KVM: Retry fault before vmentry

When page is swapped in it is mapped into guest memory only after guest
tries to access it again and generate another fault. To save this fault
we can map it immediately since we know that guest is going to access
the page. Do it only when tdp is enabled for now. Shadow paging case is
more complicated. CR[034] and EFER registers should be switched before
doing mapping and then switched back.

Acked-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

1 files changed, 8 insertions, 8 deletions

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 4ab04de5a76a..b2c60986a7ce 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -2570,7 +2570,7 @@ static gpa_t nonpaging_gva_to_gpa_nested(struct kvm_vcpu *vcpu, gva_t vaddr,
 }
 
 static int nonpaging_page_fault(struct kvm_vcpu *vcpu, gva_t gva,
-                                u32 error_code)
+                                u32 error_code, bool no_apf)
 {
         gfn_t gfn;
         int r;
@@ -2606,8 +2606,8 @@ static bool can_do_async_pf(struct kvm_vcpu *vcpu)
         return kvm_x86_ops->interrupt_allowed(vcpu);
 }
 
-static bool try_async_pf(struct kvm_vcpu *vcpu, gfn_t gfn, gva_t gva,
-                         pfn_t *pfn)
+static bool try_async_pf(struct kvm_vcpu *vcpu, bool no_apf, gfn_t gfn,
+                         gva_t gva, pfn_t *pfn)
 {
         bool async;
 
@@ -2618,7 +2618,7 @@ static bool try_async_pf(struct kvm_vcpu *vcpu, gfn_t gfn, gva_t gva,
 
         put_page(pfn_to_page(*pfn));
 
-        if (can_do_async_pf(vcpu)) {
+        if (!no_apf && can_do_async_pf(vcpu)) {
                 trace_kvm_try_async_get_page(async, *pfn);
                 if (kvm_find_async_pf_gfn(vcpu, gfn)) {
                         trace_kvm_async_pf_doublefault(gva, gfn);
@@ -2633,8 +2633,8 @@ static bool try_async_pf(struct kvm_vcpu *vcpu, gfn_t gfn, gva_t gva,
         return false;
 }
 
-static int tdp_page_fault(struct kvm_vcpu *vcpu, gva_t gpa,
-                                u32 error_code)
+static int tdp_page_fault(struct kvm_vcpu *vcpu, gva_t gpa, u32 error_code,
+                          bool no_apf)
 {
         pfn_t pfn;
         int r;
@@ -2656,7 +2656,7 @@ static int tdp_page_fault(struct kvm_vcpu *vcpu, gva_t gpa,
         mmu_seq = vcpu->kvm->mmu_notifier_seq;
         smp_rmb();
 
-        if (try_async_pf(vcpu, gfn, gpa, &pfn))
+        if (try_async_pf(vcpu, no_apf, gfn, gpa, &pfn))
                 return 0;
 
         /* mmio */
@@ -3319,7 +3319,7 @@ int kvm_mmu_page_fault(struct kvm_vcpu *vcpu, gva_t cr2, u32 error_code)
         int r;
         enum emulation_result er;
 
-        r = vcpu->arch.mmu.page_fault(vcpu, cr2, error_code);
+        r = vcpu->arch.mmu.page_fault(vcpu, cr2, error_code, false);
         if (r < 0)
                 goto out;