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

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) )
#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).


Julien Grall

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