Re: [Qemu-devel] [RFC ppc-next PATCH 3/6] memory: add memory_region_to_address()
On 14.02.2013, at 07:31, Scott Wood wrote:
This is useful for when a user of the memory region API needs to
communicate the absolute bus address to something outside QEMU
(in particular, KVM).
Signed-off-by: Scott Wood scottw...@freescale.com
Peter, how does the VGIC implementation handle this?
Alex
---
include/exec/memory.h |9 +
memory.c | 38 ++
2 files changed, 43 insertions(+), 4 deletions(-)
diff --git a/include/exec/memory.h b/include/exec/memory.h
index 2322732..b800391 100644
--- a/include/exec/memory.h
+++ b/include/exec/memory.h
@@ -892,6 +892,15 @@ void *address_space_map(AddressSpace *as, hwaddr addr,
void address_space_unmap(AddressSpace *as, void *buffer, hwaddr len,
int is_write, hwaddr access_len);
+/* memory_region_to_address: Find the full address of the start of the
+ * given #MemoryRegion, ignoring aliases. There is no guarantee
+ * that the #MemoryRegion is actually visible at this address, if
+ * there are overlapping regions.
+ *
+ * @mr: #MemoryRegion being queried
+ * @asp: if non-NULL, returns the #AddressSpace @mr is mapped in, if any
+ */
+hwaddr memory_region_to_address(MemoryRegion *mr, AddressSpace **asp);
#endif
diff --git a/memory.c b/memory.c
index cd7d5e0..0099f12 100644
--- a/memory.c
+++ b/memory.c
@@ -453,21 +453,51 @@ const IORangeOps memory_region_iorange_ops = {
.destructor = memory_region_iorange_destructor,
};
-static AddressSpace *memory_region_to_address_space(MemoryRegion *mr)
+static AddressSpace *memory_region_root_to_address_space(MemoryRegion *mr)
{
AddressSpace *as;
-while (mr-parent) {
-mr = mr-parent;
-}
QTAILQ_FOREACH(as, address_spaces, address_spaces_link) {
if (mr == as-root) {
return as;
}
}
+
+return NULL;
+}
+
+static AddressSpace *memory_region_to_address_space(MemoryRegion *mr)
+{
+AddressSpace *as;
+
+while (mr-parent) {
+mr = mr-parent;
+}
+
+as = memory_region_root_to_address_space(mr);
+if (as) {
+return as;
+}
+
abort();
}
+hwaddr memory_region_to_address(MemoryRegion *mr, AddressSpace **asp)
+{
+hwaddr addr = mr-addr;
+
+while (mr-parent) {
+mr = mr-parent;
+addr += mr-addr;
+}
+
+if (asp) {
+*asp = memory_region_root_to_address_space(mr);
+}
+
+return addr;
+}
+
/* Render a memory region into the global view. Ranges in @view obscure
* ranges in @mr.
