
>
> [1]
> https://urldefense.com/v3/__https://lore.kernel.org/lkml/20220209122302.213882-1-ltyker...@gmail.com/__;!!ACWV5N9M2RV99hQ!fUx4fMgdQIrqJDDy-pbv9xMeyHX0rC6iN8176LWjylI2_lsjy03gysm0-lAbV1Yb7_g$
>
>
>>
>> Signed-off-by: Christoph Hellwig
>> ---
>> arch/powerpc/include/asm/svm.h | 4
>> arch/powerpc/include/asm/swiotlb.h | 1 +
>> arch/powerpc/kernel/dma-swiotlb.c| 1 +
>> arch/powerpc/mm/mem.c| 5 +
>> arch/powerpc/platforms/pseries/svm.c | 26 +-
>> include/linux/swiotlb.h | 1 +
>> kernel/dma/swiotlb.c | 9 +++--
>> 7 files changed, 12 insertions(+), 35 deletions(-)
>>
>> diff --git a/arch/powerpc/include/asm/svm.h b/arch/powerpc/include/asm/svm.h
>> index 7546402d796af..85580b30aba48 100644
>> --- a/arch/powerpc/include/asm/svm.h
>> +++ b/arch/powerpc/include/asm/svm.h
>> @@ -15,8 +15,6 @@ static inline bool is_secure_guest(void)
>> return mfmsr() & MSR_S;
>> }
>>
>> -void __init svm_swiotlb_init(void);
>> -
>> void dtl_cache_ctor(void *addr);
>> #define get_dtl_cache_ctor()(is_secure_guest() ? dtl_cache_ctor :
>> NULL)
>>
>> @@ -27,8 +25,6 @@ static inline bool is_secure_guest(void)
>> return false;
>> }
>>
>> -static inline void svm_swiotlb_init(void) {}
>> -
>> #define get_dtl_cache_ctor() NULL
>>
>> #endif /* CONFIG_PPC_SVM */
>> diff --git a/arch/powerpc/include/asm/swiotlb.h
>> b/arch/powerpc/include/asm/swiotlb.h
>> index 3c1a1cd161286..4203b5e0a88ed 100644
>> --- a/arch/powerpc/include/asm/swiotlb.h
>> +++ b/arch/powerpc/include/asm/swiotlb.h
>> @@ -9,6 +9,7 @@
>> #include
>>
>> extern unsigned int ppc_swiotlb_enable;
>> +extern unsigned int ppc_swiotlb_flags;
>>
>> #ifdef CONFIG_SWIOTLB
>> void swiotlb_detect_4g(void);
>> diff --git a/arch/powerpc/kernel/dma-swiotlb.c b/arch/powerpc/kernel/dma-
>> swiotlb.c
>> index fc7816126a401..ba256c37bcc0f 100644
>> --- a/arch/powerpc/kernel/dma-swiotlb.c
>> +++ b/arch/powerpc/kernel/dma-swiotlb.c
>> @@ -10,6 +10,7 @@
>> #include
>>
>> unsigned int ppc_swiotlb_enable;
>> +unsigned int ppc_swiotlb_flags;
>>
>> void __init swiotlb_detect_4g(void)
>> {
>> diff --git a/arch/powerpc/mm/mem.c b/arch/powerpc/mm/mem.c index
>> e1519e2edc656..a4d65418c30a9 100644
>> --- a/arch/powerpc/mm/mem.c
>> +++ b/arch/powerpc/mm/mem.c
>> @@ -249,10 +249,7 @@ void __init mem_init(void)
>> * back to to-down.
>> */
>> memblock_set_bottom_up(true);
>> -if (is_secure_guest())
>> -svm_swiotlb_init();
>> -else
>> -swiotlb_init(ppc_swiotlb_enable, 0);
>> +swiotlb_init(ppc_swiotlb_enable, ppc_swiotlb_flags);
>> #endif
>>
>> high_memory = (void *) __va(max_low_pfn * PAGE_SIZE); diff --git
>> a/arch/powerpc/platforms/pseries/svm.c b/arch/powerpc/platforms/pseries/svm.c
>> index c5228f4969eb2..3b4045d508ec8 100644
>> --- a/arch/powerpc/platforms/pseries/svm.c
>> +++ b/arch/powerpc/platforms/pseries/svm.c
>> @@ -28,7 +28,7 @@ static int __init init_svm(void)
>> * need to use the SWIOTLB buffer for DMA even if dma_capable() says
>> * otherwise.
