Re: [Xen-devel] [PATCH 9/9] x86/shim: pass through vcpu runstate to L0 Xen

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

On Thu, Jan 18, 2018 at 06:16:52PM +0000, Wei Liu wrote:
> diff --git a/xen/common/domain.c b/xen/common/domain.c
> index 558318e852..189ffac9b1 100644
> --- a/xen/common/domain.c
> +++ b/xen/common/domain.c
> @@ -45,6 +45,7 @@
>  
>  #ifdef CONFIG_X86
>  #include <asm/guest.h>
> +#include <asm/guest/hypercall.h>
>  #endif
>  
>  /* Linux config option: propageted to domain0 */
> @@ -1425,6 +1426,15 @@ long do_vcpu_op(int cmd, unsigned int vcpuid, 
> XEN_GUEST_HANDLE_PARAM(void) arg)
>          if ( !guest_handle_okay(area.addr.h, 1) )
>              break;
>  
> +#if CONFIG_X86
> +        if ( pv_shim )
> +        {
> +            rc = xen_hypercall_vcpu_op(VCPUOP_register_runstate_memory_area,
> +                                       vcpuid, &area);
> +            break;
> +        }
> +#endif

This only fixes VCPUOP_register_runstate_memory_area, but
VCPUOP_get_runstate_info will still report wrong information. I've
also wondered whether simply returning L0 information is correct. To
get the exact information the shim should actually return the L0
information plus whatever time it steals from the guest.

Also, before adding more hooks to do_vcpu_op I would attempt to add a
pv_shim_do_vcpu_op helper and patch the hypercall table, in order to
avoid modifying more common code. AFAICT this doesn't require adding
much compat code to the shim implementation.

Thanks, Roger.

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