*/
--
1.7.9.5
Re: [Qemu-devel] [RFC ppc-next PATCH 3/6] memory: add memory_region_to_address()
On 21 March 2013 08:31, Alexander Graf ag...@suse.de wrote: On 14.02.2013, at 07:31, Scott Wood wrote: This is useful for when a user of the memory region API needs to communicate the absolute bus address to something outside QEMU (in particular, KVM). Signed-off-by: Scott Wood scottw...@freescale.com Peter, how does the VGIC implementation handle this? Check kvm_arm_register_device() in target-arm/kvm.c. Basically the VGIC device model calls this function to say tell the kernel where this MemoryRegion is in the system address space, when it eventually gets mapped. The code in kvm.c uses the memory system's Notifier API to get a callback when the region is mapped into an address space, which it uses to track the offset in the address space. Finally, we use a machine init notifier so that just before everything finally starts we can make the KVM ioctls to say here is where everything lives. I think this is a pretty neat way of doing it because it means neither the interrupt controller device nor the board model really need to care about the kernel being told where things are mapped; it's all abstracted out into kvm.c. If your interrupt controller can be moved around at runtime that's probably also handlable, but the ARM code just unregisters its notifiers at machine init because the GIC can't move. (I think the code assumes the device only gets mapped into one address space; this could easily be fixed if it's not true at some point in the future.) thanks -- PMM
Re: [Qemu-devel] [RFC ppc-next PATCH 3/6] memory: add memory_region_to_address()
On 21.03.2013, at 11:53, Peter Maydell wrote: On 21 March 2013 08:31, Alexander Graf ag...@suse.de wrote: On 14.02.2013, at 07:31, Scott Wood wrote: This is useful for when a user of the memory region API needs to communicate the absolute bus address to something outside QEMU (in particular, KVM). Signed-off-by: Scott Wood scottw...@freescale.com Peter, how does the VGIC implementation handle this? Check kvm_arm_register_device() in target-arm/kvm.c. Basically the VGIC device model calls this function to say tell the kernel where this MemoryRegion is in the system address space, when it eventually gets mapped. The code in kvm.c uses the memory system's Notifier API to get a callback when the region is mapped into an address space, which it uses to track the offset in the address space. Finally, we use a machine init notifier so that just before everything finally starts we can make the KVM ioctls to say here is where everything lives. Same thing here. The question is how the kvm-vgic code in QEMU finds out where it got mapped to. Scott adds this patch to do this, but I'd assume you have some other way :) Alex I think this is a pretty neat way of doing it because it means neither the interrupt controller device nor the board model really need to care about the kernel being told where things are mapped; it's all abstracted out into kvm.c. If your interrupt controller can be moved around at runtime that's probably also handlable, but the ARM code just unregisters its notifiers at machine init because the GIC can't move. (I think the code assumes the device only gets mapped into one address space; this could easily be fixed if it's not true at some point in the future.) thanks -- PMM
Re: [Qemu-devel] [RFC ppc-next PATCH 3/6] memory: add memory_region_to_address()
On 21 March 2013 10:59, Alexander Graf ag...@suse.de wrote: On 21.03.2013, at 11:53, Peter Maydell wrote: Check kvm_arm_register_device() in target-arm/kvm.c. Basically the VGIC device model calls this function to say tell the kernel where this MemoryRegion is in the system address space, when it eventually gets mapped. The code in kvm.c uses the memory system's Notifier API to get a callback when the region is mapped into an address space, which it uses to track the offset in the address space. Finally, we use a machine init notifier so that just before everything finally starts we can make the KVM ioctls to say here is where everything lives. Same thing here. The question is how the kvm-vgic code in QEMU finds out where it got mapped to. Scott adds this patch to do this, but I'd assume you have some other way :) Hmm? The kvm-vgic code in QEMU doesn't need to know where it lives. We have to tell the kernel so it can map its bits of registers in at the right place, that's all. -- PMM
Re: [Qemu-devel] [RFC ppc-next PATCH 3/6] memory: add memory_region_to_address()
