Re: [Xen-devel] [PATCH 4/5] x86/pv: Simplify access to the LDT/GDT ptes

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 29.08.17 at 13:19, <andrew.cooper3@xxxxxxxxxx> wrote:
> Rename gdt_ldt_ptes() to pv_gdt_ptes() and drop the domain parameter, as it is
> incorrect to use the helper with d != v->domain.

Indeed, but it was still done this way for a reason:

> --- a/xen/include/asm-x86/domain.h
> +++ b/xen/include/asm-x86/domain.h
> @@ -432,9 +432,10 @@ struct arch_domain
>  
>  #define gdt_ldt_pt_idx(v) \
>        ((v)->vcpu_id >> (PAGETABLE_ORDER - GDT_LDT_VCPU_SHIFT))
> -#define gdt_ldt_ptes(d, v) \
> -    ((d)->arch.pv_domain.gdt_ldt_l1tab[gdt_ldt_pt_idx(v)] + \
> +#define pv_gdt_ptes(v) \
> +    ((v)->domain->arch.pv_domain.gdt_ldt_l1tab[gdt_ldt_pt_idx(v)] + \

When the caller has latched v->domain into a local (register)
variable, the compiler normally can't know that v->domain
doesn't need to be re-read. But anyway, this isn't important
enough to block the change, so
Acked-by: Jan Beulich <jbeulich@xxxxxxxx>

Jan


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
https://lists.xen.org/xen-devel