On Mon, 2024-12-02 at 00:09 +0800, Tomita Moeko wrote: > CAUTION: External Email!! > 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 <tomitamo...@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) {
This seems odd. The commit message talks about gen 8 but it changes the
behaviour for gen 7 only. Additionally, ggms_mb is still shifted for gen
8 and later, so it's still increment by steps of 2 MB. Shouldn't this be
something like gen < 8?
> 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;
> }
>
Btw. you could consider adding a link to the source code of i915 too.
--
Kind regards,
Corvin
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