[Qemu-devel] [PATCH for-2.9 v3 2/3] i386/kvm: Blacklist TSX on known broken hosts

[Eduardo Habkost]

Some Intel CPUs are known to have a broken TSX implementation. A
microcode update from Intel disabled TSX on those CPUs, but
GET_SUPPORTED_CPUID might be reporting it as supported if the
hosts were not updated yet.

Manually fixup the GET_SUPPORTED_CPUID data to ensure we will
never enable TSX when running on those hosts.

Reference:
* glibc commit 2702856bf45c82cf8e69f2064f5aa15c0ceb6359:
  
https://sourceware.org/git/?p=glibc.git;a=commit;h=2702856bf45c82cf8e69f2064f5aa15c0ceb6359

Signed-off-by: Eduardo Habkost <address@hidden>
---
 target/i386/kvm.c | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/target/i386/kvm.c b/target/i386/kvm.c
index 887a81268f..472399fb2c 100644
--- a/target/i386/kvm.c
+++ b/target/i386/kvm.c
@@ -266,6 +266,19 @@ static int get_para_features(KVMState *s)
     return features;
 }
 
+static bool host_tsx_blacklisted(void)
+{
+    int family, model, stepping;\
+    char vendor[CPUID_VENDOR_SZ + 1];
+
+    host_vendor_fms(vendor, &family, &model, &stepping);
+
+    /* Check if we are running on a Haswell host known to have broken TSX */
+    return !strcmp(vendor, CPUID_VENDOR_INTEL) &&
+           (family == 6) &&
+           ((model == 63 && stepping < 4) ||
+            model == 60 || model == 69 || model == 70);
+}
 
 /* Returns the value for a specific register on the cpuid entry
  */
@@ -349,6 +362,10 @@ uint32_t kvm_arch_get_supported_cpuid(KVMState *s, 
uint32_t function,
         }
     } else if (function == 6 && reg == R_EAX) {
         ret |= CPUID_6_EAX_ARAT; /* safe to allow because of emulated APIC */
+    } else if (function == 7 && index == 0 && reg == R_EBX) {
+        if (host_tsx_blacklisted()) {
+            ret &= ~(CPUID_7_0_EBX_RTM | CPUID_7_0_EBX_HLE);
+        }
     } else if (function == 0x80000001 && reg == R_EDX) {
         /* On Intel, kvm returns cpuid according to the Intel spec,
          * so add missing bits according to the AMD spec:
-- 
2.11.0.259.g40922b1