From 2e5fdf60a9a69971b5e642d32e09bd6b0223f47c Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Thu, 10 Oct 2024 11:23:36 -0700 Subject: KVM: Get writable mapping for __kvm_vcpu_map() only when necessary MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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> --- virt/kvm/kvm_main.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'virt/kvm') diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index baa741c2b81c..49ac13872e09 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, }; -- cgit v1.2.3