Re: [Xen-devel] [PATCH v2 4/6] xen/x86/pvh: Set up descriptors for 32-bit PVH guests

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Thu, Jul 16, 2015 at 05:43:39PM -0400, Boris Ostrovsky wrote:
> Signed-off-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
> ---
> Changes in v2:
> * Set segment selectors using loadsegment() instead of assembly
> 
>  arch/x86/xen/enlighten.c | 15 ++++++++++-----
>  1 file changed, 10 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
> index f8dc398..d665b1d 100644
> --- a/arch/x86/xen/enlighten.c
> +++ b/arch/x86/xen/enlighten.c
> @@ -1362,12 +1362,12 @@ static void __init xen_boot_params_init_edd(void)
>  static void __ref xen_setup_gdt(int cpu)
>  {
>       if (xen_feature(XENFEAT_auto_translated_physmap)) {
> -#ifdef CONFIG_X86_64
> -             unsigned long dummy;
> +             unsigned long __attribute__((unused)) dummy;
>  
> -             load_percpu_segment(cpu); /* We need to access per-cpu area */

You removed that - where are we going to do that? As the
'switch_to_new_gdt' uses the per-cpu GDT table.

> +             setup_stack_canary_segment(cpu);

As this one too ?
>               switch_to_new_gdt(cpu); /* GDT and GS set */
>  
> +#ifdef CONFIG_X86_64
>               /* We are switching of the Xen provided GDT to our HVM mode
>                * GDT. The new GDT has  __KERNEL_CS with CS.L = 1
>                * and we are jumping to reload it.
> @@ -1392,8 +1392,13 @@ static void __ref xen_setup_gdt(int cpu)
>               loadsegment(ds, 0);
>               loadsegment(fs, 0);
>  #else
> -             /* PVH: TODO Implement. */
> -             BUG();
> +             asm volatile ("ljmp %0,$1f\n"
> +                           "1:\n"
> +                           :: "i" (__KERNEL_CS));
> +
> +             loadsegment(ss, __KERNEL_DS);
> +             loadsegment(ds, __USER_DS);
> +             loadsegment(es, __USER_DS);
>  #endif
>               return; /* PVH does not need any PV GDT ops. */
>       }
> -- 
> 1.8.1.4
> 

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