KVM: Cache pdptrs

Instead of reloading the pdptrs on every entry and exit (vmcs writes on vmx,
guest memory access on svm) extract them on demand.

Signed-off-by: Avi Kivity <avi@redhat.com>

7 files changed, 63 insertions, 13 deletions

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 81c68f630b14..1cc901ec4ba5 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -120,6 +120,10 @@ enum kvm_reg {
         NR_VCPU_REGS
 };
 
+enum kvm_reg_ex {
+        VCPU_EXREG_PDPTR = NR_VCPU_REGS,
+};
+
 enum {
         VCPU_SREG_ES,
         VCPU_SREG_CS,
diff --git a/arch/x86/kvm/kvm_cache_regs.h b/arch/x86/kvm/kvm_cache_regs.h
index 1ff819dce7d3..7bcc5b6a4403 100644
--- a/arch/x86/kvm/kvm_cache_regs.h
+++ b/arch/x86/kvm/kvm_cache_regs.h
@@ -29,4 +29,13 @@ static inline void kvm_rip_write(struct kvm_vcpu *vcpu, unsigned long val)
         kvm_register_write(vcpu, VCPU_REGS_RIP, val);
 }
 
+static inline u64 kvm_pdptr_read(struct kvm_vcpu *vcpu, int index)
+{
+        if (!test_bit(VCPU_EXREG_PDPTR,
+                      (unsigned long *)&vcpu->arch.regs_avail))
+                kvm_x86_ops->cache_reg(vcpu, VCPU_EXREG_PDPTR);
+
+        return vcpu->arch.pdptrs[index];
+}
+
 #endif
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 0ef5bb2b4043..8ee67e3fb9d0 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -18,6 +18,7 @@
  */
 
 #include "mmu.h"
+#include "kvm_cache_regs.h"
 
 #include <linux/kvm_host.h>
 #include <linux/types.h>
@@ -1954,6 +1955,7 @@ static int mmu_alloc_roots(struct kvm_vcpu *vcpu)
         gfn_t root_gfn;
         struct kvm_mmu_page *sp;
         int direct = 0;
+        u64 pdptr;
 
         root_gfn = vcpu->arch.cr3 >> PAGE_SHIFT;
 
@@ -1981,11 +1983,12 @@ static int mmu_alloc_roots(struct kvm_vcpu *vcpu)
 
                 ASSERT(!VALID_PAGE(root));
                 if (vcpu->arch.mmu.root_level == PT32E_ROOT_LEVEL) {
-                        if (!is_present_pte(vcpu->arch.pdptrs[i])) {
+                        pdptr = kvm_pdptr_read(vcpu, i);
+                        if (!is_present_pte(pdptr)) {
                                 vcpu->arch.mmu.pae_root[i] = 0;
                                 continue;
                         }
-                        root_gfn = vcpu->arch.pdptrs[i] >> PAGE_SHIFT;
+                        root_gfn = pdptr >> PAGE_SHIFT;
                 } else if (vcpu->arch.mmu.root_level == 0)
                         root_gfn = 0;
                 if (mmu_check_root(vcpu, root_gfn))
diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h
index 67785f635399..4cb1dbfd7c2a 100644
--- a/arch/x86/kvm/paging_tmpl.h
+++ b/arch/x86/kvm/paging_tmpl.h
@@ -131,7 +131,7 @@ walk:
         pte = vcpu->arch.cr3;
 #if PTTYPE == 64
         if (!is_long_mode(vcpu)) {
-                pte = vcpu->arch.pdptrs[(addr >> 30) & 3];
+                pte = kvm_pdptr_read(vcpu, (addr >> 30) & 3);
                 if (!is_present_pte(pte))
                         goto not_present;
                 --walker->level;
diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 522e69597a16..7749b0692cb2 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -777,6 +777,18 @@ static void svm_set_rflags(struct kvm_vcpu *vcpu, unsigned long rflags)
         to_svm(vcpu)->vmcb->save.rflags = rflags;
 }
 
+static void svm_cache_reg(struct kvm_vcpu *vcpu, enum kvm_reg reg)
+{
+        switch (reg) {
+        case VCPU_EXREG_PDPTR:
+                BUG_ON(!npt_enabled);
+                load_pdptrs(vcpu, vcpu->arch.cr3);
+                break;
+        default:
+                BUG();
+        }
+}
+
 static void svm_set_vintr(struct vcpu_svm *svm)
 {
         svm->vmcb->control.intercept |= 1ULL << INTERCEPT_VINTR;
@@ -2285,12 +2297,6 @@ static int handle_exit(struct kvm_run *kvm_run, struct kvm_vcpu *vcpu)
                 }
                 vcpu->arch.cr0 = svm->vmcb->save.cr0;
                 vcpu->arch.cr3 = svm->vmcb->save.cr3;
-                if (is_paging(vcpu) && is_pae(vcpu) && !is_long_mode(vcpu)) {
-                        if (!load_pdptrs(vcpu, vcpu->arch.cr3)) {
-                                kvm_inject_gp(vcpu, 0);
-                                return 1;
-                        }
-                }
                 if (mmu_reload) {
                         kvm_mmu_reset_context(vcpu);
                         kvm_mmu_load(vcpu);
@@ -2641,6 +2647,11 @@ static void svm_vcpu_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
 
         svm->next_rip = 0;
 
