From: Paolo Bonzini <pbonzini@redhat.com>
Date: Tue, 30 Jun 2020 13:49:27 +0000 (-0400)
Subject: KVM: x86: believe what KVM says about WAITPKG
X-Git-Tag: qemu-xen-4.14.1^2~57
X-Git-Url: http://xenbits.xensource.com/gitweb?a=commitdiff_plain;h=458ae56d22a78d84135fd5dfe8e837be83d74ce9;p=qemu-xen.git

KVM: x86: believe what KVM says about WAITPKG

Currently, QEMU is overriding KVM_GET_SUPPORTED_CPUID's answer for
the WAITPKG bit depending on the "-overcommit cpu-pm" setting.  This is a
bad idea because it does not even check if the host supports it, but it
can be done in x86_cpu_realizefn just like we do for the MONITOR bit.

This patch moves it there, while making it conditional on host
support for the related UMWAIT MSR.

Cc: qemu-stable@nongnu.org
Reported-by: Maxim Levitsky <mlevitsk@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
(cherry picked from commit e1e43813e7908b063938a3d01f172f88f6190c80)
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>
---

diff --git a/target/i386/cpu.c b/target/i386/cpu.c
index 90ffc5f3b1..471db0724f 100644
--- a/target/i386/cpu.c
+++ b/target/i386/cpu.c
@@ -6491,6 +6491,9 @@ static void x86_cpu_realizefn(DeviceState *dev, Error **errp)
             host_cpuid(5, 0, &cpu->mwait.eax, &cpu->mwait.ebx,
                        &cpu->mwait.ecx, &cpu->mwait.edx);
             env->features[FEAT_1_ECX] |= CPUID_EXT_MONITOR;
+            if (kvm_enabled() && kvm_has_waitpkg()) {
+                env->features[FEAT_7_0_ECX] |= CPUID_7_0_ECX_WAITPKG;
+            }
         }
         if (kvm_enabled() && cpu->ucode_rev == 0) {
             cpu->ucode_rev = kvm_arch_get_supported_msr_feature(kvm_state,
diff --git a/target/i386/kvm.c b/target/i386/kvm.c
index 4901c6dd74..f9c873bcad 100644
--- a/target/i386/kvm.c
+++ b/target/i386/kvm.c
@@ -407,12 +407,6 @@ uint32_t kvm_arch_get_supported_cpuid(KVMState *s, uint32_t function,
         if (host_tsx_blacklisted()) {
             ret &= ~(CPUID_7_0_EBX_RTM | CPUID_7_0_EBX_HLE);
         }
-    } else if (function == 7 && index == 0 && reg == R_ECX) {
-        if (enable_cpu_pm) {
-            ret |= CPUID_7_0_ECX_WAITPKG;
-        } else {
-            ret &= ~CPUID_7_0_ECX_WAITPKG;
-        }
     } else if (function == 7 && index == 0 && reg == R_EDX) {
         /*
          * Linux v4.17-v4.20 incorrectly return ARCH_CAPABILITIES on SVM hosts.
@@ -4678,3 +4672,8 @@ int kvm_arch_msi_data_to_gsi(uint32_t data)
 {
     abort();
 }
+
+bool kvm_has_waitpkg(void)
+{
+    return has_msr_umwait;
+}
diff --git a/target/i386/kvm_i386.h b/target/i386/kvm_i386.h
index 00bde7acaf..064b8798a2 100644
--- a/target/i386/kvm_i386.h
+++ b/target/i386/kvm_i386.h
@@ -44,6 +44,7 @@ void kvm_put_apicbase(X86CPU *cpu, uint64_t value);
 
 bool kvm_enable_x2apic(void);
 bool kvm_has_x2apic_api(void);
+bool kvm_has_waitpkg(void);
 
 bool kvm_hv_vpindex_settable(void);