Re: [PATCH v3 00/10] Update vfio_pin/unpin_pages API

Nicolin Chen
2022-07-23T00:38:40Z

On Fri, Jul 22, 2022 at 06:18:00PM -0600, Alex Williamson wrote:
> External email: Use caution opening links or attachments
>
>
> On Fri, 22 Jul 2022 16:12:19 -0700
> Nicolin Chen <nicolinc@nvidia.com> wrote:
>
> > On Fri, Jul 22, 2022 at 04:11:29PM -0600, Alex Williamson wrote:
> >
> > > GVT-g explodes for me with this series on my Broadwell test system,
> > > continuously spewing the following:
> >
> > Thank you for running additional tests.
> >
> > > [ 47.348778] WARNING: CPU: 3 PID: 501 at drivers/vfio/vfio_iommu_type1.c:978 vfio_iommu_type1_unpin_pages+0x7b/0x100 [vfio_iommu_type1]
> >
> > > Line 978 is the WARN_ON(i != npage) line. For the cases where we don't
> > > find a matching vfio_dma, I'm seeing addresses that look maybe like
> > > we're shifting a value that's already an iova by PAGE_SHIFT somewhere.
> >
> > Hmm..I don't understand the PAGE_SHIFT part. Do you mind clarifying?
>
> The iova was a very large address for a 4GB VM with a lot of zeros on
> the low order bits, ex. 0x162459000000. Thanks,

Ah! Thanks for the hint. The following commit did a double shifting:
"vfio: Pass in starting IOVA to vfio_pin/unpin_pages AP"

And the following change should fix:
-------------------
diff --git a/drivers/gpu/drm/i915/gvt/kvmgt.c b/drivers/gpu/drm/i915/gvt/kvmgt.c
index 481dd2aeb40e..4790c7f35b88 100644
--- a/drivers/gpu/drm/i915/gvt/kvmgt.c
+++ b/drivers/gpu/drm/i915/gvt/kvmgt.c
@@ -293,7 +293,7 @@ static int gvt_dma_map_page(struct intel_vgpu *vgpu, unsigned long gfn,
if (dma_mapping_error(dev, *dma_addr)) {
gvt_vgpu_err("DMA mapping failed for pfn 0x%lx, ret %d\n",
page_to_pfn(page), ret);
- gvt_unpin_guest_page(vgpu, gfn << PAGE_SHIFT, size);
+ gvt_unpin_guest_page(vgpu, gfn, size);
return -ENOMEM;
}

@@ -306,7 +306,7 @@ static void gvt_dma_unmap_page(struct intel_vgpu *vgpu, unsigned long gfn,
struct device *dev = vgpu->gvt->gt->i915->drm.dev;

dma_unmap_page(dev, dma_addr, size, DMA_BIDIRECTIONAL);
- gvt_unpin_guest_page(vgpu, gfn << PAGE_SHIFT, size);
+ gvt_unpin_guest_page(vgpu, gfn, size);
}

static struct gvt_dma *__gvt_cache_find_dma_addr(struct intel_vgpu *vgpu,
-------------------

So, I think that I should send a v4, given that the patches aren't
officially applied?