[PATCH] qemu-kvm: preserve the hypervisor bit while KVM trims the CPUID bits

[PATCH] qemu-kvm: preserve the hypervisor bit while KVM trims the CPUID bits

[Andre Przywara]

The KVM kernel will disable all bits in CPUID which are not present in
the host. As this is mostly true for the hypervisor bit (1.ecx),
preserve its value before the trim and restore it afterwards.
This is similar to commit 6c0d7ee8, but since qemu-kvm uses another code
path it has to be inserted in qemu-kvm-x86.c, too.

Signed-off-by: Andre Przywara <andre.przywara@amd.com>
---
 qemu-kvm-x86.c |    5 +++++
 1 files changed, 5 insertions(+), 0 deletions(-)

diff --git a/qemu-kvm-x86.c b/qemu-kvm-x86.c
index d6735c1..b02e604 100644
--- a/qemu-kvm-x86.c
+++ b/qemu-kvm-x86.c
@@ -1211,8 +1211,13 @@ int kvm_arch_qemu_init_env(CPUState *cenv)
 
     kvm_trim_features(&cenv->cpuid_features,
                       kvm_arch_get_supported_cpuid(cenv, 1, R_EDX));
+
+    /* prevent the hypervisor bit from being cleared by the kernel */
+    i = env->cpuid_ext_features & CPUID_EXT_HYPERVISOR;
     kvm_trim_features(&cenv->cpuid_ext_features,
                       kvm_arch_get_supported_cpuid(cenv, 1, R_ECX));
+    env->cpuid_ext_features |= i;
+
     kvm_trim_features(&cenv->cpuid_ext2_features,
                       kvm_arch_get_supported_cpuid(cenv, 0x80000001, R_EDX));
     kvm_trim_features(&cenv->cpuid_ext3_features,
-- 
1.6.1.3

[PATCH v2] qemu-kvm: preserve the hypervisor bit while KVM trims the CPUID bits

[Andre Przywara]

The KVM kernel will disable all bits in CPUID which are not present in
the host. As this is mostly true for the hypervisor bit (1.ecx),
preserve its value before the trim and restore it afterwards.
This is similar to commit 6c0d7ee8, but since qemu-kvm uses another code
path it has to be inserted in qemu-kvm-x86.c, too.

Signed-off-by: Andre Przywara <andre.przywara@amd.com>
---
 qemu-kvm-x86.c |    5 +++++
 1 files changed, 5 insertions(+), 0 deletions(-)

The last patch had a typo (and I compile tested the wrong branch), so
here is the correct version.

Regards,
Andre.

diff --git a/qemu-kvm-x86.c b/qemu-kvm-x86.c
index d6735c1..7505380 100644
--- a/qemu-kvm-x86.c
+++ b/qemu-kvm-x86.c
@@ -1211,8 +1211,13 @@ int kvm_arch_qemu_init_env(CPUState *cenv)
 
     kvm_trim_features(&cenv->cpuid_features,
                       kvm_arch_get_supported_cpuid(cenv, 1, R_EDX));
+
+    /* prevent the hypervisor bit from being cleared by the kernel */
+    i = cenv->cpuid_ext_features & CPUID_EXT_HYPERVISOR;
     kvm_trim_features(&cenv->cpuid_ext_features,
                       kvm_arch_get_supported_cpuid(cenv, 1, R_ECX));
+    cenv->cpuid_ext_features |= i;
+
     kvm_trim_features(&cenv->cpuid_ext2_features,
                       kvm_arch_get_supported_cpuid(cenv, 0x80000001, R_EDX));
     kvm_trim_features(&cenv->cpuid_ext3_features,
-- 
1.6.1.3

Re: [PATCH v2] qemu-kvm: preserve the hypervisor bit while KVM trims the CPUID bits

[Avi Kivity]

On 07/02/2009 05:45 PM, Andre Przywara wrote:
> The KVM kernel will disable all bits in CPUID which are not present in
> the host. As this is mostly true for the hypervisor bit (1.ecx),
> preserve its value before the trim and restore it afterwards.
> This is similar to commit 6c0d7ee8, but since qemu-kvm uses another code
> path it has to be inserted in qemu-kvm-x86.c, too.
>    

Applied, thanks.

-- 
error compiling committee.c: too many arguments to function