+        if (npt_enabled) {
+                vcpu->arch.regs_avail &= ~(1 << VCPU_EXREG_PDPTR);
+                vcpu->arch.regs_dirty &= ~(1 << VCPU_EXREG_PDPTR);
+        }
+
         svm_complete_interrupts(svm);
 }
 
@@ -2749,6 +2760,7 @@ static struct kvm_x86_ops svm_x86_ops = {
         .set_gdt = svm_set_gdt,
         .get_dr = svm_get_dr,
         .set_dr = svm_set_dr,
+        .cache_reg = svm_cache_reg,
         .get_rflags = svm_get_rflags,
         .set_rflags = svm_set_rflags,
 
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 752465f98bfd..d726dec69529 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -161,6 +161,8 @@ static struct kvm_vmx_segment_field {
         VMX_SEGMENT_FIELD(LDTR),
 };
 
+static void ept_save_pdptrs(struct kvm_vcpu *vcpu);
+
 /*
  * Keep MSR_K6_STAR at the end, as setup_msrs() will try to optimize it
  * away by decrementing the array size.
@@ -1047,6 +1049,10 @@ static void vmx_cache_reg(struct kvm_vcpu *vcpu, enum kvm_reg reg)
         case VCPU_REGS_RIP:
                 vcpu->arch.regs[VCPU_REGS_RIP] = vmcs_readl(GUEST_RIP);
                 break;
+        case VCPU_EXREG_PDPTR:
+                if (enable_ept)
+                        ept_save_pdptrs(vcpu);
+                break;
         default:
                 break;
         }
@@ -1546,6 +1552,10 @@ static void vmx_decache_cr4_guest_bits(struct kvm_vcpu *vcpu)
 
 static void ept_load_pdptrs(struct kvm_vcpu *vcpu)
 {
+        if (!test_bit(VCPU_EXREG_PDPTR,
+                      (unsigned long *)&vcpu->arch.regs_dirty))
+                return;
+
         if (is_paging(vcpu) && is_pae(vcpu) && !is_long_mode(vcpu)) {
                 vmcs_write64(GUEST_PDPTR0, vcpu->arch.pdptrs[0]);
                 vmcs_write64(GUEST_PDPTR1, vcpu->arch.pdptrs[1]);
@@ -1562,6 +1572,11 @@ static void ept_save_pdptrs(struct kvm_vcpu *vcpu)
                 vcpu->arch.pdptrs[2] = vmcs_read64(GUEST_PDPTR2);
                 vcpu->arch.pdptrs[3] = vmcs_read64(GUEST_PDPTR3);
         }
+
+        __set_bit(VCPU_EXREG_PDPTR,
+                  (unsigned long *)&vcpu->arch.regs_avail);
+        __set_bit(VCPU_EXREG_PDPTR,
+                  (unsigned long *)&vcpu->arch.regs_dirty);
 }
 
 static void vmx_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4);
@@ -3255,10 +3270,8 @@ static int vmx_handle_exit(struct kvm_run *kvm_run, struct kvm_vcpu *vcpu)
 
         /* Access CR3 don't cause VMExit in paging mode, so we need
          * to sync with guest real CR3. */
-        if (enable_ept && is_paging(vcpu)) {
+        if (enable_ept && is_paging(vcpu))
                 vcpu->arch.cr3 = vmcs_readl(GUEST_CR3);
-                ept_save_pdptrs(vcpu);
-        }
 
         if (unlikely(vmx->fail)) {
                 kvm_run->exit_reason = KVM_EXIT_FAIL_ENTRY;
@@ -3567,7 +3580,8 @@ static void vmx_vcpu_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
 #endif
               );
 
-        vcpu->arch.regs_avail = ~((1 << VCPU_REGS_RIP) | (1 << VCPU_REGS_RSP));
+        vcpu->arch.regs_avail = ~((1 << VCPU_REGS_RIP) | (1 << VCPU_REGS_RSP)
+                                  | (1 << VCPU_EXREG_PDPTR));
         vcpu->arch.regs_dirty = 0;
 
         get_debugreg(vcpu->arch.dr6, 6);
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 75e9df097845..2ad8c97f58cc 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -246,6 +246,10 @@ int load_pdptrs(struct kvm_vcpu *vcpu, unsigned long cr3)
         ret = 1;
 
         memcpy(vcpu->arch.pdptrs, pdpte, sizeof(vcpu->arch.pdptrs));
+        __set_bit(VCPU_EXREG_PDPTR,
+                  (unsigned long *)&vcpu->arch.regs_avail);
+        __set_bit(VCPU_EXREG_PDPTR,
+                  (unsigned long *)&vcpu->arch.regs_dirty);
 out:
 
         return ret;
@@ -261,6 +265,10 @@ static bool pdptrs_changed(struct kvm_vcpu *vcpu)
         if (is_long_mode(vcpu) || !is_pae(vcpu))
                 return false;
 
+        if (!test_bit(VCPU_EXREG_PDPTR,
+                      (unsigned long *)&vcpu->arch.regs_avail))
+                return true;
+
         r = kvm_read_guest(vcpu->kvm, vcpu->arch.cr3 & ~31u, pdpte, sizeof(pdpte));
         if (r < 0)
                 goto out;