On Thu, 18 Apr 2024 11:31:21 -0400
Nirmal Patel <nirmal.patel@xxxxxxxxxxxxxxx> wrote:
> VMD MSI remapping is disabled by default for all the CPUs with 28c0
> VMD deviceID. We used to disable remapping because drives supported
> more vectors than the VMD so the performance was better without
> remapping. Now with CPUs that support more than 64 (128 VMD MSIx
> vectors for gen5) we no longer need to disable this feature.
>
> Note, pci_msix_vec_count() failure is translated to ENODEV per typical
> expectations that drivers may return ENODEV when some driver-known
> fundamental detail of the device is missing.
>
> Signed-off-by: Nirmal Patel <nirmal.patel@xxxxxxxxxxxxxxx>
> ---
> v1->v2: Updating commit message.
> v2->v3: Use VMD MSI count instead of cpu count.
> v3->v4: Updating commit message.
> ---
> drivers/pci/controller/vmd.c | 9 +++++++++
> 1 file changed, 9 insertions(+)
>
> diff --git a/drivers/pci/controller/vmd.c
> b/drivers/pci/controller/vmd.c index 769eedeb8802..ba63af70bb63 100644
> --- a/drivers/pci/controller/vmd.c
> +++ b/drivers/pci/controller/vmd.c
> @@ -34,6 +34,8 @@
> #define MB2_SHADOW_OFFSET 0x2000
> #define MB2_SHADOW_SIZE 16
>
> +#define VMD_MIN_MSI_VECTOR_COUNT 64
> +
> enum vmd_features {
> /*
> * Device may contain registers which hint the physical
> location of the @@ -807,13 +809,20 @@ static int
> vmd_enable_domain(struct vmd_dev *vmd, unsigned long features)
> sd->node = pcibus_to_node(vmd->dev->bus);
>
> + vmd->msix_count = pci_msix_vec_count(vmd->dev);
> + if (vmd->msix_count < 0)
> + return -ENODEV;
> +
> /*
> * Currently MSI remapping must be enabled in guest
> passthrough mode
> * due to some missing interrupt remapping plumbing. This is
> probably
> * acceptable because the guest is usually CPU-limited and
> MSI
> * remapping doesn't become a performance bottleneck.
> + * Disable MSI remapping only if supported by VMD hardware
> and when
> + * VMD MSI count is less than or equal to minimum MSI count.
> */
> if (!(features & VMD_FEAT_CAN_BYPASS_MSI_REMAP) ||
> + vmd->msix_count > VMD_MIN_MSI_VECTOR_COUNT ||
> offset[0] || offset[1]) {
> ret = vmd_alloc_irqs(vmd);
> if (ret)
Gentle ping!
Thanks
nirmal
