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authorSean Christopherson <seanjc@google.com>2024-10-10 11:23:36 -0700
committerPaolo Bonzini <pbonzini@redhat.com>2024-10-25 12:59:08 -0400
commit2e5fdf60a9a69971b5e642d32e09bd6b0223f47c (patch)
tree2e1ca3e5c6a9e23f56ed6dba2b010aa9815adb1e /virt
parent365e319208442a0807a96e9ea4d0b1fa338f1929 (diff)
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 <alex.bennee@linaro.org> Signed-off-by: Sean Christopherson <seanjc@google.com> Tested-by: Dmitry Osipenko <dmitry.osipenko@collabora.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Message-ID: <20241010182427.1434605-35-seanjc@google.com>
Diffstat (limited to 'virt')
-rw-r--r--virt/kvm/kvm_main.c2
1 files changed, 1 insertions, 1 deletions
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,
};