Re: [PATCH v2 2/8] drm/ttm: Remap all page faults to per process dummy page.
On 6/22/20 5:41 AM, Daniel Vetter wrote:
On Sun, Jun 21, 2020 at 02:03:02AM -0400, Andrey Grodzovsky wrote:
On device removal reroute all CPU mappings to dummy page per drm_file
instance or imported GEM object.
Signed-off-by: Andrey Grodzovsky
---
drivers/gpu/drm/ttm/ttm_bo_vm.c | 65 -
1 file changed, 57 insertions(+), 8 deletions(-)
diff --git a/drivers/gpu/drm/ttm/ttm_bo_vm.c b/drivers/gpu/drm/ttm/ttm_bo_vm.c
index 389128b..2f8bf5e 100644
--- a/drivers/gpu/drm/ttm/ttm_bo_vm.c
+++ b/drivers/gpu/drm/ttm/ttm_bo_vm.c
@@ -35,6 +35,8 @@
#include
#include
#include
+#include
+#include
#include
#include
#include
@@ -328,19 +330,66 @@ vm_fault_t ttm_bo_vm_fault(struct vm_fault *vmf)
Hm I think diff and code flow look a bit bad now. What about renaming the
current function to __ttm_bo_vm_fault and then having something like the
below:
ttm_bo_vm_fault(args) {
if (drm_dev_enter()) {
__ttm_bo_vm_fault(args);
drm_dev_exit();
} else {
drm_gem_insert_dummy_pfn();
}
}
I think drm_gem_insert_dummy_pfn(); should be portable across drivers, so
another nice point to try to unifiy drivers as much as possible.
-Daniel
pgprot_t prot;
struct ttm_buffer_object *bo = vma->vm_private_data;
vm_fault_t ret;
+ int idx;
+ struct drm_device *ddev = bo->base.dev;
- ret = ttm_bo_vm_reserve(bo, vmf);
- if (ret)
- return ret;
+ if (drm_dev_enter(ddev, &idx)) {
+ ret = ttm_bo_vm_reserve(bo, vmf);
+ if (ret)
+ goto exit;
+
+ prot = vma->vm_page_prot;
- prot = vma->vm_page_prot;
- ret = ttm_bo_vm_fault_reserved(vmf, prot, TTM_BO_VM_NUM_PREFAULT);
- if (ret == VM_FAULT_RETRY && !(vmf->flags & FAULT_FLAG_RETRY_NOWAIT))
+ ret = ttm_bo_vm_fault_reserved(vmf, prot,
TTM_BO_VM_NUM_PREFAULT);
+ if (ret == VM_FAULT_RETRY && !(vmf->flags &
FAULT_FLAG_RETRY_NOWAIT))
+ goto exit;
+
+ dma_resv_unlock(bo->base.resv);
+
+exit:
+ drm_dev_exit(idx);
return ret;
+ } else {
- dma_resv_unlock(bo->base.resv);
+ struct drm_file *file = NULL;
+ struct page *dummy_page = NULL;
+ int handle;
- return ret;
+ /* We are faulting on imported BO from dma_buf */
+ if (bo->base.dma_buf && bo->base.import_attach) {
+ dummy_page = bo->base.dummy_page;
+ /* We are faulting on non imported BO, find drm_file owning the
BO*/
Uh, we can't fish that out of the vma->vm_file pointer somehow? Or is that
one all wrong? Doing this kind of list walk looks pretty horrible.
If the vma doesn't have the right pointer I guess next option is that we
store the drm_file page in gem_bo->dummy_page, and replace it on first
export. But that's going to be tricky to track ...
For this one I hope to make all of this obsolete if Christian's suggestion from
path 1/8 about mapping
global RO dummy page for read and COW on write will be possible to implement
(testing
that indeed no memory usage explodes)
Andrey
+ } else {
+ struct drm_gem_object *gobj;
+
+ mutex_lock(&ddev->filelist_mutex);
+ list_for_each_entry(file, &ddev->filelist, lhead) {
+ spin_lock(&file->table_lock);
+ idr_for_each_entry(&file->object_idr, gobj,
handle) {
+ if (gobj == &bo->base) {
+ dummy_page = file->dummy_page;
+ break;
+ }
+ }
+ spin_unlock(&file->table_lock);
+ }
+ mutex_unlock(&ddev->filelist_mutex);
+ }
+
+ if (dummy_page) {
+ /*
+* Let do_fault complete the PTE install e.t.c using
vmf->page
+*
+* TODO - should i call free_page somewhere ?
