[Qemu-devel] [PATCH] test for lm capable kernel.

[Glauber Costa]

Don't save x86_64-specific msrs if our kernel does not support them.
Code is already in qemu-kvm.git, but the test function is slightly different.
It follows what the test for msr_start does.

Signed-off-by: Glauber Costa <address@hidden>
---
 target-i386/kvm.c |   37 +++++++++++++++++++++++++++----------
 1 files changed, 27 insertions(+), 10 deletions(-)

diff --git a/target-i386/kvm.c b/target-i386/kvm.c
index 7010999..0e69b57 100644
--- a/target-i386/kvm.c
+++ b/target-i386/kvm.c
@@ -15,6 +15,7 @@
 #include <sys/types.h>
 #include <sys/ioctl.h>
 #include <sys/mman.h>
+#include <sys/utsname.h>
 
 #include <linux/kvm.h>
 
@@ -266,6 +267,20 @@ static int kvm_has_msr_star(CPUState *env)
     return 0;
 }
 
+static int lm_capable_kernel(void)
+{
+    static int lm_capable = -1;
+    struct utsname utsname;
+
+    if (lm_capable != -1) {
+        return lm_capable;
+    }
+
+    uname(&utsname);
+    lm_capable = (strcmp(utsname.machine, "x86_64") == 0);
+    return lm_capable;
+}
+
 int kvm_arch_init(KVMState *s, int smp_cpus)
 {
     int ret;
@@ -478,11 +493,12 @@ static int kvm_put_msrs(CPUState *env)
        kvm_msr_entry_set(&msrs[n++], MSR_STAR, env->star);
     kvm_msr_entry_set(&msrs[n++], MSR_IA32_TSC, env->tsc);
 #ifdef TARGET_X86_64
-    /* FIXME if lm capable */
-    kvm_msr_entry_set(&msrs[n++], MSR_CSTAR, env->cstar);
-    kvm_msr_entry_set(&msrs[n++], MSR_KERNELGSBASE, env->kernelgsbase);
-    kvm_msr_entry_set(&msrs[n++], MSR_FMASK, env->fmask);
-    kvm_msr_entry_set(&msrs[n++], MSR_LSTAR, env->lstar);
+    if (lm_capable_kernel()) {
+        kvm_msr_entry_set(&msrs[n++], MSR_CSTAR, env->cstar);
+        kvm_msr_entry_set(&msrs[n++], MSR_KERNELGSBASE, env->kernelgsbase);
+        kvm_msr_entry_set(&msrs[n++], MSR_FMASK, env->fmask);
+        kvm_msr_entry_set(&msrs[n++], MSR_LSTAR, env->lstar);
+    }
 #endif
     msr_data.info.nmsrs = n;
 
@@ -611,11 +627,12 @@ static int kvm_get_msrs(CPUState *env)
        msrs[n++].index = MSR_STAR;
     msrs[n++].index = MSR_IA32_TSC;
 #ifdef TARGET_X86_64
-    /* FIXME lm_capable_kernel */
-    msrs[n++].index = MSR_CSTAR;
-    msrs[n++].index = MSR_KERNELGSBASE;
-    msrs[n++].index = MSR_FMASK;
-    msrs[n++].index = MSR_LSTAR;
+    if (lm_capable_kernel()) {
+        msrs[n++].index = MSR_CSTAR;
+        msrs[n++].index = MSR_KERNELGSBASE;
+        msrs[n++].index = MSR_FMASK;
+        msrs[n++].index = MSR_LSTAR;
+    }
 #endif
     msr_data.info.nmsrs = n;
     ret = kvm_vcpu_ioctl(env, KVM_GET_MSRS, &msr_data);
-- 
1.6.2.5