[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [PATCH 1/8] vfio/igd: fix GTT stolen memory size calculation for gen
From: |
Alex Williamson |
Subject: |
Re: [PATCH 1/8] vfio/igd: fix GTT stolen memory size calculation for gen 7 |
Date: |
Sun, 1 Dec 2024 22:11:29 -0700 |
On Mon, 2 Dec 2024 00:09:31 +0800
Tomita Moeko <tomitamoeko@gmail.com> wrote:
> Both intel documentation [1][2] and i915 driver shows GGMS represents
> GTT stolen memory size in multiple of 1MB, not 2MB starting from gen 8.
>
> [1]
> https://www.intel.com/content/dam/www/public/us/en/documents/datasheets/3rd-gen-core-desktop-vol-2-datasheet.pdf
> [2]
> https://www.intel.com/content/dam/www/public/us/en/documents/datasheets/4th-gen-core-family-desktop-vol-2-datasheet.pdf
>
> Signed-off-by: Tomita Moeko <tomitamoeko@gmail.com>
> ---
> hw/vfio/igd.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/hw/vfio/igd.c b/hw/vfio/igd.c
> index 4047f4f071..e40e601026 100644
> --- a/hw/vfio/igd.c
> +++ b/hw/vfio/igd.c
> @@ -268,7 +268,7 @@ static int vfio_igd_gtt_max(VFIOPCIDevice *vdev)
>
> gmch = vfio_pci_read_config(&vdev->pdev, IGD_GMCH, sizeof(gmch));
> ggms = (gmch >> (gen < 8 ? 8 : 6)) & 0x3;
> - if (gen > 6) {
> + if (gen > 7) {
> ggms = 1 << ggms;
> }
>
> @@ -678,7 +678,7 @@ void vfio_probe_igd_bar4_quirk(VFIOPCIDevice *vdev, int
> nr)
>
> /* Determine the size of stolen memory needed for GTT */
> ggms_mb = (gmch >> (gen < 8 ? 8 : 6)) & 0x3;
> - if (gen > 6) {
> + if (gen > 7) {
> ggms_mb = 1 << ggms_mb;
> }
>
I'd argue this should be rolled into patch 4. It's not really fixing
anything because igd_gen() can't return anything between 6 and 8. This
only allows for several device versions that we currently consider to
be gen 6 to align with i915 kernel driver generation by calling them
generation 7. We'd previously lumped them into generation 6 because
there's no functional difference we care about here between 6 & 7.
In the next patch you replace this '1 << ggms_mb' with '*= 2', which
would be equivalent to 'ggms_mb << 1' and matches your description that
the increment is doubled. Is there a separate bug fix that needs to be
pulled out here?
Also, please send a cover letter for any series longer than a single
patch and please configure your tools to thread the series. Thanks,
Alex
- Re: [PATCH 3/8] vfio/igd: remove unsupported device ids, (continued)