On 21 March 2013 11:05, Alexander Graf ag...@suse.de wrote: On 21.03.2013, at 12:01, Peter Maydell wrote: On 21 March 2013 10:59, Alexander Graf ag...@suse.de wrote: On 21.03.2013, at 11:53, Peter Maydell wrote: Check kvm_arm_register_device() in target-arm/kvm.c. Basically the VGIC device model calls this function to say tell the kernel where this MemoryRegion is in the system address space, when it eventually gets mapped. The code in kvm.c uses the memory system's Notifier API to get a callback when the region is mapped into an address space, which it uses to track the offset in the address space. Finally, we use a machine init notifier so that just before everything finally starts we can make the KVM ioctls to say here is where everything lives. Same thing here. The question is how the kvm-vgic code in QEMU finds out where it got mapped to. Scott adds this patch to do this, but I'd assume you have some other way :) Hmm? The kvm-vgic code in QEMU doesn't need to know where it lives. We have to tell the kernel so it can map its bits of registers in at the right place, that's all. The kvm-vgic code in QEMU needs to tell the kernel, no? For that, it needs to know what to tell the kernel. No. As I explained earlier, all the kvm-vgic code needs to do is call kvm_arm_register_device(). That code in kvm.c then takes care of telling the kernel. hw/kvm/arm_gic.c itself never knows or needs to know where it's mapped. This is the whole point of the mechanism involving notifiers. This patch adds a function that allows kvm-openpic to fetch its base flat address from the MemoryListener. This sounds to me like the wrong way to do it -- it's board models that decide where devices are mapped and the device code itself shouldn't have to know where it has been mapped. -- PMM
Re: [Qemu-devel] [RFC ppc-next PATCH 3/6] memory: add memory_region_to_address()
On 21.03.2013, at 12:09, Peter Maydell wrote:
On 21 March 2013 11:05, Alexander Graf ag...@suse.de wrote:
On 21.03.2013, at 12:01, Peter Maydell wrote:
On 21 March 2013 10:59, Alexander Graf ag...@suse.de wrote:
On 21.03.2013, at 11:53, Peter Maydell wrote:
Check kvm_arm_register_device() in target-arm/kvm.c. Basically
the VGIC device model calls this function to say tell the kernel
where this MemoryRegion is in the system address space, when it
eventually gets mapped. The code in kvm.c uses the memory system's
Notifier API to get a callback when the region is mapped into
an address space, which it uses to track the offset in the
address space. Finally, we use a machine init notifier so that
just before everything finally starts we can make the KVM ioctls
to say here is where everything lives.
Same thing here. The question is how the kvm-vgic code in QEMU
finds out where it got mapped to. Scott adds this patch to do
this, but I'd assume you have some other way :)
Hmm? The kvm-vgic code in QEMU doesn't need to know where it
lives. We have to tell the kernel so it can map its bits of
registers in at the right place, that's all.
The kvm-vgic code in QEMU needs to tell the kernel, no? For
that, it needs to know what to tell the kernel.
No. As I explained earlier, all the kvm-vgic code needs to do
is call kvm_arm_register_device(). That code in kvm.c then takes
care of telling the kernel. hw/kvm/arm_gic.c itself never knows or
needs to know where it's mapped. This is the whole point of the
mechanism involving notifiers.
I fully disagree. Code that talks to the in-kernel device should live in
hw/kvm/device.c, not in some random target-XXX/kvm.c file. Of course the
board defines where the device gets mapped to, but the communication with the
in-kernel device bits should really be contained to the device itself.
So this is the function that gets invoked on ARM:
static void kvm_arm_machine_init_done(Notifier *notifier, void *data)
{
KVMDevice *kd, *tkd;
memory_listener_unregister(devlistener);
QSLIST_FOREACH_SAFE(kd, kvm_devices_head, entries, tkd) {
if (kd-kda.addr != -1) {
if (kvm_vm_ioctl(kvm_state, KVM_ARM_SET_DEVICE_ADDR,
kd-kda) 0) {
fprintf(stderr, KVM_ARM_SET_DEVICE_ADDRESS failed: %s\n,
strerror(errno));
abort();
}
}
g_free(kd);
}
}
This only goes one level deep, right? So if you ever have to nest the VGIC
inside of another MemoryRegion, this will break, right?
Alex
This patch adds a function that allows kvm-openpic to fetch its
base flat address from the MemoryListener.
This sounds to me like the wrong way to do it -- it's board
models that decide where devices are mapped and the device
code itself shouldn't have to know where it has been mapped.
-- PMM
Re: [Qemu-devel] [RFC ppc-next PATCH 3/6] memory: add memory_region_to_address()
On 21 March 2013 11:14, Alexander Graf ag...@suse.de wrote:
On 21.03.2013, at 12:09, Peter Maydell wrote:
On 21 March 2013 11:05, Alexander Graf ag...@suse.de wrote:
On 21.03.2013, at 12:01, Peter Maydell wrote:
On 21 March 2013 10:59, Alexander Graf ag...@suse.de wrote:
On 21.03.2013, at 11:53, Peter Maydell wrote:
Check kvm_arm_register_device() in target-arm/kvm.c. Basically
the VGIC device model calls this function to say tell the kernel
where this MemoryRegion is in the system address space, when it
eventually gets mapped. The code in kvm.c uses the memory system's
Notifier API to get a callback when the region is mapped into
an address space, which it uses to track the offset in the
address space. Finally, we use a machine init notifier so that
just before everything finally starts we can make the KVM ioctls
to say here is where everything lives.
