Re: [Xen-devel] [PATCH v6 3/6] x86/hap: improve hypervisor assisted guest TLB flush

[Jan Beulich <jbeulich@xxxxxxxx>]

On 03.03.2020 18:20, Roger Pau Monne wrote:
> The current implementation of the hypervisor assisted flush for HAP is
> extremely inefficient.
> 
> First of all there's no need to call paging_update_cr3, as the only
> relevant part of that function when doing a flush is the ASID vCPU
> flush, so just call that function directly.
> 
> Since hvm_asid_flush_vcpu is protected against concurrent callers by
> using atomic operations there's no need anymore to pause the affected
> vCPUs.
> 
> Finally the global TLB flush performed by flush_tlb_mask is also not
> necessary, since we only want to flush the guest TLB state it's enough
> to trigger a vmexit on the pCPUs currently holding any vCPU state, as
> such vmexit will already perform an ASID/VPID update, and thus clear
> the guest TLB.
> 
> Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
> Reviewed-by: Wei Liu <wl@xxxxxxx>

Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>

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