target/i386: Advertise MWAIT iff host supports
host_cpu_realizefn() sets CPUID_EXT_MONITOR without consulting host/KVM
capabilities. This may cause problems:
- If MWAIT/MONITOR is not available on the host, advertising this
feature to the guest and executing MWAIT/MONITOR from the guest
triggers #UD and the guest doesn't boot. This is because typically
#UD takes priority over VM-Exit interception checks and KVM doesn't
emulate MONITOR/MWAIT on #UD.
- If KVM doesn't support KVM_X86_DISABLE_EXITS_MWAIT, MWAIT/MONITOR
from the guest are intercepted by KVM, which is not what cpu-pm=on
intends to do.
In these cases, MWAIT/MONITOR should not be exposed to the guest.
The logic in kvm_arch_get_supported_cpuid() to handle CPUID_EXT_MONITOR
is correct and sufficient, and we can't set CPUID_EXT_MONITOR after
x86_cpu_filter_features().
This was not an issue before commit 662175b91ff ("i386: reorder call to
cpu_exec_realizefn") because the feature added in the accel-specific
realizefn could be checked against host availability and filtered out.
Additionally, it seems not a good idea to handle guest CPUID leaves in
host_cpu_realizefn(), and this patch merges host_cpu_enable_cpu_pm()
into kvm_cpu_realizefn().
Fixes: f5cc5a5c1686 ("i386: split cpu accelerators from cpu.c, using AccelCPUClass")
Fixes: 662175b91ff2 ("i386: reorder call to cpu_exec_realizefn")
Signed-off-by: Zide Chen <zide.chen@intel.com>
Reviewed-by: Zhao Liu <zhao1.liu@intel.com>
Reviewed-by: Xiaoyao Li <xiaoyao.li@intel.com>
Reviewed-by: Igor Mammedov <imammedo@redhat.com>
Reviewed-by: Michael Tokarev <mjt@tls.msk.ru>
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
diff --git a/target/i386/host-cpu.c b/target/i386/host-cpu.c
index 280e427..8b8bf5a 100644
--- a/target/i386/host-cpu.c
+++ b/target/i386/host-cpu.c
@@ -42,15 +42,6 @@
return host_phys_bits;
}
-static void host_cpu_enable_cpu_pm(X86CPU *cpu)
-{
- CPUX86State *env = &cpu->env;
-
- host_cpuid(5, 0, &cpu->mwait.eax, &cpu->mwait.ebx,
- &cpu->mwait.ecx, &cpu->mwait.edx);
- env->features[FEAT_1_ECX] |= CPUID_EXT_MONITOR;
-}
-
static uint32_t host_cpu_adjust_phys_bits(X86CPU *cpu)
{
uint32_t host_phys_bits = host_cpu_phys_bits();
@@ -83,9 +74,6 @@
X86CPU *cpu = X86_CPU(cs);
CPUX86State *env = &cpu->env;
- if (cpu->max_features && enable_cpu_pm) {
- host_cpu_enable_cpu_pm(cpu);
- }
if (env->features[FEAT_8000_0001_EDX] & CPUID_EXT2_LM) {
uint32_t phys_bits = host_cpu_adjust_phys_bits(cpu);
diff --git a/target/i386/kvm/kvm-cpu.c b/target/i386/kvm/kvm-cpu.c
index f9b99b5..d57a68a 100644
--- a/target/i386/kvm/kvm-cpu.c
+++ b/target/i386/kvm/kvm-cpu.c
@@ -64,8 +64,15 @@
* cpu_common_realizefn() (via xcc->parent_realize)
*/
if (cpu->max_features) {
- if (enable_cpu_pm && kvm_has_waitpkg()) {
- env->features[FEAT_7_0_ECX] |= CPUID_7_0_ECX_WAITPKG;
+ if (enable_cpu_pm) {
+ if (kvm_has_waitpkg()) {
+ env->features[FEAT_7_0_ECX] |= CPUID_7_0_ECX_WAITPKG;
+ }
+
+ if (env->features[FEAT_1_ECX] & CPUID_EXT_MONITOR) {
+ host_cpuid(5, 0, &cpu->mwait.eax, &cpu->mwait.ebx,
+ &cpu->mwait.ecx, &cpu->mwait.edx);
+ }
}
if (cpu->ucode_rev == 0) {
cpu->ucode_rev =