Nah, instead don't call get_page. The page will be around as long as
there's a reference for the drm_file or gem_bo, which is longer than any
mmap. Otherwise yes this would like really badly.
+*/
+ get_page(dummy_page);
+ vmf->page = dummy_page;
+ return 0;
+ } else {
+ return VM_FAULT_SIGSEGV;
Hm that would be a kernel bug, wouldn't it? WARN_ON() required here imo.
-Daniel
+ }
+ }
}
EXPORT_SYMBOL(ttm_bo_vm_fault);
--
2.7.4
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Re: [PATCH v2 2/8] drm/ttm: Remap all page faults to per process dummy page.
On Tue, Jun 23, 2020 at 11:31:45PM -0400, Andrey Grodzovsky wrote:
>
> On 6/22/20 5:41 AM, Daniel Vetter wrote:
> > On Sun, Jun 21, 2020 at 02:03:02AM -0400, Andrey Grodzovsky wrote:
> > > On device removal reroute all CPU mappings to dummy page per drm_file
> > > instance or imported GEM object.
> > >
> > > Signed-off-by: Andrey Grodzovsky
> > > ---
> > > drivers/gpu/drm/ttm/ttm_bo_vm.c | 65
> > > -
> > > 1 file changed, 57 insertions(+), 8 deletions(-)
> > >
> > > diff --git a/drivers/gpu/drm/ttm/ttm_bo_vm.c
> > > b/drivers/gpu/drm/ttm/ttm_bo_vm.c
> > > index 389128b..2f8bf5e 100644
> > > --- a/drivers/gpu/drm/ttm/ttm_bo_vm.c
> > > +++ b/drivers/gpu/drm/ttm/ttm_bo_vm.c
> > > @@ -35,6 +35,8 @@
> > > #include
> > > #include
> > > #include
> > > +#include
> > > +#include
> > > #include
> > > #include
> > > #include
> > > @@ -328,19 +330,66 @@ vm_fault_t ttm_bo_vm_fault(struct vm_fault *vmf)
> > Hm I think diff and code flow look a bit bad now. What about renaming the
> > current function to __ttm_bo_vm_fault and then having something like the
> > below:
> >
> > ttm_bo_vm_fault(args) {
> >
> > if (drm_dev_enter()) {
> > __ttm_bo_vm_fault(args);
> > drm_dev_exit();
> > } else {
> > drm_gem_insert_dummy_pfn();
> > }
> > }
> >
> > I think drm_gem_insert_dummy_pfn(); should be portable across drivers, so
> > another nice point to try to unifiy drivers as much as possible.
> > -Daniel
> >
> > > pgprot_t prot;
> > > struct ttm_buffer_object *bo = vma->vm_private_data;
> > > vm_fault_t ret;
> > > + int idx;
> > > + struct drm_device *ddev = bo->base.dev;
> > > - ret = ttm_bo_vm_reserve(bo, vmf);
> > > - if (ret)
> > > - return ret;
> > > + if (drm_dev_enter(ddev, &idx)) {
> > > + ret = ttm_bo_vm_reserve(bo, vmf);
> > > + if (ret)
> > > + goto exit;
> > > +
> > > + prot = vma->vm_page_prot;
> > > - prot = vma->vm_page_prot;
> > > - ret = ttm_bo_vm_fault_reserved(vmf, prot, TTM_BO_VM_NUM_PREFAULT);
> > > - if (ret == VM_FAULT_RETRY && !(vmf->flags & FAULT_FLAG_RETRY_NOWAIT))
> > > + ret = ttm_bo_vm_fault_reserved(vmf, prot,
> > > TTM_BO_VM_NUM_PREFAULT);
> > > + if (ret == VM_FAULT_RETRY && !(vmf->flags &
> > > FAULT_FLAG_RETRY_NOWAIT))
> > > + goto exit;
> > > +
> > > + dma_resv_unlock(bo->base.resv);
> > > +
> > > +exit:
> > > + drm_dev_exit(idx);
> > > return ret;
> > > + } else {
> > > - dma_resv_unlock(bo->base.resv);
> > > + struct drm_file *file = NULL;
> > > + struct page *dummy_page = NULL;
> > > + int handle;
> > > - return ret;
> > > + /* We are faulting on imported BO from dma_buf */
> > > + if (bo->base.dma_buf && bo->base.import_attach) {
> > > + dummy_page = bo->base.dummy_page;
> > > + /* We are faulting on non imported BO, find drm_file owning the
> > > BO*/
> > Uh, we can't fish that out of the vma->vm_file pointer somehow? Or is that
> > one all wrong? Doing this kind of list walk looks pretty horrible.
