On Tue, Jul 28, 2020 at 01:49:45PM -0600, Jon Derrick wrote:
> VMD will retransmit child device MSI/X using its own MSI/X table and
> requester-id. This limits the number of MSI/X available to the whole
> child device domain to the number of VMD MSI/X interrupts. Some VMD
> devices have a mode where this remapping can be disabled, allowing child
> device interrupts to bypass processing with the VMD MSI/X domain
> interrupt handler and going straight the child device interrupt handler,
> allowing for better performance and scaling. The requester-id still gets
> changed to the VMD endpoint's requester-id, and the interrupt remapping
> handlers have been updated to properly set IRTE for child device
> interrupts to the VMD endpoint's context.
>
> Some VMD platforms have existing production BIOS which rely on MSI/X
> remapping and won't explicitly program the MSI/X remapping bit. This
> re-enables MSI/X remapping on unload.
>
> Disabling MSI/X remapping is only available for Icelake Server and
> client VMD products.
I'm trying to button up the PCI pull request. I'm updating Lorenzo's
pci/vmd branch for other reasons, and I notice it still contains this
commit: 67b219dc3a6d ("PCI: vmd: Disable MSI/X remapping when
possible").
I want to remove "MSI/X" from the commit log and comments of that
commit because I don't know what "MSI/X" means.
Should I replace it with "MSI" or "MSI-X" or "MSI/MSI-X"? Something
else? When possible, I want to use exactly the same terminology as
the PCIe spec to avoid ambiguity.
It talks about "MSI/X table", which makes me think it should be
"MSI-X", since plain MSI does not have a table.
> Reviewed-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxx>
> Signed-off-by: Jon Derrick <jonathan.derrick@xxxxxxxxx>
> ---
> drivers/pci/controller/vmd.c | 58 +++++++++++++++++++++++++++++++-----
> 1 file changed, 50 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/pci/controller/vmd.c b/drivers/pci/controller/vmd.c
> index 3214d785fa5d..e8cde2c390b9 100644
> --- a/drivers/pci/controller/vmd.c
> +++ b/drivers/pci/controller/vmd.c
> @@ -53,6 +53,12 @@ enum vmd_features {
> * vendor-specific capability space
> */
> VMD_FEAT_HAS_MEMBAR_SHADOW_VSCAP = (1 << 2),
> +
> + /*
> + * Device remaps MSI/X transactions into its MSI/X table and requires
> + * VMD MSI domain for child device interrupt handling
> + */
> + VMD_FEAT_REMAPS_MSI = (1 << 3),
> };
>
> /*
> @@ -298,6 +304,15 @@ static struct msi_domain_info vmd_msi_domain_info = {
> .chip = &vmd_msi_controller,
> };
>
> +static void vmd_enable_msi_remapping(struct vmd_dev *vmd, bool enable)
> +{
> + u16 reg;
> +
> + pci_read_config_word(vmd->dev, PCI_REG_VMCONFIG, ®);
> + reg = enable ? (reg & ~0x2) : (reg | 0x2);
> + pci_write_config_word(vmd->dev, PCI_REG_VMCONFIG, reg);
> +}
> +
> static int vmd_create_irq_domain(struct vmd_dev *vmd)
> {
> struct fwnode_handle *fn;
> @@ -318,6 +333,13 @@ static int vmd_create_irq_domain(struct vmd_dev *vmd)
>
> static void vmd_remove_irq_domain(struct vmd_dev *vmd)
> {
> + /*
> + * Some production BIOS won't enable remapping between soft reboots.
> + * Ensure remapping is restored before unloading the driver
> + */
> + if (!vmd->msix_count)
> + vmd_enable_msi_remapping(vmd, true);
> +
> if (vmd->irq_domain) {
> struct fwnode_handle *fn = vmd->irq_domain->fwnode;
>
> @@ -606,6 +628,27 @@ static int vmd_enable_domain(struct vmd_dev *vmd, unsigned long features)
> return ret;
> }
>
> + /*
> + * 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.
> + */
> + if (features & VMD_FEAT_REMAPS_MSI || offset[0] || offset[1]) {
> + ret = vmd_alloc_irqs(vmd);
> + if (ret)
> + return ret;
> + }
> +
> + /*
> + * Disable remapping for performance if possible based on if VMD IRQs
> + * had been allocated.
> + */
> + if (vmd->msix_count)
> + vmd_enable_msi_remapping(vmd, true);
> + else
> + vmd_enable_msi_remapping(vmd, false);
> +
> /*
> * Certain VMD devices may have a root port configuration option which
> * limits the bus range to between 0-127, 128-255, or 224-255
> @@ -674,9 +717,11 @@ static int vmd_enable_domain(struct vmd_dev *vmd, unsigned long features)
>
> sd->node = pcibus_to_node(vmd->dev->bus);
>
> - ret = vmd_create_irq_domain(vmd);
> - if (ret)
> - return ret;
> + if (vmd->msix_count) {
> + ret = vmd_create_irq_domain(vmd);
> + if (ret)
> + return ret;
> + }
>
> pci_add_resource(&resources, &vmd->resources[0]);
> pci_add_resource_offset(&resources, &vmd->resources[1], offset[0]);
> @@ -738,10 +783,6 @@ static int vmd_probe(struct pci_dev *dev, const struct pci_device_id *id)
> dma_set_mask_and_coherent(&dev->dev, DMA_BIT_MASK(32)))
> return -ENODEV;
>
> - err = vmd_alloc_irqs(vmd);
> - if (err)
> - return err;
> -
> spin_lock_init(&vmd->cfg_lock);
> pci_set_drvdata(dev, vmd);
> err = vmd_enable_domain(vmd, (unsigned long) id->driver_data);
> @@ -809,7 +850,8 @@ static SIMPLE_DEV_PM_OPS(vmd_dev_pm_ops, vmd_suspend, vmd_resume);
>
> static const struct pci_device_id vmd_ids[] = {
> {PCI_DEVICE(PCI_VENDOR_ID_INTEL, PCI_DEVICE_ID_INTEL_VMD_201D),
> - .driver_data = VMD_FEAT_HAS_MEMBAR_SHADOW_VSCAP,},
> + .driver_data = VMD_FEAT_HAS_MEMBAR_SHADOW_VSCAP |
> + VMD_FEAT_REMAPS_MSI,},
> {PCI_DEVICE(PCI_VENDOR_ID_INTEL, PCI_DEVICE_ID_INTEL_VMD_28C0),
> .driver_data = VMD_FEAT_HAS_MEMBAR_SHADOW |
> VMD_FEAT_HAS_BUS_RESTRICTIONS,},
> --
> 2.27.0
>