Same thing here. The question is how the kvm-vgic code in QEMU
finds out where it got mapped to. Scott adds this patch to do
this, but I'd assume you have some other way :)
Hmm? The kvm-vgic code in QEMU doesn't need to know where it
lives. We have to tell the kernel so it can map its bits of
registers in at the right place, that's all.
The kvm-vgic code in QEMU needs to tell the kernel, no? For
that, it needs to know what to tell the kernel.
No. As I explained earlier, all the kvm-vgic code needs to do
is call kvm_arm_register_device(). That code in kvm.c then takes
care of telling the kernel. hw/kvm/arm_gic.c itself never knows or
needs to know where it's mapped. This is the whole point of the
mechanism involving notifiers.
I fully disagree. Code that talks to the in-kernel device should
live in hw/kvm/device.c, not in some random target-XXX/kvm.c file.
The code in kvm.c is entirely generic -- it provides a mechanism
for a device to say this memory region is kernel ID X and it will
want to know where it lives. The kvm.c code will work for any device
with a memory mapped region, whether it's the GIC or something else.
Of course the board defines where the device gets mapped to, but
the communication with the in-kernel device bits should really be
contained to the device itself.
You're arguing that every device should implement its own set
of notifier functions so it can get called back when its memory
regions are finally mapped, just so it can make a non-device-specific
KVM ioctl? The obvious thing to do is abstract that functionality
out.
So this is the function that gets invoked on ARM:
static void kvm_arm_machine_init_done(Notifier *notifier, void *data)
{
KVMDevice *kd, *tkd;
memory_listener_unregister(devlistener);
QSLIST_FOREACH_SAFE(kd, kvm_devices_head, entries, tkd) {
if (kd-kda.addr != -1) {
if (kvm_vm_ioctl(kvm_state, KVM_ARM_SET_DEVICE_ADDR,
kd-kda) 0) {
fprintf(stderr, KVM_ARM_SET_DEVICE_ADDRESS failed: %s\n,
strerror(errno));
abort();
}
}
g_free(kd);
}
}
This only goes one level deep, right? So if you ever have to nest the
VGIC inside of another MemoryRegion, this will break, right?
We already nest the VGIC inside another memory region (the a15mpcore
container), and it works fine. This function is just iterating through
everything any device asked me to tell the kernel about.
-- PMM
Re: [Qemu-devel] [RFC ppc-next PATCH 3/6] memory: add memory_region_to_address()
On 21.03.2013, at 12:01, Peter Maydell wrote: On 21 March 2013 10:59, Alexander Graf ag...@suse.de wrote: On 21.03.2013, at 11:53, Peter Maydell wrote: Check kvm_arm_register_device() in target-arm/kvm.c. Basically the VGIC device model calls this function to say tell the kernel where this MemoryRegion is in the system address space, when it eventually gets mapped. The code in kvm.c uses the memory system's Notifier API to get a callback when the region is mapped into an address space, which it uses to track the offset in the address space. Finally, we use a machine init notifier so that just before everything finally starts we can make the KVM ioctls to say here is where everything lives. Same thing here. The question is how the kvm-vgic code in QEMU finds out where it got mapped to. Scott adds this patch to do this, but I'd assume you have some other way :) Hmm? The kvm-vgic code in QEMU doesn't need to know where it lives. We have to tell the kernel so it can map its bits of registers in at the right place, that's all. The kvm-vgic code in QEMU needs to tell the kernel, no? For that, it needs to know what to tell the kernel. This patch adds a function that allows kvm-openpic to fetch its base flat address from the MemoryListener. I was wondering whether either this patch is superfluous or you guys had an awkward MemoryListener handler :) Alex
Re: [Qemu-devel] [RFC ppc-next PATCH 3/6] memory: add memory_region_to_address()
On 21.03.2013, at 12:22, Peter Maydell wrote:
On 21 March 2013 11:14, Alexander Graf ag...@suse.de wrote:
On 21.03.2013, at 12:09, Peter Maydell wrote:
On 21 March 2013 11:05, Alexander Graf ag...@suse.de wrote:
On 21.03.2013, at 12:01, Peter Maydell wrote:
On 21 March 2013 10:59, Alexander Graf ag...@suse.de wrote:
On 21.03.2013, at 11:53, Peter Maydell wrote:
Check kvm_arm_register_device() in target-arm/kvm.c. Basically
the VGIC device model calls this function to say tell the kernel
where this MemoryRegion is in the system address space, when it
eventually gets mapped. The code in kvm.c uses the memory system's
Notifier API to get a callback when the region is mapped into
an address space, which it uses to track the offset in the
address space. Finally, we use a machine init notifier so that
just before everything finally starts we can make the KVM ioctls
to say here is where everything lives.