> >
> > If the vma doesn't have the right pointer I guess next option is that we
> > store the drm_file page in gem_bo->dummy_page, and replace it on first
> > export. But that's going to be tricky to track ...
> >
> > > + } else {
> > > + struct drm_gem_object *gobj;
> > > +
> > > + mutex_lock(&ddev->filelist_mutex);
> > > + list_for_each_entry(file, &ddev->filelist, lhead) {
> > > + spin_lock(&file->table_lock);
> > > + idr_for_each_entry(&file->object_idr, gobj,
> > > handle) {
> > > + if (gobj == &bo->base) {
> > > + dummy_page = file->dummy_page;
> > > + break;
> > > + }
> > > + }
> > > + spin_unlock(&file->table_lock);
> > > + }
> > > + mutex_unlock(&ddev->filelist_mutex);
> > > + }
> > > +
> > > + if (dummy_page) {
> > > + /*
> > > + * Let do_fault complete the PTE install e.t.c using
> > > vmf->page
> > > + *
> > > + * TODO - should i call free_page somewhere ?
> > Nah, instead don't call get_page. The page will be around as long as
> > there's a reference for the drm_file or gem_bo, which is longer than any
> > mmap. Otherwise yes this would like really badly.
>
>
> So actually that was my thinking in the first place and I indeed avoided
> taking reference and this ended up
> with multiple BUG_ONs as seen bellow where refcount:-63 mapcount:-48 for a
> page are deep into negative
> values... Those warnings were gone once i added get_page(dummy) which in
Re: [PATCH v2 2/8] drm/ttm: Remap all page faults to per process dummy page.
On 6/22/20 5:41 AM, Daniel Vetter wrote:
On Sun, Jun 21, 2020 at 02:03:02AM -0400, Andrey Grodzovsky wrote:
On device removal reroute all CPU mappings to dummy page per drm_file
instance or imported GEM object.
Signed-off-by: Andrey Grodzovsky
---
drivers/gpu/drm/ttm/ttm_bo_vm.c | 65 -
1 file changed, 57 insertions(+), 8 deletions(-)
diff --git a/drivers/gpu/drm/ttm/ttm_bo_vm.c b/drivers/gpu/drm/ttm/ttm_bo_vm.c
index 389128b..2f8bf5e 100644
--- a/drivers/gpu/drm/ttm/ttm_bo_vm.c
+++ b/drivers/gpu/drm/ttm/ttm_bo_vm.c
@@ -35,6 +35,8 @@
#include
#include
#include
+#include
+#include
#include
#include
#include
@@ -328,19 +330,66 @@ vm_fault_t ttm_bo_vm_fault(struct vm_fault *vmf)
Hm I think diff and code flow look a bit bad now. What about renaming the
current function to __ttm_bo_vm_fault and then having something like the
below:
ttm_bo_vm_fault(args) {
if (drm_dev_enter()) {
__ttm_bo_vm_fault(args);
drm_dev_exit();
} else {
drm_gem_insert_dummy_pfn();
}
}
I think drm_gem_insert_dummy_pfn(); should be portable across drivers, so
another nice point to try to unifiy drivers as much as possible.