>> */
>> -swiotlb_force = SWIOTLB_FORCE;
>> +ppc_swiotlb_flags |= SWIOTLB_ANY | SWIOTLB_FORCE;
>>
>> /* Share the SWIOTLB buffer with the host. */
>> swiotlb_update_mem_attributes();
>> @@ -37,30 +37,6 @@ static int __init init_svm(void) }
>> machine_early_initcall(pseries,
>> init_svm);
>>
>> -/*
>> - * Initialize SWIOTLB. Essentially the same as swiotlb_init(), except that
>> it
>> - * can allocate the buffer anywhere in memory. Since the hypervisor doesn't
>> have
>> - * any addressing limitation, we don't need to allocate it in low addresses.
>> - */
>> -void __init
RE: [PATCH 10/12] swiotlb: add a SWIOTLB_ANY flag to lift the low memory restriction
From: Christoph Hellwig Sent: Tuesday, March 1, 2022 2:53 AM
>
> Power SVM wants to allocate a swiotlb buffer that is not restricted to low
> memory for
> the trusted hypervisor scheme. Consolidate the support for this into the
> swiotlb_init
> interface by adding a new flag.
Hyper-V Isolated VMs want to do the same thing of not restricting the swiotlb
buffer to low memory. That's what Tianyu Lan's patch set[1] is proposing.
Hyper-V synthetic devices have no DMA addressing limitations, and the
likelihood of using a PCI pass-thru device with addressing limitations in an
Isolated VM seems vanishingly small.
So could use of the SWIOTLB_ANY flag be generalized? Let Hyper-V init
code set the flag before swiotlb_init() is called. Or provide a CONFIG
variable that Hyper-V Isolated VMs could set.
Michael
[1] https://lore.kernel.org/lkml/20220209122302.213882-1-ltyker...@gmail.com/
>
> Signed-off-by: Christoph Hellwig
> ---
> arch/powerpc/include/asm/svm.h | 4
> arch/powerpc/include/asm/swiotlb.h | 1 +
> arch/powerpc/kernel/dma-swiotlb.c| 1 +
> arch/powerpc/mm/mem.c| 5 +
> arch/powerpc/platforms/pseries/svm.c | 26 +-
> include/linux/swiotlb.h | 1 +
> kernel/dma/swiotlb.c | 9 +++--
> 7 files changed, 12 insertions(+), 35 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/svm.h b/arch/powerpc/include/asm/svm.h
> index 7546402d796af..85580b30aba48 100644
> --- a/arch/powerpc/include/asm/svm.h
> +++ b/arch/powerpc/include/asm/svm.h
> @@ -15,8 +15,6 @@ static inline bool is_secure_guest(void)
> return mfmsr() & MSR_S;
> }
>
> -void __init svm_swiotlb_init(void);
> -
> void dtl_cache_ctor(void *addr);
> #define get_dtl_cache_ctor() (is_secure_guest() ? dtl_cache_ctor : NULL)
>
> @@ -27,8 +25,6 @@ static inline bool is_secure_guest(void)
> return false;
> }
>
> -static inline void svm_swiotlb_init(void) {}
> -
> #define get_dtl_cache_ctor() NULL
>
> #endif /* CONFIG_PPC_SVM */
> diff --git a/arch/powerpc/include/asm/swiotlb.h
> b/arch/powerpc/include/asm/swiotlb.h
> index 3c1a1cd161286..4203b5e0a88ed 100644
> --- a/arch/powerpc/include/asm/swiotlb.h
> +++ b/arch/powerpc/include/asm/swiotlb.h
> @@ -9,6 +9,7 @@
> #include
>
> extern unsigned int ppc_swiotlb_enable;
> +extern unsigned int ppc_swiotlb_flags;
>
> #ifdef CONFIG_SWIOTLB
> void swiotlb_detect_4g(void);
> diff --git a/arch/powerpc/kernel/dma-swiotlb.c b/arch/powerpc/kernel/dma-
> swiotlb.c
> index fc7816126a401..ba256c37bcc0f 100644
> --- a/arch/powerpc/kernel/dma-swiotlb.c
> +++ b/arch/powerpc/kernel/dma-swiotlb.c
> @@ -10,6 +10,7 @@
> #include
>
> unsigned int ppc_swiotlb_enable;
> +unsigned int ppc_swiotlb_flags;
>
> void __init swiotlb_detect_4g(void)
> {
> diff --git a/arch/powerpc/mm/mem.c b/arch/powerpc/mm/mem.c index
> e1519e2edc656..a4d65418c30a9 100644
> --- a/arch/powerpc/mm/mem.c
> +++ b/arch/powerpc/mm/mem.c
> @@ -249,10 +249,7 @@ void __init mem_init(void)
>* back to to-down.