Same thing here. The question is how the kvm-vgic code in QEMU
finds out where it got mapped to. Scott adds this patch to do
this, but I'd assume you have some other way :)
Hmm? The kvm-vgic code in QEMU doesn't need to know where it
lives. We have to tell the kernel so it can map its bits of
registers in at the right place, that's all.
The kvm-vgic code in QEMU needs to tell the kernel, no? For
that, it needs to know what to tell the kernel.
No. As I explained earlier, all the kvm-vgic code needs to do
is call kvm_arm_register_device(). That code in kvm.c then takes
care of telling the kernel. hw/kvm/arm_gic.c itself never knows or
needs to know where it's mapped. This is the whole point of the
mechanism involving notifiers.
I fully disagree. Code that talks to the in-kernel device should
live in hw/kvm/device.c, not in some random target-XXX/kvm.c file.
The code in kvm.c is entirely generic -- it provides a mechanism
for a device to say this memory region is kernel ID X and it will
want to know where it lives. The kvm.c code will work for any device
with a memory mapped region, whether it's the GIC or something else.
Of course the board defines where the device gets mapped to, but
the communication with the in-kernel device bits should really be
contained to the device itself.
You're arguing that every device should implement its own set
of notifier functions so it can get called back when its memory
regions are finally mapped, just so it can make a non-device-specific
KVM ioctl? The obvious thing to do is abstract that functionality
out.
What I'm arguing is that every device should look as if it was a QEMU device.
Devices that happen to live in KVM, should still make a significant effort to
expose themselves to the board model as if they were QEMU devices.
So yes, I think the device model should at least register the memory listener,
because only the device model knows what its memory regions would map to in
KVM's world. Not all devices have a single flat region. Some have more than one.
Whether we have a helper function in (generic) kvm.c that can call a (generic)
ioctl to set a device's region X is a different matter. I'd be open to that if
it makes sense.
So this is the function that gets invoked on ARM:
static void kvm_arm_machine_init_done(Notifier *notifier, void *data)
{
KVMDevice *kd, *tkd;
memory_listener_unregister(devlistener);
QSLIST_FOREACH_SAFE(kd, kvm_devices_head, entries, tkd) {
if (kd-kda.addr != -1) {
if (kvm_vm_ioctl(kvm_state, KVM_ARM_SET_DEVICE_ADDR,
kd-kda) 0) {
fprintf(stderr, KVM_ARM_SET_DEVICE_ADDRESS failed: %s\n,
strerror(errno));
abort();
}
}
g_free(kd);
}
}
This only goes one level deep, right? So if you ever have to nest the
VGIC inside of another MemoryRegion, this will break, right?
We already nest the VGIC inside another memory region (the a15mpcore
container), and it works fine. This function is just iterating through
everything any device asked me to tell the kernel about.
So kda is the real physical offset? I'm having a hard time reading that code
:). According to this function:
static void kvm_arm_devlistener_add(MemoryListener *listener,
MemoryRegionSection *section)
{
KVMDevice *kd;
QSLIST_FOREACH(kd, kvm_devices_head, entries) {
if (section-mr == kd-mr) {
kd-kda.addr = section-offset_within_address_space;
}
}
}
it's only the offset within its parent region, which would mean it's broken, no?
