The existing -cpu host code simply set every bit inside svm_features
(initializing it to -1), and that makes it impossible to make the
enforce/check options work properly when the user asks for SVM features
explicitly in the command-line.
So, instead of initializing svm_features to -1, use GET_SUPPORTED_CPUID
to fill only the bits that are supported by the host (just like we do
for all other CPUID feature words inside kvm_cpu_fill_host()).
This will keep the existing behavior (as filter_features_for_kvm()
already uses GET_SUPPORTED_CPUID to filter svm_features), but will allow
us to properly check for KVM features inside
kvm_check_features_against_host() later.
For example, we will be able to make this:
$ qemu-system-x86_64 -cpu ...,+pfthreshold,enforce
refuse to start if the SVM "pfthreshold" feature is not supported by the
host (after we fix kvm_check_features_against_host() to check SVM flags
as well).
Signed-off-by: Eduardo Habkost <ehabkost@xxxxxxxxxx>
---
Changes v2:
- Coding style (indentation) fix
Cc: Gleb Natapov <gleb@xxxxxxxxxx>
Cc: Marcelo Tosatti <mtosatti@xxxxxxxxxx>
Cc: Joerg Roedel <joro@xxxxxxxxxx>
Cc: kvm@xxxxxxxxxxxxxxx
---
target-i386/cpu.c | 11 ++++-------
1 file changed, 4 insertions(+), 7 deletions(-)
diff --git a/target-i386/cpu.c b/target-i386/cpu.c
index ec877c7..649cfb2 100644
--- a/target-i386/cpu.c
+++ b/target-i386/cpu.c
@@ -906,13 +906,10 @@ static void kvm_cpu_fill_host(x86_def_t *x86_cpu_def)
}
}
- /*
- * Every SVM feature requires emulation support in KVM - so we can't just
- * read the host features here. KVM might even support SVM features not
- * available on the host hardware. Just set all bits and mask out the
- * unsupported ones later.
- */
- x86_cpu_def->svm_features = -1;
+ /* Other KVM-specific feature fields: */
+ x86_cpu_def->svm_features =
+ kvm_arch_get_supported_cpuid(s, 0x8000000A, 0, R_EDX);
+
#endif /* CONFIG_KVM */
}
--
1.7.11.7
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