Re: [Qemu-devel] [PATCH] vfio/pci-quirks: Set non-zero GMS memory size for IGD

[Alex Williamson <alex.williamson@redhat.com>]

[cc +Zhang, Xiong Y]


Intel, any comments?


On Mon, 24 Jul 2017 15:07:29 +0300
Dmitry Fleytman <dmitry@daynix.com> wrote:

> There is a claim that GMS memory is unused however
> Intel Windows 10 drivers starting from V.4534 (10/7/2016)
> allocate extra ~4G memory when GMS size set to 0.
> 
> This patch fixes this issue by seting IGD GMS memory
> size to minimum by changing default value of x-igd-gms
> device parameter.
> 
> Signed-off-by: Dmitry Fleytman <dmitry@daynix.com>
> ---
>  hw/vfio/pci-quirks.c | 13 +++++++++----
>  hw/vfio/pci.c        |  2 +-
>  2 files changed, 10 insertions(+), 5 deletions(-)
> 
> diff --git a/hw/vfio/pci-quirks.c b/hw/vfio/pci-quirks.c
> index 349085e..197cb90 100644
> --- a/hw/vfio/pci-quirks.c
> +++ b/hw/vfio/pci-quirks.c
> @@ -1527,10 +1527,15 @@ static void vfio_probe_igd_bar4_quirk(VFIOPCIDevice *vdev, int nr)
>      }
>  
>      /*
> -     * Assume we have no GMS memory, but allow it to be overrided by device
> -     * option (experimental).  The spec doesn't actually allow zero GMS when
> -     * when IVD (IGD VGA Disable) is clear, but the claim is that it's unused,
> -     * so let's not waste VM memory for it.
> +     * There is a claim that GMS memory is unused and we want to waste for it
> +     * as less VM memory as possible, however Intel Windows 10 drivers starting
> +     * from V.4534 (10/7/2016) allocate extra ~4G memory when GMS size set to 0.
> +     * The spec as well doesn't actually allow zero GMS when IVD
> +     * (IGD VGA Disable) is clear.
> +     *
> +     * Therefore we set GMS memory size to minimal by default via device
> +     * option x-igd-gms (experimental) and allow further tweaking of this
> +     * parameter.
>       */
>      gmch &= ~((gen < 8 ? 0x1f : 0xff) << (gen < 8 ? 3 : 8));
>  
> diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c
> index d4051cb..bda07b7 100644
> --- a/hw/vfio/pci.c
> +++ b/hw/vfio/pci.c
> @@ -2982,7 +2982,7 @@ static Property vfio_pci_dev_properties[] = {
>                         sub_vendor_id, PCI_ANY_ID),
>      DEFINE_PROP_UINT32("x-pci-sub-device-id", VFIOPCIDevice,
>                         sub_device_id, PCI_ANY_ID),
> -    DEFINE_PROP_UINT32("x-igd-gms", VFIOPCIDevice, igd_gms, 0),
> +    DEFINE_PROP_UINT32("x-igd-gms", VFIOPCIDevice, igd_gms, 1),
>      /*
>       * TODO - support passed fds... is this necessary?
>       * DEFINE_PROP_STRING("vfiofd", VFIOPCIDevice, vfiofd_name),