Re: [Xen-devel] [PATCH v7 1/3] x86/tlb: introduce a flush HVM ASIDs flag

[Julien Grall <julien@xxxxxxx>]

On 20/03/2020 14:22, Roger Pau Monné wrote:
> static inline void filtered_flush_tlb_mask(uint32_t tlbflush_timestamp)
> {
>      cpumask_t mask;
>
>      cpumask_copy(&mask, &cpu_online_map);
>      tlbflush_filter(&mask, tlbflush_timestamp);
>      if ( !cpumask_empty(&mask) )
>      {
>          perfc_incr(need_flush_tlb_flush);
> #if CONFIG_X86
>          /*
>           * filtered_flush_tlb_mask is used after modifying the p2m in
>           * populate_physmap, Xen needs to trigger an ASID tickle as this is a
>           * requirement on AMD hardware.
>           */
I don't think this comment is correct. populate_physmap() is only going 
to add entry in the P2M and therefore flush should not be needed.
The only reason the flush would happen in populate_physmap() is because 
we allocated a page that was required to be flush (see free.need_tbflush).
Cheers,

--
Julien Grall

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