From: Boris Ostrovsky <boris.ostrovsky@xxxxxxx>
In some cases guests should not provide workarounds for errata even when the
physical processor is affected. For example, because of erratum 400 on family
10h processors a Linux guest will read an MSR (resulting in VMEXIT) before
going to idle in order to avoid getting stuck in a non-C0 state. This is not
necessary: HLT and IO instructions are intercepted and therefore there is no
reason for erratum 400 workaround in the guest.
This patch allows us to present a guest with certain errata as fixed,
regardless of the state of actual hardware.
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxx>
Acked-by: Joerg.Roedel <Joerg.Roedel@xxxxxxx>
---
arch/x86/kvm/svm.c | 74 ++++++++++++++++++++++++++++++++++++++++++++++++++++
arch/x86/kvm/x86.c | 2 +-
2 files changed, 75 insertions(+), 1 deletions(-)
diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index e32243e..4bd41b7 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -110,6 +110,13 @@ struct nested_state {
#define MSRPM_OFFSETS 16
static u32 msrpm_offsets[MSRPM_OFFSETS] __read_mostly;
+/*
+ * Set osvw_len to higher value when updated Revision Guides
+ * are published and we know what the new status bits are
+ */
+static uint64_t osvw_len = 4, osvw_status;
+static DEFINE_SPINLOCK(svm_lock);
+
struct vcpu_svm {
struct kvm_vcpu vcpu;
struct vmcb *vmcb;
@@ -556,6 +563,35 @@ static void svm_init_erratum_383(void)
erratum_383_found = true;
}
+
+static int svm_handle_osvw(struct kvm_vcpu *vcpu,
+ uint32_t msr, uint64_t *val)
+{
+ struct kvm_cpuid_entry2 *cpuid_entry;
+
+ /* Guest OSVW support */
+ cpuid_entry = kvm_find_cpuid_entry(vcpu, 0x80000001, 0);
+ if (!cpuid_entry || !(cpuid_entry->ecx & bit(X86_FEATURE_OSVW)))
+ return -1;
+
+ /*
+ * Guests should see errata 400 and 415 as fixed (assuming that
+ * HLT and IO instructions are intercepted).
+ */
+ if (msr == MSR_AMD64_OSVW_ID_LENGTH)
+ *val = (osvw_len >= 3) ? (osvw_len) : 3;
+ else {
+ *val = osvw_status & ~(6ULL);
+
+ if (osvw_len == 0 && boot_cpu_data.x86 == 0x10)
+ /* Mark erratum 298 as present */
+ *val |= 1;
+ }
+
+ return 0;
+}
+
+
static int has_svm(void)
{
const char *msg;
@@ -620,6 +656,37 @@ static int svm_hardware_enable(void *garbage)
__get_cpu_var(current_tsc_ratio) = TSC_RATIO_DEFAULT;
}
+
+ /*
+ * Get OSVW bits.
+ *
+ * Note that it is possible to have a system with mixed processor
+ * revisions and therefore different OSVW bits. If bits are not the same
+ * on different processors then choose the worst case (i.e. if erratum
+ * is present on one processor and not on another then assume that the
+ * erratum is present everywhere).
+ */
+ if (cpu_has(&boot_cpu_data, X86_FEATURE_OSVW)) {
+ uint64_t len, status;
+ int err;
+
+ len = native_read_msr_safe(MSR_AMD64_OSVW_ID_LENGTH, &err);
+ if (!err)
+ status = native_read_msr_safe(MSR_AMD64_OSVW_STATUS,
+ &err);
+
+ spin_lock(&svm_lock);
+ if (err)
+ osvw_status = osvw_len = 0;
+ else {
+ if (len < osvw_len)
+ osvw_len = len;
+ osvw_status |= status;
+ osvw_status &= (1ULL << osvw_len) - 1;
+ }
+ spin_unlock(&svm_lock);
+ }
+
svm_init_erratum_383();
return 0;
@@ -2982,6 +3049,9 @@ static int svm_get_msr(struct kvm_vcpu *vcpu, unsigned ecx, u64 *data)
case MSR_IA32_UCODE_REV:
*data = 0x01000065;
break;
+ case MSR_AMD64_OSVW_ID_LENGTH:
+ case MSR_AMD64_OSVW_STATUS:
+ return svm_handle_osvw(vcpu, ecx, data);
default:
return kvm_get_msr_common(vcpu, ecx, data);
}
@@ -3092,6 +3162,10 @@ static int svm_set_msr(struct kvm_vcpu *vcpu, unsigned ecx, u64 data)
case MSR_VM_IGNNE:
pr_unimpl(vcpu, "unimplemented wrmsr: 0x%x data 0x%llx\n", ecx, data);
break;
+ case MSR_AMD64_OSVW_ID_LENGTH:
+ case MSR_AMD64_OSVW_STATUS:
+ /* Writes are ignored */
+ 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 c38efd7..0a84162 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -2452,7 +2452,7 @@ static void do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function,
const u32 kvm_supported_word6_x86_features =
F(LAHF_LM) | F(CMP_LEGACY) | 0 /*SVM*/ | 0 /* ExtApicSpace */ |
F(CR8_LEGACY) | F(ABM) | F(SSE4A) | F(MISALIGNSSE) |
- F(3DNOWPREFETCH) | 0 /* OSVW */ | 0 /* IBS */ | F(XOP) |
+ F(3DNOWPREFETCH) | F(OSVW) | 0 /* IBS */ | F(XOP) |
0 /* SKINIT, WDT, LWP */ | F(FMA4) | F(TBM);
/* cpuid 0xC0000001.edx */
--
1.7.3.4
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