On Thu, Nov 30, 2023, Sean Christopherson wrote: > On Fri, 27 Oct 2023 10:26:37 -0700, David Matlack wrote: > > This series reduces the impact of CLEAR_DIRTY_LOG on guest performance > > (Patch 3) and fixes 2 minor bugs found along the way (Patches 1 and 2). > > > > We've observed that guest performance can drop while userspace is > > issuing CLEAR_DIRTY_LOG ioctls and tracked down the problem to > > contention on the mmu_lock in vCPU threads. CLEAR_DIRTY_LOG holds the > > write-lock, so this isn't that surprising. We previously explored > > converting CLEAR_DIRTY_LOG to hold the read-lock [1], but that has some > > negative consequences: > > > > [...] > > Applied 1 and 2 to kvm-x86 mmu. To get traction on #3, I recommend resending it > as a standalone patch with all KVM arch maintainers Cc'd. > > [1/3] KVM: x86/mmu: Fix off-by-1 when splitting huge pages during CLEAR > https://github.com/kvm-x86/linux/commit/7cd1bf039eeb > [2/3] KVM: x86/mmu: Check for leaf SPTE when clearing dirty bit in the TDP MMU > https://github.com/kvm-x86/linux/commit/76d1492924bc Force pushed because the Fixes: in patch 1 referenced a Google-internal commit. New hashes: [1/2] KVM: x86/mmu: Fix off-by-1 when splitting huge pages during CLEAR https://github.com/kvm-x86/linux/commit/1aa4bb916808 [2/2] KVM: x86/mmu: Check for leaf SPTE when clearing dirty bit in the TDP MMU https://github.com/kvm-x86/linux/commit/45a61ebb2211
