From: Sean Christopherson Date: Thu, 10 Oct 2024 18:23:36 +0000 (-0700) Subject: KVM: Get writable mapping for __kvm_vcpu_map() only when necessary X-Git-Tag: v6.13-rc1~97^2~17^2~51 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=2e5fdf60a9a69971b5e642d32e09bd6b0223f47c;p=thirdparty%2Fkernel%2Flinux.git KVM: Get writable mapping for __kvm_vcpu_map() only when necessary When creating a memory map for read, don't request a writable pfn from the primary MMU. While creating read-only mappings can be theoretically slower, as they don't play nice with fast GUP due to the need to break CoW before mapping the underlying PFN, practically speaking, creating a mapping isn't a super hot path, and getting a writable mapping for reading is weird and confusing. Tested-by: Alex Bennée Signed-off-by: Sean Christopherson Tested-by: Dmitry Osipenko Signed-off-by: Paolo Bonzini Message-ID: <20241010182427.1434605-35-seanjc@google.com> --- diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index baa741c2b81c4..49ac13872e091 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -3116,7 +3116,7 @@ int __kvm_vcpu_map(struct kvm_vcpu *vcpu, gfn_t gfn, struct kvm_host_map *map, struct kvm_follow_pfn kfp = { .slot = gfn_to_memslot(vcpu->kvm, gfn), .gfn = gfn, - .flags = FOLL_WRITE, + .flags = writable ? FOLL_WRITE : 0, .refcounted_page = &map->pinned_page, .pin = true, };