From: Paolo Bonzini
> Sent: 10 April 2019 10:55
>
> This check will soon be done on every nested vmentry and vmexit,
> "parallelize" it using bitwise operations.
>
> Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> ---
...
> diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h
> index 28406aa1136d..7bc7ac9d2a44 100644
> --- a/arch/x86/kvm/x86.h
> +++ b/arch/x86/kvm/x86.h
> @@ -347,4 +347,12 @@ static inline void kvm_after_interrupt(struct kvm_vcpu *vcpu)
> __this_cpu_write(current_vcpu, NULL);
> }
>
> +static inline bool kvm_pat_valid(u64 data)
> +{
> + if (data & 0xF8F8F8F8F8F8F8F8)
> + return false;
> + /* 0, 1, 4, 5, 6, 7 are valid values. */
> + return (data | ((data & 0x0202020202020202) << 1)) == data;
> +}
> +
How about:
/*
* Each byte must be 0, 1, 4, 5, 6 or 7.
* Convert 001x to 011x then 100x so 2 and 3 fail the test.
*/
data |= (data ^ 0x0404040404040404ULL)) + 0x0202020202020202ULL;
if (data & 0xF8F8F8F8F8F8F8F8ULL)
return false;
David
-
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