Re: [PATCH v4 4/7] iommu/amd: Program guest-mode IRTEs for GAPPI wakeup when IRTE[IsRun] = 0
Vasant Hegde <[email protected]>
| Newsgroups | dev.linux.lists.linux-coco,dev.linux.lists.iommu,org.kernel.vger.kvm,org.kernel.vger.linux-doc,org.kernel.vger.linux-kernel |
|---|---|
| Message-ID | <[email protected]> |
On 8/21/2026 11:26 AM, Sairaj Kodilkar wrote: > Guest APIC Physical Processor Interrupt (GAPPI) is an alternative to the > GA log for notifying the host when a device interrupt targets a > non-running vCPU (IRTE[IsRun] = 0). Per the AMD IOMMU specification [1] > (section 2.2.5.4), with GAPPI enabled the IOMMU delivers a physical APIC > interrupt to the CPU described by IRTE[Destination], using > IRTE[GATag][7:0] as the vector, while still updating the guest vAPIC > backing page IRR as usual. > > The AMD IOMMU also allows suppressing GAPPI interrupts using the > IRTE[GAPPIDis] bit when the GAPPIDisSup feature is available in > extended feature register 2. The AMD IOMMU driver sets this bit when > the wakeup_intr flag is not set by KVM. > > Note: amd_iommu_gappi is currently false; a later patch enables it via > the kernel command line. > > [1] https://docs.amd.com/v/u/en-US/48882_3.11_IOMMU_PUB > > Signed-off-by: Sairaj Kodilkar <[email protected]> Reviewed-by: Vasant Hegde <[email protected]> -Vasant