Alex
Re: [Qemu-devel] [RFC ppc-next PATCH 3/6] memory: add memory_region_to_address()
On 21 March 2013 11:29, Alexander Graf ag...@suse.de wrote:
On 21.03.2013, at 12:22, Peter Maydell wrote:
We already nest the VGIC inside another memory region (the a15mpcore
container), and it works fine. This function is just iterating through
everything any device asked me to tell the kernel about.
So kda is the real physical offset? I'm having a hard time reading that code
:). According to this function:
static void kvm_arm_devlistener_add(MemoryListener *listener,
MemoryRegionSection *section)
{
KVMDevice *kd;
QSLIST_FOREACH(kd, kvm_devices_head, entries) {
if (section-mr == kd-mr) {
kd-kda.addr = section-offset_within_address_space;
}
}
}
it's only the offset within its parent region, which would mean it's broken,
no?
Address spaces are not the same thing as memory regions :-)
The only address space involved here is the system address space.
(As I say, we currently assume we only get mapped into one address
space, but that could be fixed if necessary.)
-- PMM
Re: [Qemu-devel] [RFC ppc-next PATCH 3/6] memory: add memory_region_to_address()
On 21.03.2013, at 12:32, Peter Maydell wrote:
On 21 March 2013 11:29, Alexander Graf ag...@suse.de wrote:
On 21.03.2013, at 12:22, Peter Maydell wrote:
We already nest the VGIC inside another memory region (the a15mpcore
container), and it works fine. This function is just iterating through
everything any device asked me to tell the kernel about.
So kda is the real physical offset? I'm having a hard time reading that code
:). According to this function:
static void kvm_arm_devlistener_add(MemoryListener *listener,
MemoryRegionSection *section)
{
KVMDevice *kd;
QSLIST_FOREACH(kd, kvm_devices_head, entries) {
if (section-mr == kd-mr) {
kd-kda.addr = section-offset_within_address_space;
}
}
}
it's only the offset within its parent region, which would mean it's broken,
no?
Address spaces are not the same thing as memory regions :-)
The only address space involved here is the system address space.
(As I say, we currently assume we only get mapped into one address
space, but that could be fixed if necessary.)
Interesting. Oh well, I'll leave that one to Scott to figure out ;).
So what if I want to write an in-kernel IDE PIO accelerator? Or even better
yet: An AHCI accelerator that has one MMIO BAR and another PIO BAR that can be
remapped by the guest at any time?
The distinction on whether a region is handled by KVM really needs to be done
by the device model.
Alex
Re: [Qemu-devel] [RFC ppc-next PATCH 3/6] memory: add memory_region_to_address()
On 21 March 2013 11:38, Alexander Graf ag...@suse.de wrote:
On 21.03.2013, at 12:32, Peter Maydell wrote:
On 21 March 2013 11:29, Alexander Graf ag...@suse.de wrote:
On 21.03.2013, at 12:22, Peter Maydell wrote:
We already nest the VGIC inside another memory region (the a15mpcore
container), and it works fine. This function is just iterating through
everything any device asked me to tell the kernel about.
So kda is the real physical offset? I'm having a hard time reading that
code :). According to this function:
static void kvm_arm_devlistener_add(MemoryListener *listener,
MemoryRegionSection *section)
{
KVMDevice *kd;
QSLIST_FOREACH(kd, kvm_devices_head, entries) {
if (section-mr == kd-mr) {
kd-kda.addr = section-offset_within_address_space;
}
}
}
it's only the offset within its parent region, which would mean it's
broken, no?
Address spaces are not the same thing as memory regions :-)
The only address space involved here is the system address space.
(As I say, we currently assume we only get mapped into one address
space, but that could be fixed if necessary.)
Interesting. Oh well, I'll leave that one to Scott to figure out ;).
So what if I want to write an in-kernel IDE PIO accelerator?
Have the QEMU end of that device call (your equivalent of)
kvm_arm_register_device(), and provide a 'reserved' mmio region to
its users; the kernel end implements the standard 'tell me where I live'
ioctl; that's it.
