[PATCH v4.1] drm/i915/gvt: Explicitly check that vGPU is attached before shadowing

From: Sean Christopherson
Date: Tue Aug 01 2023 - 19:05:38 EST


Move the check that a vGPU is attached from is_2MB_gtt_possible() all the
way up to shadow_ppgtt_mm() to avoid unnecessary work, and to make it more
obvious that a future cleanup of is_2MB_gtt_possible() isn't introducing a
bug.

is_2MB_gtt_possible() has only one caller, ppgtt_populate_shadow_entry(),
and all paths in ppgtt_populate_shadow_entry() eventually check for
attachment by way of intel_gvt_dma_map_guest_page().

And of the paths that lead to ppgtt_populate_shadow_entry(),
shadow_ppgtt_mm() is the only one that doesn't already check for
INTEL_VGPU_STATUS_ACTIVE or INTEL_VGPU_STATUS_ATTACHED.

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]

Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
---

v4.1:

- Actually make the code do what the changelog says. [Yan]
- Fix a typo in the changelog. [Yan]

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..de6a484090d7 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;
@@ -1827,6 +1825,9 @@ static int shadow_ppgtt_mm(struct intel_vgpu_mm *mm)
if (mm->ppgtt_mm.shadowed)
return 0;

+ if (!test_bit(INTEL_VGPU_STATUS_ATTACHED, vgpu->status))
+ return -EINVAL;
+
mm->ppgtt_mm.shadowed = true;

for (index = 0; index < ARRAY_SIZE(mm->ppgtt_mm.guest_pdps); index++) {

base-commit: 03e8f77e106ba1d2fd980f8b38339dad33333a07
--
2.41.0.585.gd2178a4bd4-goog