-Daniel
pgprot_t prot;
struct ttm_buffer_object *bo = vma->vm_private_data;
vm_fault_t ret;
+ int idx;
+ struct drm_device *ddev = bo->base.dev;
- ret = ttm_bo_vm_reserve(bo, vmf);
- if (ret)
- return ret;
+ if (drm_dev_enter(ddev, &idx)) {
+ ret = ttm_bo_vm_reserve(bo, vmf);
+ if (ret)
+ goto exit;
+
+ prot = vma->vm_page_prot;
- prot = vma->vm_page_prot;
- ret = ttm_bo_vm_fault_reserved(vmf, prot, TTM_BO_VM_NUM_PREFAULT);
- if (ret == VM_FAULT_RETRY && !(vmf->flags & FAULT_FLAG_RETRY_NOWAIT))
+ ret = ttm_bo_vm_fault_reserved(vmf, prot,
TTM_BO_VM_NUM_PREFAULT);
+ if (ret == VM_FAULT_RETRY && !(vmf->flags &
FAULT_FLAG_RETRY_NOWAIT))
+ goto exit;
+
+ dma_resv_unlock(bo->base.resv);
+
+exit:
+ drm_dev_exit(idx);
return ret;
+ } else {
- dma_resv_unlock(bo->base.resv);
+ struct drm_file *file = NULL;
+ struct page *dummy_page = NULL;
+ int handle;
- return ret;
+ /* We are faulting on imported BO from dma_buf */
+ if (bo->base.dma_buf && bo->base.import_attach) {
+ dummy_page = bo->base.dummy_page;
+ /* We are faulting on non imported BO, find drm_file owning the
BO*/
Uh, we can't fish that out of the vma->vm_file pointer somehow? Or is that
one all wrong? Doing this kind of list walk looks pretty horrible.
If the vma doesn't have the right pointer I guess next option is that we
store the drm_file page in gem_bo->dummy_page, and replace it on first
export. But that's going to be tricky to track ...
+ } else {
+ struct drm_gem_object *gobj;
+
+ mutex_lock(&ddev->filelist_mutex);
+ list_for_each_entry(file, &ddev->filelist, lhead) {
+ spin_lock(&file->table_lock);
+ idr_for_each_entry(&file->object_idr, gobj,
handle) {
+ if (gobj == &bo->base) {
+ dummy_page = file->dummy_page;
+ break;
+ }
+ }
+ spin_unlock(&file->table_lock);
+ }
+ mutex_unlock(&ddev->filelist_mutex);
+ }
+
+ if (dummy_page) {
+ /*
+* Let do_fault complete the PTE install e.t.c using
vmf->page
+*
+* TODO - should i call free_page somewhere ?
Nah, instead don't call get_page. The page will be around as long as
there's a reference for the drm_file or gem_bo, which is longer than any
mmap. Otherwise yes this would like really badly.
So actually that was my thinking in the first place and I indeed avoided taking
reference and this ended up
with multiple BUG_ONs as seen bellow where refcount:-63 mapcount:-48 for a page
are deep into negative
values... Those warnings were gone once i added get_page(dummy) which in my
opinion implies that there
is a page reference per each PTE and that when there is unmapping of the process
address
space and PTEs are deleted there is also put_page somewhere in mm core and the
get_page per mapping
keeps it balanced.
Jun 20 01:36:43 ubuntu-1604-test kernel: [ 98.762929] BUG: Bad page map in
process glxgear:disk$0 pte:800132284867 pmd:15aaec067
Jun 20 01:36:43 ubuntu-1604-test kerne
Re: [PATCH v2 2/8] drm/ttm: Remap all page faults to per process dummy page.
Am 21.06.20 um 08:03 schrieb Andrey Grodzovsky:
On device removal reroute all CPU mappings to dummy page per drm_file
instance or imported GEM object.
