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authorMingwei Zhang <mizhang@google.com>2022-04-21 06:14:07 +0300
committerPaolo Bonzini <pbonzini@redhat.com>2022-04-21 22:41:00 +0300
commit683412ccf61294d727ead4a73d97397396e69a6b (patch)
tree2e1f2e5ff4031699ee51b45341590461565f36fc /arch
parentd45829b351ee6ec5f54dd55e6aca1f44fe239fe6 (diff)
downloadlinux-683412ccf61294d727ead4a73d97397396e69a6b.tar.xz
KVM: SEV: add cache flush to solve SEV cache incoherency issues
Flush the CPU caches when memory is reclaimed from an SEV guest (where reclaim also includes it being unmapped from KVM's memslots). Due to lack of coherency for SEV encrypted memory, failure to flush results in silent data corruption if userspace is malicious/broken and doesn't ensure SEV guest memory is properly pinned and unpinned. Cache coherency is not enforced across the VM boundary in SEV (AMD APM vol.2 Section 15.34.7). Confidential cachelines, generated by confidential VM guests have to be explicitly flushed on the host side. If a memory page containing dirty confidential cachelines was released by VM and reallocated to another user, the cachelines may corrupt the new user at a later time. KVM takes a shortcut by assuming all confidential memory remain pinned until the end of VM lifetime. Therefore, KVM does not flush cache at mmu_notifier invalidation events. Because of this incorrect assumption and the lack of cache flushing, malicous userspace can crash the host kernel: creating a malicious VM and continuously allocates/releases unpinned confidential memory pages when the VM is running. Add cache flush operations to mmu_notifier operations to ensure that any physical memory leaving the guest VM get flushed. In particular, hook mmu_notifier_invalidate_range_start and mmu_notifier_release events and flush cache accordingly. The hook after releasing the mmu lock to avoid contention with other vCPUs. Cc: stable@vger.kernel.org Suggested-by: Sean Christpherson <seanjc@google.com> Reported-by: Mingwei Zhang <mizhang@google.com> Signed-off-by: Mingwei Zhang <mizhang@google.com> Message-Id: <20220421031407.2516575-4-mizhang@google.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'arch')
-rw-r--r--arch/x86/include/asm/kvm-x86-ops.h1
-rw-r--r--arch/x86/include/asm/kvm_host.h1
-rw-r--r--arch/x86/kvm/svm/sev.c8
-rw-r--r--arch/x86/kvm/svm/svm.c1
-rw-r--r--arch/x86/kvm/svm/svm.h2
-rw-r--r--arch/x86/kvm/x86.c5
6 files changed, 18 insertions, 0 deletions
diff --git a/arch/x86/include/asm/kvm-x86-ops.h b/arch/x86/include/asm/kvm-x86-ops.h
index 3c368b639c04..1a6d7e3f6c32 100644
--- a/arch/x86/include/asm/kvm-x86-ops.h
+++ b/arch/x86/include/asm/kvm-x86-ops.h
@@ -118,6 +118,7 @@ KVM_X86_OP_OPTIONAL(mem_enc_register_region)
KVM_X86_OP_OPTIONAL(mem_enc_unregister_region)
KVM_X86_OP_OPTIONAL(vm_copy_enc_context_from)
KVM_X86_OP_OPTIONAL(vm_move_enc_context_from)
+KVM_X86_OP_OPTIONAL(guest_memory_reclaimed)
KVM_X86_OP(get_msr_feature)
KVM_X86_OP(can_emulate_instruction)
KVM_X86_OP(apic_init_signal_blocked)
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index e0c0f0e1f754..4ff36610af6a 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1484,6 +1484,7 @@ struct kvm_x86_ops {
int (*mem_enc_unregister_region)(struct kvm *kvm, struct kvm_enc_region *argp);
int (*vm_copy_enc_context_from)(struct kvm *kvm, unsigned int source_fd);
int (*vm_move_enc_context_from)(struct kvm *kvm, unsigned int source_fd);
+ void (*guest_memory_reclaimed)(struct kvm *kvm);
int (*get_msr_feature)(struct kvm_msr_entry *entry);
diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index 9a0375987029..0ad70c12c7c3 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -2262,6 +2262,14 @@ do_wbinvd:
wbinvd_on_all_cpus();
}
+void sev_guest_memory_reclaimed(struct kvm *kvm)
+{
+ if (!sev_guest(kvm))
+ return;
+
+ wbinvd_on_all_cpus();
+}
+
void sev_free_vcpu(struct kvm_vcpu *vcpu)
{
struct vcpu_svm *svm;
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index bd4c64b362d2..7e45d03cd018 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -4620,6 +4620,7 @@ static struct kvm_x86_ops svm_x86_ops __initdata = {
.mem_enc_ioctl = sev_mem_enc_ioctl,
.mem_enc_register_region = sev_mem_enc_register_region,
.mem_enc_unregister_region = sev_mem_enc_unregister_region,
+ .guest_memory_reclaimed = sev_guest_memory_reclaimed,
.vm_copy_enc_context_from = sev_vm_copy_enc_context_from,
.vm_move_enc_context_from = sev_vm_move_enc_context_from,
diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h
index f77a7d2d39dd..f76deff71002 100644
--- a/arch/x86/kvm/svm/svm.h
+++ b/arch/x86/kvm/svm/svm.h
@@ -609,6 +609,8 @@ int sev_mem_enc_unregister_region(struct kvm *kvm,
struct kvm_enc_region *range);
int sev_vm_copy_enc_context_from(struct kvm *kvm, unsigned int source_fd);
int sev_vm_move_enc_context_from(struct kvm *kvm, unsigned int source_fd);
+void sev_guest_memory_reclaimed(struct kvm *kvm);
+
void pre_sev_run(struct vcpu_svm *svm, int cpu);
void __init sev_set_cpu_caps(void);
void __init sev_hardware_setup(void);
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index c89dc09a764f..a6ab19afc638 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -9889,6 +9889,11 @@ void kvm_arch_mmu_notifier_invalidate_range(struct kvm *kvm,
kvm_make_all_cpus_request(kvm, KVM_REQ_APIC_PAGE_RELOAD);
}
+void kvm_arch_guest_memory_reclaimed(struct kvm *kvm)
+{
+ static_call_cond(kvm_x86_guest_memory_reclaimed)(kvm);
+}
+
static void kvm_vcpu_reload_apic_access_page(struct kvm_vcpu *vcpu)
{
if (!lapic_in_kernel(vcpu))