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Re: [Qemu-devel] [PATCH 1/2] target-i386: kvm: -cpu host: use GET_SUPPOR
From: |
Igor Mammedov |
Subject: |
Re: [Qemu-devel] [PATCH 1/2] target-i386: kvm: -cpu host: use GET_SUPPORTED_CPUID for SVM features |
Date: |
Wed, 2 Jan 2013 15:33:34 +0100 |
On Fri, 28 Dec 2012 16:37:33 -0200
Eduardo Habkost <address@hidden> wrote:
> 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 <address@hidden>
Reviewed-By: Igor Mammedov <address@hidden>
> ---
> 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 3cd1cee..6e2d32d 100644
> --- a/target-i386/cpu.c
> +++ b/target-i386/cpu.c
> @@ -897,13 +897,10 @@ 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 */
> }
>
- Re: [Qemu-devel] [PATCH 1/2] target-i386: kvm: -cpu host: use GET_SUPPORTED_CPUID for SVM features,
Igor Mammedov <=