Re: [PATCH 1/4] stubs for xsavec support

[Jan Kiszka <jan.kiszka@siemens.com>]

On 2015-01-08 11:32, Paolo Bonzini wrote:
> These are needed for KVM changes in 3.18.
> 
> Recent kernels added a separate feature word for XSAVE features, and KVM's
> CPUID code is relying on the new definition.  Except for cpu_has_xsaves,
> it's never accessing the feature itself: wrap cpu_has_xsaves with
> kvm_cpu_has_xsaves, and then there is no problem with out-of-bounds
> accesses.
> 
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> ---
>  external-module-compat-comm.h |  4 ++++
>  external-module-compat.c      | 11 +++++++++++
>  sync                          | 14 ++++++++++++--
>  x86/external-module-compat.h  | 37 +++++++++++++++++++++++++++++++++++++
>  4 files changed, 64 insertions(+), 2 deletions(-)
> 

...

> diff --git a/x86/external-module-compat.h b/x86/external-module-compat.h
> index dec53b6..87cf76a 100644
> --- a/x86/external-module-compat.h
> +++ b/x86/external-module-compat.h
> @@ -428,6 +428,23 @@ static inline int rdmsrl_safe(unsigned msr, unsigned long long *p)
>  #define X86_FEATURE_MPX		(9*32+14) /* Memory Protection Extension */
>  #endif
>  
> +#if X86_FEATURE_XSAVEOPT < 10 * 32
> +#undef X86_FEATURE_XSAVEOPT
> +#endif
> +#define X86_FEATURE_XSAVEOPT	(10*32+0) /* XSAVEOPT instruction */

This causes redefinition warnings if the condition is not met. Was the
plan to put the define before the #endif?

Jan

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