On 3/17/2023 1:32 AM, Joao Martins wrote: > GALog exists to propagate interrupts into all vCPUs in the system when > interrupts are marked as non running (e.g. when vCPUs aren't running). A > GALog overflow happens when there's in no space in the log to record the > GATag of the interrupt. So when the GALOverflow condition happens, the > GALog queue is processed and the GALog is restarted, as the IOMMU > manual indicates in section "2.7.4 Guest Virtual APIC Log Restart > Procedure": > > | * Wait until MMIO Offset 2020h[GALogRun]=0b so that all request > | entries are completed as circumstances allow. GALogRun must be 0b to > | modify the guest virtual APIC log registers safely. > | * Write MMIO Offset 0018h[GALogEn]=0b. > | * As necessary, change the following values (e.g., to relocate or > | resize the guest virtual APIC event log): > | - the Guest Virtual APIC Log Base Address Register > | [MMIO Offset 00E0h], > | - the Guest Virtual APIC Log Head Pointer Register > | [MMIO Offset 2040h][GALogHead], and > | - the Guest Virtual APIC Log Tail Pointer Register > | [MMIO Offset 2048h][GALogTail]. > | * Write MMIO Offset 2020h[GALOverflow] = 1b to clear the bit (W1C). > | * Write MMIO Offset 0018h[GALogEn] = 1b, and either set > | MMIO Offset 0018h[GAIntEn] to enable the GA log interrupt or clear > | the bit to disable it. > > Failing to handle the GALog overflow means that none of the VFs (in any > guest) will work with IOMMU AVIC forcing the user to power cycle the > host. When handling the event it resumes the GALog without resizing > much like how it is done in the event handler overflow. The > [MMIO Offset 2020h][GALOverflow] bit might be set in status register > without the [MMIO Offset 2020h][GAInt] bit, so when deciding to poll > for GA events (to clear space in the galog), also check the overflow > bit. > > [suravee: Check for GAOverflow without GAInt, toggle CONTROL_GAINT_EN] > Co-developed-by: Suravee Suthikulpanit <suravee.suthikulpanit@xxxxxxx> > Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@xxxxxxx> > Signed-off-by: Joao Martins <joao.m.martins@xxxxxxxxxx> Patch looks good to me. Reviewed-by: Vasant Hegde <vasant.hegde@xxxxxxx> -Vasant
