Re: [Xen-devel] [PATCH 8/18 V2]: PVH xen: domain creation code changes

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 16.03.13 at 01:36, Mukesh Rathor <mukesh.rathor@xxxxxxxxxx> wrote:
> --- a/xen/include/asm-x86/system.h
> +++ b/xen/include/asm-x86/system.h
> @@ -4,9 +4,15 @@
>  #include <xen/lib.h>
>  #include <asm/bitops.h>
>  
> +/* We need vcpu because during context switch, going from pure PV to PVH,
> + * in save_segments(), current has been updated to next, and no longer 
> pointing
> + * to the pure PV. Note: for PVH, we update regs->selectors on each vmexit */
>  #define read_segment_register(vcpu, regs, name)                 \
>  ({  u16 __sel;                                                  \
> -    asm volatile ( "movw %%" STR(name) ",%0" : "=r" (__sel) );  \
> +    if (is_pvh_vcpu(vcpu))                                         \
> +        __sel = regs->name;                                     \
> +    else                                                         \
> +        asm volatile ( "movw %%" STR(name) ",%0" : "=r" (__sel) );  \
>      __sel;                                                      \
>  })

In a generic macro like this, please make sure you evaluate each
argument exactly once, and you properly parenthesize all uses of
macro arguments.

Jan


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