Re: [EXTERNAL] [tip: x86/apic] x86/io_apic: Cleanup trigger/polarity helpers

[Suravee Suthikulpanit]

David,

On 11/13/20 10:14 PM, David Woodhouse wrote:
> On Wed, 2020-11-11 at 14:30 -0600, Tom Lendacky wrote:
> > I had trouble cloning your tree for some reason, so just took the top
> > three patches and applied them to the tip tree. This all appears to be
> > working. I'll let the IOMMU experts take a closer look (adding Suravee).
>
> Thanks. I see Thomas has taken the first two into the tip.git x86/apic
> branch already, so we're just looking for an ack on the third. Which is
> this one...
>
>  From 49ee4fa51b8c06d14b7c4c74d15a7d76f865a8ea Mon Sep 17 00:00:00 2001
> From: David Woodhouse <dwmw@xxxxxxxxxxxx>
> Date: Wed, 11 Nov 2020 12:09:01 +0000
> Subject: [PATCH] iommu/amd: Fix IOMMU interrupt generation in X2APIC mode
>
> The AMD IOMMU has two modes for generating its own interrupts.
>
> The first is very much based on PCI MSI, and can be configured by Linux
> precisely that way. But like legacy unmapped PCI MSI it's limited to
> 8 bits of APIC ID.
>
> The second method does not use PCI MSI at all in hardawre, and instead
> configures the INTCAPXT registers in the IOMMU directly with the APIC ID
> and vector.
>
> In the latter case, the IOMMU driver would still use pci_enable_msi(),
> read back (through MMIO) the MSI message that Linux wrote to the PCI MSI
> table, then swizzle those bits into the appropriate register.
>
> Historically, this worked because__irq_compose_msi_msg() would silently
> generate an invalid MSI message with the high bits of the APIC ID in the
> high bits of the MSI address. That hack was intended only for the Intel
> IOMMU, and I recently enforced that, introducing a warning in
> __irq_msi_compose_msg() if it was invoked with an APIC ID above 255.
>
> Fix the AMD IOMMU not to depend on that hack any more, by having its own
> irqdomain and directly putting the bits from the irq_cfg into the right
> place in its ->activate() method.
>
> Fixes: 47bea873cf80 "x86/msi: Only use high bits of MSI address for DMAR unit")
> Signed-off-by: David Woodhouse <dwmw@xxxxxxxxxxxx>

I'm still working on testing this series using IO_PAGE_FAULT injection to trigger the IOMMU interrupts. I am still 
debugging some issues, and I'll keep you updated on the findings.

Thanks,
Suravee