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SubjectRe: [PATCH 05/47] KVM: VMX: Optimize vmx_get_cpl()
On 08/26/2009 05:15 PM, Roel Kluin wrote:
> Op 26-08-09 12:29, Avi Kivity schreef:
>
>> Instead of calling vmx_get_segment() (which reads a whole bunch of
>> vmcs fields), read only the cs selector which contains the cpl.
>>
>> Signed-off-by: Avi Kivity<avi@redhat.com>
>>
> Can't we also optimise cs_ss_rpl_check()? (Please review, untested.)
>
> ------------->8 ---------------------- 8< --------------------
> Instead of calling vmx_get_segment() (which reads a whole bunch of
> vmcs fields), read only the cs/ss selectors which contains the rpls.
>
>

It's really a slowpath, so I prefer not to touch it. We're likely to
start caching guest segment fields soon, so the less code that reads
them directly, the better.

> Signed-off-by: Roel Kluin<roel.kluin@gmail.com>
> ---
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index 29f9129..5d8512a 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -1932,13 +1932,8 @@ static bool ldtr_valid(struct kvm_vcpu *vcpu)
>
> static bool cs_ss_rpl_check(struct kvm_vcpu *vcpu)
> {
> - struct kvm_segment cs, ss;
> -
> - vmx_get_segment(vcpu,&cs, VCPU_SREG_CS);
> - vmx_get_segment(vcpu,&ss, VCPU_SREG_SS);
> -
> - return ((cs.selector& SELECTOR_RPL_MASK) ==
> - (ss.selector& SELECTOR_RPL_MASK));
> + return ((vmcs_read16(GUEST_CS_SELECTOR)& SELECTOR_RPL_MASK) ==
> + (vmcs_read16(GUEST_SS_SELECTOR)& SELECTOR_RPL_MASK));
> }
>
> /*
>


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



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