Re: [PATCH v2 1/2] PCI: vmd: Assign VMD IRQ domain before enumeration

[Bjorn Helgaas <helgaas@kernel.org>]

On Wed, Mar 30, 2022 at 08:54:15AM -0700, Patel, Nirmal wrote:
> On 3/29/2022 4:27 PM, Dan Williams wrote:
> > On Tue, Mar 29, 2022 at 3:48 PM Patel, Nirmal
> > <nirmal.patel@linux.intel.com> wrote:
> >> On 3/16/2022 8:51 AM, Nirmal Patel wrote:
> >>> From: Nirmal Patel <nirmal.patel@linux.intel.com>
> >>>
> >>> VMD creates and assigns a separate IRQ domain only when MSI remapping is
> >>> enabled. For example VMD-MSI. But VMD doesn't assign IRQ domain when
> >>> MSI remapping is disabled resulting child devices getting default
> >>> PCI-MSI IRQ domain. Now when interrupt remapping is enabled by
> >>> intel-iommu all the PCI devices are assigned INTEL-IR-MSI domain
> >>> including VMD endpoints. But devices behind VMD get PCI-MSI IRQ domain
> >>> when VMD create a root bus and configures child devices.
> >>>
> >>> As a result DMAR errors were observed when interrupt remapping was
> >>> enabled on Intel Icelake CPUs. For instance:
> >>>
> >>>   DMAR: DRHD: handling fault status reg 2
> >>>   DMAR: [INTR-REMAP] Request device [0xe2:0x00.0] fault index 0xa00 [fault reason 0x25] Blocked a compatibility format interrupt request
> >>>
> >>> Acked-by: Dan Williams <dan.j.williams@intel.com>
> >>> Signed-off-by: Nirmal Patel <nirmal.patel@linux.intel.com>
> >>> ---
> >>>  drivers/pci/controller/vmd.c | 2 ++
> >>>  1 file changed, 2 insertions(+)
> >>>
> >>> diff --git a/drivers/pci/controller/vmd.c b/drivers/pci/controller/vmd.c
> >>> index cc166c683638..3a6570e5b765 100644
> >>> --- a/drivers/pci/controller/vmd.c
> >>> +++ b/drivers/pci/controller/vmd.c
> >>> @@ -853,6 +853,8 @@ static int vmd_enable_domain(struct vmd_dev *vmd, unsigned long features)
> >>>       vmd_attach_resources(vmd);
> >>>       if (vmd->irq_domain)
> >>>               dev_set_msi_domain(&vmd->bus->dev, vmd->irq_domain);
> >>> +     else
> >>> +             dev_set_msi_domain(&vmd->bus->dev, dev_get_msi_domain(&vmd->dev->dev));
> >>>
> >>>       vmd_acpi_begin();
> >>>
> >> Gentle ping!
> > It helps to be explicit when you send a patch and a follow-up ping.
> > Are you asking Lorenzo to take this? Is this urgent such that Bjorn
> > should consider taking it directly? The changelog notes what happens,
> > but not the severity of end user visible impact. The merge window is
> > presently open so the natural inclination is to just wait until that
> > closes to circle back to outstanding patches.
> 
> This patch removes a flag that bypasses MSI disable feature of VMD and
> improves the performance. So it would be nice if the patch gets accepted
> sooner. I tend to send follow-up ping after a week or so if I do not get any
> feedback and to allow it to get accepted in time.

There are only a few days left in the v5.18 merge window, so unless
it's an emergency, this would be v5.19 material.

This claims to be a v2, but I missed the v1, and the lore archives [1]
seem incomplete.  Maybe the v1 (and maybe the cover letter?) were HTML
or got lost for some other reason?

Bjorn

[1] https://lore.kernel.org/all/?q=f%3Anirmal.patel