Signed-off-by: Andrey Grodzovsky
---
drivers/gpu/drm/ttm/ttm_bo_vm.c | 65 -
1 file changed, 57 insertions(+), 8 deletions(-)
diff --git a/drivers/gpu/drm/ttm/ttm_bo_vm.c b/drivers/gpu/drm/ttm/ttm_bo_vm.c
index 389128b..2f8bf5e 100644
--- a/drivers/gpu/drm/ttm/ttm_bo_vm.c
+++ b/drivers/gpu/drm/ttm/ttm_bo_vm.c
@@ -35,6 +35,8 @@
#include
#include
#include
+#include
+#include
#include
#include
#include
@@ -328,19 +330,66 @@ vm_fault_t ttm_bo_vm_fault(struct vm_fault *vmf)
pgprot_t prot;
struct ttm_buffer_object *bo = vma->vm_private_data;
vm_fault_t ret;
+ int idx;
+ struct drm_device *ddev = bo->base.dev;
- ret = ttm_bo_vm_reserve(bo, vmf);
- if (ret)
- return ret;
+ if (drm_dev_enter(ddev, &idx)) {
Better do this like if (!drm_dev_enter(...)) return ttm_bo_vm_dummy(..);
This way you can move all the dummy fault handling into a separate
function without cluttering this one here to much.
Christian.
+ ret = ttm_bo_vm_reserve(bo, vmf);
+ if (ret)
+ goto exit;
+
+ prot = vma->vm_page_prot;
- prot = vma->vm_page_prot;
- ret = ttm_bo_vm_fault_reserved(vmf, prot, TTM_BO_VM_NUM_PREFAULT);
- if (ret == VM_FAULT_RETRY && !(vmf->flags & FAULT_FLAG_RETRY_NOWAIT))
+ ret = ttm_bo_vm_fault_reserved(vmf, prot,
TTM_BO_VM_NUM_PREFAULT);
+ if (ret == VM_FAULT_RETRY && !(vmf->flags &
FAULT_FLAG_RETRY_NOWAIT))
+ goto exit;
+
+ dma_resv_unlock(bo->base.resv);
+
+exit:
+ drm_dev_exit(idx);
return ret;
+ } else {
- dma_resv_unlock(bo->base.resv);
+ struct drm_file *file = NULL;
+ struct page *dummy_page = NULL;
+ int handle;
- return ret;
+ /* We are faulting on imported BO from dma_buf */
+ if (bo->base.dma_buf && bo->base.import_attach) {
+ dummy_page = bo->base.dummy_page;
+ /* We are faulting on non imported BO, find drm_file owning the
BO*/
+ } else {
+ struct drm_gem_object *gobj;
+
+ mutex_lock(&ddev->filelist_mutex);
+ list_for_each_entry(file, &ddev->filelist, lhead) {
+ spin_lock(&file->table_lock);
+ idr_for_each_entry(&file->object_idr, gobj,
handle) {
+ if (gobj == &bo->base) {
+ dummy_page = file->dummy_page;
+ break;
+ }
+ }
+ spin_unlock(&file->table_lock);
+ }
+ mutex_unlock(&ddev->filelist_mutex);
+ }
+
+ if (dummy_page) {
+ /*
+* Let do_fault complete the PTE install e.t.c using
vmf->page
+*
+* TODO - should i call free_page somewhere ?
+*/
+ get_page(dummy_page);
+ vmf->page = dummy_page;
+ return 0;
+ } else {
+ return VM_FAULT_SIGSEGV;
+ }
+ }
}
EXPORT_SYMBOL(ttm_bo_vm_fault);
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Re: [PATCH v2 2/8] drm/ttm: Remap all page faults to per process dummy page.
On Sun, Jun 21, 2020 at 02:03:02AM -0400, Andrey Grodzovsky wrote:
> On device removal reroute all CPU mappings to dummy page per drm_file
> instance or imported GEM object.
