KVM: SVM: Implement hsave

Implement the hsave MSR, that gives the VCPU a GPA to save the
old guest state in.

v2 allows userspace to save/restore hsave
v4 dummys out the hsave MSR, so we use a host page
v6 remembers the guest's hsave and exports the MSR

Acked-by: Joerg Roedel <joro@8bytes.org>
Signed-off-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Avi Kivity <avi@redhat.com>

3 files changed, 16 insertions, 1 deletions

diff --git a/arch/x86/kvm/kvm_svm.h b/arch/x86/kvm/kvm_svm.h
index 8e5ee99551f6..a0877cac7b9c 100644
--- a/arch/x86/kvm/kvm_svm.h
+++ b/arch/x86/kvm/kvm_svm.h
@@ -41,6 +41,8 @@ struct vcpu_svm {
         unsigned long host_dr7;
 
         u32 *msrpm;
+        struct vmcb *hsave;
+        u64 hsave_msr;
 };
 
 #endif
diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 79cc06bfe57c..59aaff1c9597 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -626,6 +626,7 @@ static struct kvm_vcpu *svm_create_vcpu(struct kvm *kvm, unsigned int id)
         struct vcpu_svm *svm;
         struct page *page;
         struct page *msrpm_pages;
+        struct page *hsave_page;
         int err;
 
         svm = kmem_cache_zalloc(kvm_vcpu_cache, GFP_KERNEL);
@@ -651,6 +652,11 @@ static struct kvm_vcpu *svm_create_vcpu(struct kvm *kvm, unsigned int id)
         svm->msrpm = page_address(msrpm_pages);
         svm_vcpu_init_msrpm(svm->msrpm);
 
+        hsave_page = alloc_page(GFP_KERNEL);
+        if (!hsave_page)
+                goto uninit;
+        svm->hsave = page_address(hsave_page);
+
         svm->vmcb = page_address(page);
         clear_page(svm->vmcb);
         svm->vmcb_pa = page_to_pfn(page) << PAGE_SHIFT;
@@ -680,6 +686,7 @@ static void svm_free_vcpu(struct kvm_vcpu *vcpu)
 
         __free_page(pfn_to_page(svm->vmcb_pa >> PAGE_SHIFT));
         __free_pages(virt_to_page(svm->msrpm), MSRPM_ALLOC_ORDER);
+        __free_page(virt_to_page(svm->hsave));
         kvm_vcpu_uninit(vcpu);
         kmem_cache_free(kvm_vcpu_cache, svm);
 }
@@ -1377,6 +1384,9 @@ static int svm_get_msr(struct kvm_vcpu *vcpu, unsigned ecx, u64 *data)
         case MSR_IA32_LASTINTTOIP:
                 *data = svm->vmcb->save.last_excp_to;
                 break;
+        case MSR_VM_HSAVE_PA:
+                *data = svm->hsave_msr;
+                break;
         default:
                 return kvm_get_msr_common(vcpu, ecx, data);
         }
@@ -1471,6 +1481,9 @@ static int svm_set_msr(struct kvm_vcpu *vcpu, unsigned ecx, u64 data)
                 pr_unimpl(vcpu, "unimplemented perfctr wrmsr: 0x%x data 0x%llx\n", ecx, data);
 
                 break;
+        case MSR_VM_HSAVE_PA:
+                svm->hsave_msr = data;
+                break;
         default:
                 return kvm_set_msr_common(vcpu, ecx, data);
         }
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 758b7a155ae9..99165a961f08 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -456,7 +456,7 @@ static u32 msrs_to_save[] = {
         MSR_CSTAR, MSR_KERNEL_GS_BASE, MSR_SYSCALL_MASK, MSR_LSTAR,
 #endif
         MSR_IA32_TIME_STAMP_COUNTER, MSR_KVM_SYSTEM_TIME, MSR_KVM_WALL_CLOCK,
-        MSR_IA32_PERF_STATUS, MSR_IA32_CR_PAT
+        MSR_IA32_PERF_STATUS, MSR_IA32_CR_PAT, MSR_VM_HSAVE_PA
 };
 
 static unsigned num_msrs_to_save;