Or even better yet: An AHCI accelerator that has one MMIO BAR and
another PIO BAR that can be remapped by the guest at any time?
Guest remappable KVM regions would require enhancements, yes (it's
not like we have an existing mechanism for doing that on any
architecture at the moment). The principle of implementing the
mechanics of this in common code still holds, probably even more
so for the increased complexity.
The distinction on whether a region is handled by KVM really needs
to be done by the device model.
It is -- the device model is what calls kvm_arm_register_device().
It's just the mechanics of how do we tell the kernel the right
address for this region at the point when we know it that are
handled in kvm.c.
-- PMM
Re: [Qemu-devel] [RFC ppc-next PATCH 3/6] memory: add memory_region_to_address()
On 21.03.2013, at 12:44, Peter Maydell wrote:
On 21 March 2013 11:38, Alexander Graf ag...@suse.de wrote:
On 21.03.2013, at 12:32, Peter Maydell wrote:
On 21 March 2013 11:29, Alexander Graf ag...@suse.de wrote:
On 21.03.2013, at 12:22, Peter Maydell wrote:
We already nest the VGIC inside another memory region (the a15mpcore
container), and it works fine. This function is just iterating through
everything any device asked me to tell the kernel about.
So kda is the real physical offset? I'm having a hard time reading that
code :). According to this function:
static void kvm_arm_devlistener_add(MemoryListener *listener,
MemoryRegionSection *section)
{
KVMDevice *kd;
QSLIST_FOREACH(kd, kvm_devices_head, entries) {
if (section-mr == kd-mr) {
kd-kda.addr = section-offset_within_address_space;
}
}
}
it's only the offset within its parent region, which would mean it's
broken, no?
Address spaces are not the same thing as memory regions :-)
The only address space involved here is the system address space.
(As I say, we currently assume we only get mapped into one address
space, but that could be fixed if necessary.)
Interesting. Oh well, I'll leave that one to Scott to figure out ;).
So what if I want to write an in-kernel IDE PIO accelerator?
Have the QEMU end of that device call (your equivalent of)
kvm_arm_register_device(), and provide a 'reserved' mmio region to
its users; the kernel end implements the standard 'tell me where I live'
ioctl; that's it.
Or even better yet: An AHCI accelerator that has one MMIO BAR and
another PIO BAR that can be remapped by the guest at any time?
Guest remappable KVM regions would require enhancements, yes (it's
not like we have an existing mechanism for doing that on any
architecture at the moment). The principle of implementing the
mechanics of this in common code still holds, probably even more
so for the increased complexity.
The distinction on whether a region is handled by KVM really needs
to be done by the device model.
It is -- the device model is what calls kvm_arm_register_device().
It's just the mechanics of how do we tell the kernel the right
address for this region at the point when we know it that are
handled in kvm.c.
I think I'm slowly grasping what you're aiming at :). Ok, that works. You do
actually do the listener in the device model, just that you pass code
responsibility over to kvm.c.
That's perfectly valid and sounds like a good model that Scott probably wants
to follow as well :).
Alex
Re: [Qemu-devel] [RFC ppc-next PATCH 3/6] memory: add memory_region_to_address()
On 21 March 2013 11:49, Alexander Graf ag...@suse.de wrote: On 21.03.2013, at 12:44, Peter Maydell wrote: It is -- the device model is what calls kvm_arm_register_device(). It's just the mechanics of how do we tell the kernel the right address for this region at the point when we know it that are handled in kvm.c. I think I'm slowly grasping what you're aiming at :). Ok, that works. You do actually do the listener in the device model, just that you pass code responsibility over to kvm.c. That's perfectly valid and sounds like a good model that Scott probably wants to follow as well :). Yep. We were actually originally going to make the device ioctl a generic one, not an ARM one, because there really isn't anything ARM specific about it. We should probably move the code from target-arm/kvm.c into kvm-all.c with an arch hook to specify the ioctl to use (same as irq_set_ioctl) if you want to do the same approach with PPC. Re multiple regions: yes, the VGIC has several. We just divide the u32 ID into two halves, one for a device ID and one for a region ID for that device. -- PMM
