KVM: propagate fault r/w information to gup(), allow read-only memory

As suggested by Andrea, pass r/w error code to gup(), upgrading read fault
to writable if host pte allows it.

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

1 files changed, 17 insertions, 10 deletions

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 99433943170c..53509f5973db 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -2216,7 +2216,7 @@ static void direct_pte_prefetch(struct kvm_vcpu *vcpu, u64 *sptep)
 }
 
 static int __direct_map(struct kvm_vcpu *vcpu, gpa_t v, int write,
-                        int level, gfn_t gfn, pfn_t pfn)
+                        int map_writable, int level, gfn_t gfn, pfn_t pfn)
 {
         struct kvm_shadow_walk_iterator iterator;
         struct kvm_mmu_page *sp;
@@ -2225,9 +2225,13 @@ static int __direct_map(struct kvm_vcpu *vcpu, gpa_t v, int write,
 
         for_each_shadow_entry(vcpu, (u64)gfn << PAGE_SHIFT, iterator) {
                 if (iterator.level == level) {
-                        mmu_set_spte(vcpu, iterator.sptep, ACC_ALL, ACC_ALL,
+                        unsigned pte_access = ACC_ALL;
+
+                        if (!map_writable)
+                                pte_access &= ~ACC_WRITE_MASK;
+                        mmu_set_spte(vcpu, iterator.sptep, ACC_ALL, pte_access,
                                      0, write, 1, &pt_write,
-                                     level, gfn, pfn, false, true);
+                                     level, gfn, pfn, false, map_writable);
                         direct_pte_prefetch(vcpu, iterator.sptep);
                         ++vcpu->stat.pf_fixed;
                         break;
@@ -2288,6 +2292,7 @@ static int nonpaging_map(struct kvm_vcpu *vcpu, gva_t v, int write, gfn_t gfn)
         int level;
         pfn_t pfn;
         unsigned long mmu_seq;
+        bool map_writable;
 
         level = mapping_level(vcpu, gfn);
 
@@ -2302,7 +2307,7 @@ static int nonpaging_map(struct kvm_vcpu *vcpu, gva_t v, int write, gfn_t gfn)
 
         mmu_seq = vcpu->kvm->mmu_notifier_seq;
         smp_rmb();
-        pfn = gfn_to_pfn(vcpu->kvm, gfn);
+        pfn = gfn_to_pfn_prot(vcpu->kvm, gfn, write, &map_writable);
 
         /* mmio */
         if (is_error_pfn(pfn))
@@ -2312,7 +2317,7 @@ static int nonpaging_map(struct kvm_vcpu *vcpu, gva_t v, int write, gfn_t gfn)
         if (mmu_notifier_retry(vcpu, mmu_seq))
                 goto out_unlock;
         kvm_mmu_free_some_pages(vcpu);
-        r = __direct_map(vcpu, v, write, level, gfn, pfn);
+        r = __direct_map(vcpu, v, write, map_writable, level, gfn, pfn);
         spin_unlock(&vcpu->kvm->mmu_lock);
 
 
@@ -2611,11 +2616,11 @@ static bool can_do_async_pf(struct kvm_vcpu *vcpu)
 }
 
 static bool try_async_pf(struct kvm_vcpu *vcpu, bool no_apf, gfn_t gfn,
-                         gva_t gva, pfn_t *pfn)
+                         gva_t gva, pfn_t *pfn, bool write, bool *writable)
 {
         bool async;
 
-        *pfn = gfn_to_pfn_async(vcpu->kvm, gfn, &async);
+        *pfn = gfn_to_pfn_async(vcpu->kvm, gfn, &async, write, writable);
 
         if (!async)
                 return false; /* *pfn has correct page already */
@@ -2632,7 +2637,7 @@ static bool try_async_pf(struct kvm_vcpu *vcpu, bool no_apf, gfn_t gfn,
                         return true;
         }
 
-        *pfn = gfn_to_pfn(vcpu->kvm, gfn);
+        *pfn = gfn_to_pfn_prot(vcpu->kvm, gfn, write, writable);
 
         return false;
 }
@@ -2645,6 +2650,8 @@ static int tdp_page_fault(struct kvm_vcpu *vcpu, gva_t gpa, u32 error_code,
         int level;
         gfn_t gfn = gpa >> PAGE_SHIFT;
         unsigned long mmu_seq;
+        int write = error_code & PFERR_WRITE_MASK;
+        bool map_writable;
 
         ASSERT(vcpu);
         ASSERT(VALID_PAGE(vcpu->arch.mmu.root_hpa));
@@ -2660,7 +2667,7 @@ static int tdp_page_fault(struct kvm_vcpu *vcpu, gva_t gpa, u32 error_code,
         mmu_seq = vcpu->kvm->mmu_notifier_seq;
         smp_rmb();
 
-        if (try_async_pf(vcpu, no_apf, gfn, gpa, &pfn))
+        if (try_async_pf(vcpu, no_apf, gfn, gpa, &pfn, write, &map_writable))
                 return 0;
 
         /* mmio */
@@ -2670,7 +2677,7 @@ static int tdp_page_fault(struct kvm_vcpu *vcpu, gva_t gpa, u32 error_code,
         if (mmu_notifier_retry(vcpu, mmu_seq))
                 goto out_unlock;
         kvm_mmu_free_some_pages(vcpu);
-        r = __direct_map(vcpu, gpa, error_code & PFERR_WRITE_MASK,
+        r = __direct_map(vcpu, gpa, write, map_writable,
                          level, gfn, pfn);
         spin_unlock(&vcpu->kvm->mmu_lock);