Retry page faults without acquiring mmu_lock, and potentially even without resolving a pfn, if the gfn is covered by an active invalidation. This avoids resource and lock contention, which can be especially beneficial for preemptible kernels as KVM can get stuck bouncing mmu_lock between a vCPU and the invalidation task the vCPU is waiting on to finish. v4: - Pre-check for retry before resolving the pfn, too. [Yan] - Add a patch to fix a private/shared vs. memslot validity check priority inversion bug. - Refactor kvm_faultin_pfn() to clean up the handling of noslot faults. v3: - https://lkml.kernel.org/r/20240203003518.387220-1-seanjc%40google.com - Release the pfn, i.e. put the struct page reference if one was held, as the caller doesn't expect to get a reference on "failure". [Yuan] - Fix a typo in the comment. v2: - Introduce a dedicated helper and collapse to a single patch (because adding an unused helper would be quite silly). - Add a comment to explain the "unsafe" check in kvm_faultin_pfn(). [Kai] - Add Kai's Ack. v1: https://lore.kernel.org/all/20230825020733.2849862-1-seanjc@xxxxxxxxxx Sean Christopherson (4): KVM: x86/mmu: Retry fault before acquiring mmu_lock if mapping is changing KVM: x86/mmu: Move private vs. shared check above slot validity checks KVM: x86/mmu: Move slot checks from __kvm_faultin_pfn() to kvm_faultin_pfn() KVM: x86/mmu: Handle no-slot faults at the beginning of kvm_faultin_pfn() arch/x86/kvm/mmu/mmu.c | 134 ++++++++++++++++++++++---------- arch/x86/kvm/mmu/mmu_internal.h | 5 +- include/linux/kvm_host.h | 26 +++++++ 3 files changed, 122 insertions(+), 43 deletions(-) base-commit: 60eedcfceda9db46f1b333e5e1aa9359793f04fb -- 2.43.0.687.g38aa6559b0-goog
