Re: [Xen-devel] [PATCH v2 1/3] x86/hypervisor: pass flags to hypervisor_flush_tlb

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

On Fri, Feb 14, 2020 at 12:34:28PM +0000, Wei Liu wrote:
> Hyper-V's L0 assisted flush has fine-grained control over what gets
> flushed. We need all the flags available to make the best decisions
> possible.
> 
> No functional change because Xen's implementation doesn't care about
> what is passed to it.
> 
> Signed-off-by: Wei Liu <liuwe@xxxxxxxxxxxxx>

LGTM:

Reviewed-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>

Just one comment below.

> ---
> v2:
> 1. Introduce FLUSH_TLB_FLAGS_MASK
> ---
>  xen/arch/x86/guest/hypervisor.c        |  7 +++++--
>  xen/arch/x86/guest/xen/xen.c           |  2 +-
>  xen/arch/x86/smp.c                     |  5 ++---
>  xen/include/asm-x86/flushtlb.h         |  3 +++
>  xen/include/asm-x86/guest/hypervisor.h | 10 +++++-----
>  5 files changed, 16 insertions(+), 11 deletions(-)
> 
> diff --git a/xen/arch/x86/guest/hypervisor.c b/xen/arch/x86/guest/hypervisor.c
> index 47e938e287..6ee28c9df1 100644
> --- a/xen/arch/x86/guest/hypervisor.c
> +++ b/xen/arch/x86/guest/hypervisor.c
> @@ -75,10 +75,13 @@ void __init hypervisor_e820_fixup(struct e820map *e820)
>  }
>  
>  int hypervisor_flush_tlb(const cpumask_t *mask, const void *va,
> -                         unsigned int order)
> +                         unsigned int flags)
>  {
> +    if ( flags & ~FLUSH_TLB_FLAGS_MASK )

I think an ASSERT_UNREACHABLE() would be good here, since you are not
supposed to call hypervisor_flush_tlb with non TLB related flags.

Thanks, Roger.

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