>
> Signed-off-by: Andrey Grodzovsky
> ---
> drivers/gpu/drm/ttm/ttm_bo_vm.c | 65
> -
> 1 file changed, 57 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/gpu/drm/ttm/ttm_bo_vm.c b/drivers/gpu/drm/ttm/ttm_bo_vm.c
> index 389128b..2f8bf5e 100644
> --- a/drivers/gpu/drm/ttm/ttm_bo_vm.c
> +++ b/drivers/gpu/drm/ttm/ttm_bo_vm.c
> @@ -35,6 +35,8 @@
> #include
> #include
> #include
> +#include
> +#include
> #include
> #include
> #include
> @@ -328,19 +330,66 @@ vm_fault_t ttm_bo_vm_fault(struct vm_fault *vmf)
Hm I think diff and code flow look a bit bad now. What about renaming the
current function to __ttm_bo_vm_fault and then having something like the
below:
ttm_bo_vm_fault(args) {
if (drm_dev_enter()) {
__ttm_bo_vm_fault(args);
drm_dev_exit();
} else {
drm_gem_insert_dummy_pfn();
}
}
I think drm_gem_insert_dummy_pfn(); should be portable across drivers, so
another nice point to try to unifiy drivers as much as possible.
-Daniel
> pgprot_t prot;
> struct ttm_buffer_object *bo = vma->vm_private_data;
> vm_fault_t ret;
> + int idx;
> + struct drm_device *ddev = bo->base.dev;
>
> - ret = ttm_bo_vm_reserve(bo, vmf);
> - if (ret)
> - return ret;
> + if (drm_dev_enter(ddev, &idx)) {
> + ret = ttm_bo_vm_reserve(bo, vmf);
> + if (ret)
> + goto exit;
> +
> + prot = vma->vm_page_prot;
>
> - prot = vma->vm_page_prot;
> - ret = ttm_bo_vm_fault_reserved(vmf, prot, TTM_BO_VM_NUM_PREFAULT);
> - if (ret == VM_FAULT_RETRY && !(vmf->flags & FAULT_FLAG_RETRY_NOWAIT))
> + ret = ttm_bo_vm_fault_reserved(vmf, prot,
> TTM_BO_VM_NUM_PREFAULT);
> + if (ret == VM_FAULT_RETRY && !(vmf->flags &
> FAULT_FLAG_RETRY_NOWAIT))
> + goto exit;
> +
> + dma_resv_unlock(bo->base.resv);
> +
> +exit:
> + drm_dev_exit(idx);
> return ret;
> + } else {
>
> - dma_resv_unlock(bo->base.resv);
> + struct drm_file *file = NULL;
> + struct page *dummy_page = NULL;
> + int handle;
>
> - return ret;
> + /* We are faulting on imported BO from dma_buf */
> + if (bo->base.dma_buf && bo->base.import_attach) {
> + dummy_page = bo->base.dummy_page;
> + /* We are faulting on non imported BO, find drm_file owning the
> BO*/
Uh, we can't fish that out of the vma->vm_file pointer somehow? Or is that
one all wrong? Doing this kind of list walk looks pretty horrible.
If the vma doesn't have the right pointer I guess next option is that we
store the drm_file page in gem_bo->dummy_page, and replace it on first
export. But that's going to be tricky to track ...
> + } else {
> + struct drm_gem_object *gobj;
> +
> + mutex_lock(&ddev->filelist_mutex);
> + list_for_each_entry(file, &ddev->filelist, lhead) {
> + spin_lock(&file->table_lock);
> + idr_for_each_entry(&file->object_idr, gobj,
> handle) {
> + if (gobj == &bo->base) {
> + dummy_page = file->dummy_page;
> + break;
> + }
> + }
> + spin_unlock(&file->table_lock);
> + }
> + mutex_unlock(&ddev->filelist_mutex);
> + }
> +
> + if (dummy_page) {
> + /*
> + * Let do_fault complete the PTE install e.t.c using
> vmf->page
> + *
> + * TODO - should i call free_page somewhere ?
Nah, instead don't call get_page. The page will be around as long as
there's a reference for the drm_file or gem_bo, which is longer than any
mmap. Otherwise yes this would like really badly.
> + */
> + get_page(dummy_page);
> + vmf->page = dummy_page;
> + return 0;
> + } else {
> + return VM_FAULT_SIGSEGV;
Hm that would be a kernel bug, wouldn't it? WARN_ON() required here imo.
-Daniel
> + }
> + }
> }
> EXPORT_SYMBOL(ttm_bo_vm_fault);
>
> --
> 2.7.4
>
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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