KVM: SVM: Implement workaround for Erratum 383

This patch implements a workaround for AMD erratum 383 into
KVM. Without this erratum fix it is possible for a guest to
kill the host machine. This patch implements the suggested
workaround for hypervisors which will be published by the
next revision guide update.

[jan: fix overflow warning on i386]
[xiao: fix unused variable warning]

Cc: stable@kernel.org
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

2 files changed, 82 insertions, 0 deletions

diff --git a/arch/x86/include/asm/msr-index.h b/arch/x86/include/asm/msr-index.h
index b49d8ca228f6..8c7ae4318629 100644
--- a/arch/x86/include/asm/msr-index.h
+++ b/arch/x86/include/asm/msr-index.h
@@ -110,6 +110,7 @@
 #define MSR_AMD64_PATCH_LOADER          0xc0010020
 #define MSR_AMD64_OSVW_ID_LENGTH        0xc0010140
 #define MSR_AMD64_OSVW_STATUS           0xc0010141
+#define MSR_AMD64_DC_CFG                0xc0011022
 #define MSR_AMD64_IBSFETCHCTL           0xc0011030
 #define MSR_AMD64_IBSFETCHLINAD         0xc0011031
 #define MSR_AMD64_IBSFETCHPHYSAD        0xc0011032
diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 5e1ed033cd7e..ce438e0fdd26 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -28,6 +28,7 @@
 #include <linux/ftrace_event.h>
 #include <linux/slab.h>
 
+#include <asm/tlbflush.h>
 #include <asm/desc.h>
 
 #include <asm/virtext.h>
@@ -56,6 +57,8 @@ MODULE_LICENSE("GPL");
 
 #define DEBUGCTL_RESERVED_BITS (~(0x3fULL))
 
+static bool erratum_383_found __read_mostly;
+
 static const u32 host_save_user_msrs[] = {
 #ifdef CONFIG_X86_64
         MSR_STAR, MSR_LSTAR, MSR_CSTAR, MSR_SYSCALL_MASK, MSR_KERNEL_GS_BASE,
@@ -374,6 +377,31 @@ static void svm_queue_exception(struct kvm_vcpu *vcpu, unsigned nr,
         svm->vmcb->control.event_inj_err = error_code;
 }
 
+static void svm_init_erratum_383(void)
+{
+        u32 low, high;
+        int err;
+        u64 val;
+
+        /* Only Fam10h is affected */
+        if (boot_cpu_data.x86 != 0x10)
+                return;
+
+        /* Use _safe variants to not break nested virtualization */
+        val = native_read_msr_safe(MSR_AMD64_DC_CFG, &err);
+        if (err)
+                return;
+
+        val |= (1ULL << 47);
+
+        low  = lower_32_bits(val);
+        high = upper_32_bits(val);
+
+        native_write_msr_safe(MSR_AMD64_DC_CFG, low, high);
+
+        erratum_383_found = true;
+}
+
 static int has_svm(void)
 {
         const char *msg;
@@ -429,6 +457,8 @@ static int svm_hardware_enable(void *garbage)
 
         wrmsrl(MSR_VM_HSAVE_PA, page_to_pfn(sd->save_area) << PAGE_SHIFT);
 
+        svm_init_erratum_383();
+
         return 0;
 }
 
@@ -1410,8 +1440,59 @@ static int nm_interception(struct vcpu_svm *svm)
         return 1;
 }
 
+static bool is_erratum_383(void)
+{
+        int err, i;
+        u64 value;
+
+        if (!erratum_383_found)
+                return false;
+
+        value = native_read_msr_safe(MSR_IA32_MC0_STATUS, &err);
+        if (err)
+                return false;
+
+        /* Bit 62 may or may not be set for this mce */
+        value &= ~(1ULL << 62);
+
+        if (value != 0xb600000000010015ULL)
+                return false;
+
+        /* Clear MCi_STATUS registers */
+        for (i = 0; i < 6; ++i)
+                native_write_msr_safe(MSR_IA32_MCx_STATUS(i), 0, 0);
+
+        value = native_read_msr_safe(MSR_IA32_MCG_STATUS, &err);
+        if (!err) {
+                u32 low, high;
+
+                value &= ~(1ULL << 2);
+                low    = lower_32_bits(value);
+                high   = upper_32_bits(value);
+
+                native_write_msr_safe(MSR_IA32_MCG_STATUS, low, high);
+        }
+
+        /* Flush tlb to evict multi-match entries */
+        __flush_tlb_all();
+
+        return true;
+}
+
 static void svm_handle_mce(struct vcpu_svm *svm)
 {
+        if (is_erratum_383()) {
+                /*
+                 * Erratum 383 triggered. Guest state is corrupt so kill the
+                 * guest.
+                 */
+                pr_err("KVM: Guest triggered AMD Erratum 383\n");
+
+                set_bit(KVM_REQ_TRIPLE_FAULT, &svm->vcpu.requests);
+
+                return;
+        }
+
         /*
          * On an #MC intercept the MCE handler is not called automatically in
          * the host. So do it by hand here.