[PATCH] KVM: MMU: Detect oom conditions and propagate error to userspace

Signed-off-by: Avi Kivity <avi@qumranet.com>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

4 files changed, 50 insertions, 19 deletions

diff --git a/drivers/kvm/mmu.c b/drivers/kvm/mmu.c
index e96362aa794..7761089ef3b 100644
--- a/drivers/kvm/mmu.c
+++ b/drivers/kvm/mmu.c
@@ -166,19 +166,20 @@ static int is_rmap_pte(u64 pte)
                 == (PT_WRITABLE_MASK | PT_PRESENT_MASK);
 }
 
-static void mmu_topup_memory_cache(struct kvm_mmu_memory_cache *cache,
-                                   size_t objsize, int min)
+static int mmu_topup_memory_cache(struct kvm_mmu_memory_cache *cache,
+                                  size_t objsize, int min)
 {
         void *obj;
 
         if (cache->nobjs >= min)
-                return;
+                return 0;
         while (cache->nobjs < ARRAY_SIZE(cache->objects)) {
                 obj = kzalloc(objsize, GFP_NOWAIT);
                 if (!obj)
-                        BUG();
+                        return -ENOMEM;
                 cache->objects[cache->nobjs++] = obj;
         }
+        return 0;
 }
 
 static void mmu_free_memory_cache(struct kvm_mmu_memory_cache *mc)
@@ -187,12 +188,18 @@ static void mmu_free_memory_cache(struct kvm_mmu_memory_cache *mc)
                 kfree(mc->objects[--mc->nobjs]);
 }
 
-static void mmu_topup_memory_caches(struct kvm_vcpu *vcpu)
+static int mmu_topup_memory_caches(struct kvm_vcpu *vcpu)
 {
-        mmu_topup_memory_cache(&vcpu->mmu_pte_chain_cache,
-                               sizeof(struct kvm_pte_chain), 4);
-        mmu_topup_memory_cache(&vcpu->mmu_rmap_desc_cache,
-                               sizeof(struct kvm_rmap_desc), 1);
+        int r;
+
+        r = mmu_topup_memory_cache(&vcpu->mmu_pte_chain_cache,
+                                   sizeof(struct kvm_pte_chain), 4);
+        if (r)
+                goto out;
+        r = mmu_topup_memory_cache(&vcpu->mmu_rmap_desc_cache,
+                                   sizeof(struct kvm_rmap_desc), 1);
+out:
+        return r;
 }
 
 static void mmu_free_memory_caches(struct kvm_vcpu *vcpu)
@@ -824,8 +831,11 @@ static int nonpaging_page_fault(struct kvm_vcpu *vcpu, gva_t gva,
 {
         gpa_t addr = gva;
         hpa_t paddr;
+        int r;
 
-        mmu_topup_memory_caches(vcpu);
+        r = mmu_topup_memory_caches(vcpu);
+        if (r)
+                return r;
 
         ASSERT(vcpu);
         ASSERT(VALID_PAGE(vcpu->mmu.root_hpa));
@@ -1052,7 +1062,7 @@ int kvm_mmu_reset_context(struct kvm_vcpu *vcpu)
         r = init_kvm_mmu(vcpu);
         if (r < 0)
                 goto out;
-        mmu_topup_memory_caches(vcpu);
+        r = mmu_topup_memory_caches(vcpu);
 out:
         return r;
 }
diff --git a/drivers/kvm/paging_tmpl.h b/drivers/kvm/paging_tmpl.h
index 4e6670ff184..32b38518845 100644
--- a/drivers/kvm/paging_tmpl.h
+++ b/drivers/kvm/paging_tmpl.h
@@ -339,7 +339,8 @@ static int FNAME(fix_write_pf)(struct kvm_vcpu *vcpu,
  *   - normal guest page fault due to the guest pte marked not present, not
  *     writable, or not executable
  *
- *  Returns: 1 if we need to emulate the instruction, 0 otherwise
+ *  Returns: 1 if we need to emulate the instruction, 0 otherwise, or
+ *           a negative value on error.
  */
 static int FNAME(page_fault)(struct kvm_vcpu *vcpu, gva_t addr,
                                u32 error_code)
@@ -351,10 +352,13 @@ static int FNAME(page_fault)(struct kvm_vcpu *vcpu, gva_t addr,
         u64 *shadow_pte;
         int fixed;
         int write_pt = 0;
+        int r;
 
         pgprintk("%s: addr %lx err %x\n", __FUNCTION__, addr, error_code);
 
-        mmu_topup_memory_caches(vcpu);
+        r = mmu_topup_memory_caches(vcpu);
+        if (r)
+                return r;
 