>*/
> memblock_set_bottom_up(true);
> - if (is_secure_guest())
> - svm_swiotlb_init();
> - else
> - swiotlb_init(ppc_swiotlb_enable, 0);
> + swiotlb_init(ppc_swiotlb_enable, ppc_swiotlb_flags);
> #endif
>
> high_memory = (void *) __va(max_low_pfn * PAGE_SIZE); diff --git
> a/arch/powerpc/platforms/pseries/svm.c b/arch/powerpc/platforms/pseries/svm.c
> index c5228f4969eb2..3b4045d508ec8 100644
> --- a/arch/powerpc/platforms/pseries/svm.c
> +++ b/arch/powerpc/platforms/pseries/svm.c
> @@ -28,7 +28,7 @@ static int __init init_svm(void)
>* need to use the SWIOTLB buffer for DMA even if dma_capable() says
>* otherwise.
>*/
> - swiotlb_force = SWIOTLB_FORCE;
> + ppc_swiotlb_flags |= SWIOTLB_ANY | SWIOTLB_FORCE;
>
> /* Share the SWIOTLB buffer with the host. */
> swiotlb_update_mem_attributes();
> @@ -37,30 +37,6 @@ static int __init init_svm(void) }
> machine_early_initcall(pseries,
> init_svm);
>
> -/*
> - * Initialize SWIOTLB. Essentially the same as swiotlb_init(), except that it
> - * can allocate the buffer anywhere in memory. Since the hypervisor doesn't
> have
> - * any addressing limitation, we don't need to allocate it in low addresses.
> - */
> -void __init svm_swiotlb_init(void)
> -{
> - unsigned char *vstart;
> - unsigned long bytes, io_tlb_nslabs;
> -
> - io_tlb_nslabs = (swiotlb_size_or_default() >> IO_TLB_SHIFT);
> - io_tlb_nslabs = ALIGN(io_tlb_nslabs, IO_TLB_SEGSIZE);
> -
> - bytes = io_tlb_nslabs << IO_TLB_SHIFT;
> -
> - vstart = memblock_alloc(PAGE_ALIGN(bytes), PAGE_SIZE);
> - if (vstart && !swiotlb_init_with_tbl(vstart, io_tlb_nslabs, false))
> - return;
> -
> -
> - memblock_free(vstart, PAGE_ALIGN(io_tlb_nslabs << IO_TLB_SHIFT));
> - panic("SVM: Cannot allocate SWIOTLB buffer");
> -}
> -
> int set_memory_encrypted(unsigned long addr, int
[PATCH 10/12] swiotlb: add a SWIOTLB_ANY flag to lift the low memory restriction
Power SVM wants to allocate a swiotlb buffer that is not restricted to
low memory for the trusted hypervisor scheme. Consolidate the support
for this into the swiotlb_init interface by adding a new flag.
Signed-off-by: Christoph Hellwig
---
arch/powerpc/include/asm/svm.h | 4
arch/powerpc/include/asm/swiotlb.h | 1 +
arch/powerpc/kernel/dma-swiotlb.c| 1 +
arch/powerpc/mm/mem.c| 5 +
arch/powerpc/platforms/pseries/svm.c | 26 +-
include/linux/swiotlb.h | 1 +
kernel/dma/swiotlb.c | 9 +++--
7 files changed, 12 insertions(+), 35 deletions(-)
diff --git a/arch/powerpc/include/asm/svm.h b/arch/powerpc/include/asm/svm.h
index 7546402d796af..85580b30aba48 100644
--- a/arch/powerpc/include/asm/svm.h
+++ b/arch/powerpc/include/asm/svm.h
@@ -15,8 +15,6 @@ static inline bool is_secure_guest(void)
return mfmsr() & MSR_S;
}
-void __init svm_swiotlb_init(void);
-
void dtl_cache_ctor(void *addr);
#define get_dtl_cache_ctor() (is_secure_guest() ? dtl_cache_ctor : NULL)
@@ -27,8 +25,6 @@ static inline bool is_secure_guest(void)
return false;
}
-static inline void svm_swiotlb_init(void) {}
-
#define get_dtl_cache_ctor() NULL
#endif /* CONFIG_PPC_SVM */
diff --git a/arch/powerpc/include/asm/swiotlb.h
b/arch/powerpc/include/asm/swiotlb.h
index 3c1a1cd161286..4203b5e0a88ed 100644
--- a/arch/powerpc/include/asm/swiotlb.h
+++ b/arch/powerpc/include/asm/swiotlb.h
@@ -9,6 +9,7 @@
#include
extern unsigned int ppc_swiotlb_enable;
+extern unsigned int ppc_swiotlb_flags;
#ifdef CONFIG_SWIOTLB
void swiotlb_detect_4g(void);
diff --git a/arch/powerpc/kernel/dma-swiotlb.c
b/arch/powerpc/kernel/dma-swiotlb.c
index fc7816126a401..ba256c37bcc0f 100644
--- a/arch/powerpc/kernel/dma-swiotlb.c
+++ b/arch/powerpc/kernel/dma-swiotlb.c
@@ -10,6 +10,7 @@
#include
unsigned int ppc_swiotlb_enable;
+unsigned int ppc_swiotlb_flags;
void __init swiotlb_detect_4g(void)
{
diff --git a/arch/powerpc/mm/mem.c b/arch/powerpc/mm/mem.c
index e1519e2edc656..a4d65418c30a9 100644
--- a/arch/powerpc/mm/mem.c
+++ b/arch/powerpc/mm/mem.c
@@ -249,10 +249,7 @@ void __init mem_init(void)
* back to to-down.
