[PATCH v13 36/85] KVM: x86: Don't fault-in APIC access page during initial allocation

Sean Christopherson
2024-10-10T18:26:07Z

Drop the gfn_to_page() lookup when installing KVM's internal memslot for
the APIC access page, as KVM doesn't need to immediately fault-in the page
now that the page isn't pinned. In the extremely unlikely event the
kernel can't allocate a 4KiB page, KVM can just as easily return -EFAULT
on the future page fault.

Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
arch/x86/kvm/lapic.c | 12 ------------
1 file changed, 12 deletions(-)

diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index 20526e4d6c62..65412640cfc7 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -2647,7 +2647,6 @@ void kvm_apic_update_apicv(struct kvm_vcpu *vcpu)

int kvm_alloc_apic_access_page(struct kvm *kvm)
{
- struct page *page;
void __user *hva;
int ret = 0;

@@ -2663,17 +2662,6 @@ int kvm_alloc_apic_access_page(struct kvm *kvm)
goto out;
}

- page = gfn_to_page(kvm, APIC_DEFAULT_PHYS_BASE >> PAGE_SHIFT);
- if (!page) {
- ret = -EFAULT;
- goto out;
- }
-
- /*
- * Do not pin the page in memory, so that memory hot-unplug
- * is able to migrate it.
- */
- put_page(page);
kvm->arch.apic_access_memslot_enabled = true;
out:
mutex_unlock(&kvm->slots_lock);
--
2.47.0.rc1.288.g06298d1525-goog