         /*
          * Look up the shadow pte for the faulting address.
diff --git a/drivers/kvm/svm.c b/drivers/kvm/svm.c
index 99250011a47..af1e7b3f917 100644
--- a/drivers/kvm/svm.c
+++ b/drivers/kvm/svm.c
@@ -852,6 +852,7 @@ static int pf_interception(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
         u64 fault_address;
         u32 error_code;
         enum emulation_result er;
+        int r;
 
         if (is_external_interrupt(exit_int_info))
                 push_irq(vcpu, exit_int_info & SVM_EVTINJ_VEC_MASK);
@@ -860,7 +861,12 @@ static int pf_interception(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
 
         fault_address  = vcpu->svm->vmcb->control.exit_info_2;
         error_code = vcpu->svm->vmcb->control.exit_info_1;
-        if (!kvm_mmu_page_fault(vcpu, fault_address, error_code)) {
+        r = kvm_mmu_page_fault(vcpu, fault_address, error_code);
+        if (r < 0) {
+                spin_unlock(&vcpu->kvm->lock);
+                return r;
+        }
+        if (!r) {
                 spin_unlock(&vcpu->kvm->lock);
                 return 1;
         }
@@ -1398,6 +1404,7 @@ static int svm_vcpu_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
         u16 fs_selector;
         u16 gs_selector;
         u16 ldt_selector;
+        int r;
 
 again:
         do_interrupt_requests(vcpu, kvm_run);
@@ -1565,7 +1572,8 @@ again:
                 return 0;
         }
 
-        if (handle_exit(vcpu, kvm_run)) {
+        r = handle_exit(vcpu, kvm_run);
+        if (r > 0) {
                 if (signal_pending(current)) {
                         ++kvm_stat.signal_exits;
                         post_kvm_run_save(vcpu, kvm_run);
@@ -1581,7 +1589,7 @@ again:
                 goto again;
         }
         post_kvm_run_save(vcpu, kvm_run);
-        return 0;
+        return r;
 }
 
 static void svm_flush_tlb(struct kvm_vcpu *vcpu)
diff --git a/drivers/kvm/vmx.c b/drivers/kvm/vmx.c
index 59178ad4d34..ed395673977 100644
--- a/drivers/kvm/vmx.c
+++ b/drivers/kvm/vmx.c
@@ -1289,6 +1289,7 @@ static int handle_exception(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
         unsigned long cr2, rip;
         u32 vect_info;
         enum emulation_result er;
+        int r;
 
         vect_info = vmcs_read32(IDT_VECTORING_INFO_FIELD);
         intr_info = vmcs_read32(VM_EXIT_INTR_INFO);
@@ -1317,7 +1318,12 @@ static int handle_exception(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
                 cr2 = vmcs_readl(EXIT_QUALIFICATION);
 
                 spin_lock(&vcpu->kvm->lock);
-                if (!kvm_mmu_page_fault(vcpu, cr2, error_code)) {
+                r = kvm_mmu_page_fault(vcpu, cr2, error_code);
+                if (r < 0) {
+                        spin_unlock(&vcpu->kvm->lock);
+                        return r;
+                }
+                if (!r) {
                         spin_unlock(&vcpu->kvm->lock);
                         return 1;
                 }
@@ -1680,6 +1686,7 @@ static int vmx_vcpu_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
         u8 fail;
         u16 fs_sel, gs_sel, ldt_sel;
         int fs_gs_ldt_reload_needed;
+        int r;
 
 again:
         /*
@@ -1853,6 +1860,7 @@ again:
         if (fail) {
                 kvm_run->exit_type = KVM_EXIT_TYPE_FAIL_ENTRY;
                 kvm_run->exit_reason = vmcs_read32(VM_INSTRUCTION_ERROR);
+                r = 0;
         } else {
                 if (fs_gs_ldt_reload_needed) {
                         load_ldt(ldt_sel);
@@ -1872,7 +1880,8 @@ again:
                 }
                 vcpu->launched = 1;
                 kvm_run->exit_type = KVM_EXIT_TYPE_VM_EXIT;
-                if (kvm_handle_exit(kvm_run, vcpu)) {
+                r = kvm_handle_exit(kvm_run, vcpu);
+                if (r > 0) {
                         /* Give scheduler a change to reschedule. */
                         if (signal_pending(current)) {
                                 ++kvm_stat.signal_exits;
@@ -1892,7 +1901,7 @@ again:
         }
 
         post_kvm_run_save(vcpu, kvm_run);
-        return 0;
+        return r;
 }
 
 static void vmx_flush_tlb(struct kvm_vcpu *vcpu)