*/
memblock_set_bottom_up(true);
- if (is_secure_guest())
- svm_swiotlb_init();
- else
- swiotlb_init(ppc_swiotlb_enable, 0);
+ swiotlb_init(ppc_swiotlb_enable, ppc_swiotlb_flags);
#endif
high_memory = (void *) __va(max_low_pfn * PAGE_SIZE);
diff --git a/arch/powerpc/platforms/pseries/svm.c
b/arch/powerpc/platforms/pseries/svm.c
index c5228f4969eb2..3b4045d508ec8 100644
--- a/arch/powerpc/platforms/pseries/svm.c
+++ b/arch/powerpc/platforms/pseries/svm.c
@@ -28,7 +28,7 @@ static int __init init_svm(void)
* need to use the SWIOTLB buffer for DMA even if dma_capable() says
* otherwise.
*/
- swiotlb_force = SWIOTLB_FORCE;
+ ppc_swiotlb_flags |= SWIOTLB_ANY | SWIOTLB_FORCE;
/* Share the SWIOTLB buffer with the host. */
swiotlb_update_mem_attributes();
@@ -37,30 +37,6 @@ static int __init init_svm(void)
}
machine_early_initcall(pseries, init_svm);
-/*
- * Initialize SWIOTLB. Essentially the same as swiotlb_init(), except that it
- * can allocate the buffer anywhere in memory. Since the hypervisor doesn't
have
- * any addressing limitation, we don't need to allocate it in low addresses.
- */
-void __init svm_swiotlb_init(void)
-{
- unsigned char *vstart;
- unsigned long bytes, io_tlb_nslabs;
-
- io_tlb_nslabs = (swiotlb_size_or_default() >> IO_TLB_SHIFT);
- io_tlb_nslabs = ALIGN(io_tlb_nslabs, IO_TLB_SEGSIZE);
-
- bytes = io_tlb_nslabs << IO_TLB_SHIFT;
-
- vstart = memblock_alloc(PAGE_ALIGN(bytes), PAGE_SIZE);
- if (vstart && !swiotlb_init_with_tbl(vstart, io_tlb_nslabs, false))
- return;
-
-
- memblock_free(vstart, PAGE_ALIGN(io_tlb_nslabs << IO_TLB_SHIFT));
- panic("SVM: Cannot allocate SWIOTLB buffer");
-}
-
int set_memory_encrypted(unsigned long addr, int numpages)
{
if (!cc_platform_has(CC_ATTR_MEM_ENCRYPT))
diff --git a/include/linux/swiotlb.h b/include/linux/swiotlb.h
index dcecf953f7997..ee655f2e4d28b 100644
--- a/include/linux/swiotlb.h
+++ b/include/linux/swiotlb.h
@@ -15,6 +15,7 @@ struct scatterlist;
#define SWIOTLB_VERBOSE(1 << 0) /* verbose initialization */
#define SWIOTLB_FORCE (1 << 1) /* force bounce buffering */
+#define SWIOTLB_ANY(1 << 2) /* allow any memory for the buffer */
/*
* Maximum allowable number of contiguous slabs to map,
diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
index 1a40c71c4d51a..77cf73dc20a78 100644
--- a/kernel/dma/swiotlb.c
+++ b/kernel/dma/swiotlb.c
@@ -275,8 +275,13 @@ void __init swiotlb_init(bool addressing_limit, unsigned
int flags)
if (swiotlb_force_disable)
return;
- /* Get IO TLB
