Move the check that a vGPU is attacked from is_2MB_gtt_possible() to its
sole caller, ppgtt_populate_shadow_entry(). All of the paths in
ppgtt_populate_shadow_entry() eventually check for attachment by way of
intel_gvt_dma_map_guest_page(), but explicitly checking can avoid
unnecessary work and will make it more obvious that a future cleanup of
is_2MB_gtt_possible() isn't introducing a bug.
Signed-off-by: Sean Christopherson <[email protected]>
---
drivers/gpu/drm/i915/gvt/gtt.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/drivers/gpu/drm/i915/gvt/gtt.c b/drivers/gpu/drm/i915/gvt/gtt.c
index 5426a27c1b71..2aed31b497c9 100644
--- a/drivers/gpu/drm/i915/gvt/gtt.c
+++ b/drivers/gpu/drm/i915/gvt/gtt.c
@@ -1163,8 +1163,6 @@ static int is_2MB_gtt_possible(struct intel_vgpu *vgpu,
if (!HAS_PAGE_SIZES(vgpu->gvt->gt->i915, I915_GTT_PAGE_SIZE_2M))
return 0;
- if (!test_bit(INTEL_VGPU_STATUS_ATTACHED, vgpu->status))
- return -EINVAL;
pfn = gfn_to_pfn(vgpu->vfio_device.kvm, ops->get_pfn(entry));
if (is_error_noslot_pfn(pfn))
return -EINVAL;
@@ -1277,6 +1275,9 @@ static int ppgtt_populate_shadow_entry(struct intel_vgpu *vgpu,
if (!pte_ops->test_present(ge))
return 0;
+ if (!test_bit(INTEL_VGPU_STATUS_ATTACHED, vgpu->status))
+ return -EINVAL;
+
gfn = pte_ops->get_pfn(ge);
switch (ge->type) {
--
2.40.1.606.ga4b1b128d6-goog
On 5/13/2023 8:35 AM, Sean Christopherson wrote:
> Move the check that a vGPU is attacked from is_2MB_gtt_possible() to its
> sole caller, ppgtt_populate_shadow_entry(). All of the paths in
> ppgtt_populate_shadow_entry() eventually check for attachment by way of
> intel_gvt_dma_map_guest_page(), but explicitly checking can avoid
> unnecessary work and will make it more obvious that a future cleanup of
> is_2MB_gtt_possible() isn't introducing a bug.
>
It might be better move this check to shadow_ppgtt_mm() which is used
in both shadow page table creation and pinning path so that the path
can bail out even earlier when creating a shadow page table but a vGPU
has not been attached to KVM yet.
> Signed-off-by: Sean Christopherson <[email protected]>
> ---
> drivers/gpu/drm/i915/gvt/gtt.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/gvt/gtt.c b/drivers/gpu/drm/i915/gvt/gtt.c
> index 5426a27c1b71..2aed31b497c9 100644
> --- a/drivers/gpu/drm/i915/gvt/gtt.c
> +++ b/drivers/gpu/drm/i915/gvt/gtt.c
> @@ -1163,8 +1163,6 @@ static int is_2MB_gtt_possible(struct intel_vgpu *vgpu,
> if (!HAS_PAGE_SIZES(vgpu->gvt->gt->i915, I915_GTT_PAGE_SIZE_2M))
> return 0;
>
> - if (!test_bit(INTEL_VGPU_STATUS_ATTACHED, vgpu->status))
> - return -EINVAL;
> pfn = gfn_to_pfn(vgpu->vfio_device.kvm, ops->get_pfn(entry));
> if (is_error_noslot_pfn(pfn))
> return -EINVAL;
> @@ -1277,6 +1275,9 @@ static int ppgtt_populate_shadow_entry(struct intel_vgpu *vgpu,
> if (!pte_ops->test_present(ge))
> return 0;
>
> + if (!test_bit(INTEL_VGPU_STATUS_ATTACHED, vgpu->status))
> + return -EINVAL;
> +
> gfn = pte_ops->get_pfn(ge);
>
> switch (ge->type) {
On Mon, May 15, 2023, Zhi A Wang wrote:
> On 5/13/2023 8:35 AM, Sean Christopherson wrote:
> > Move the check that a vGPU is attacked from is_2MB_gtt_possible() to its
> > sole caller, ppgtt_populate_shadow_entry(). All of the paths in
> > ppgtt_populate_shadow_entry() eventually check for attachment by way of
> > intel_gvt_dma_map_guest_page(), but explicitly checking can avoid
> > unnecessary work and will make it more obvious that a future cleanup of
> > is_2MB_gtt_possible() isn't introducing a bug.
> >
>
> It might be better move this check to shadow_ppgtt_mm() which is used
> in both shadow page table creation and pinning path so that the path
> can bail out even earlier when creating a shadow page table but a vGPU
> has not been attached to KVM yet.
Ah, yes, that'll work. I traced through all of the paths that lead to
ppgtt_populate_shadow_entry(), and shadow_ppgtt_mm() is the only caller that isn't
already gated by INTEL_VGPU_STATUS_ATTACHED or INTEL_VGPU_STATUS_ACTIVE (ACTIVE
is set iff ATTACHED is set).
I'll move the check up to shadow_ppgtt_mm() in the next version.
Thanks!
workload_thread() <= pick_next_workload() => INTEL_VGPU_STATUS_ACTIVE
|
-> dispatch_workload()
|
|-> prepare_workload()
|
-> intel_vgpu_sync_oos_pages()
| |
| |-> ppgtt_set_guest_page_sync()
| |
| |-> sync_oos_page()
| |
| |-> ppgtt_populate_shadow_entry()
|
|-> intel_vgpu_flush_post_shadow()
|
1: |-> ppgtt_handle_guest_write_page_table()
|
|-> ppgtt_handle_guest_entry_add()
|
2: | -> ppgtt_populate_spt_by_guest_entry()
| |
| |-> ppgtt_populate_spt()
| |
| |-> ppgtt_populate_shadow_entry()
| |
| |-> ppgtt_populate_spt_by_guest_entry() [see 2]
|
|-> ppgtt_populate_shadow_entry()
kvmgt_page_track_write() <= KVM callback => INTEL_VGPU_STATUS_ATTACHED
|
|-> intel_vgpu_page_track_handler()
|
|-> ppgtt_write_protection_handler()
|
|-> ppgtt_handle_guest_write_page_table_bytes()
|
|-> ppgtt_handle_guest_write_page_table() [see 1]