From: Jan Beulich <jbeulich@suse.com>
To: Roger Pau Monne <roger.pau@citrix.com>
Cc: xen-devel@lists.xenproject.org,
George Dunlap <george.dunlap@citrix.com>, Wei Liu <wl@xen.org>,
Andrew Cooper <andrew.cooper3@citrix.com>
Subject: Re: [Xen-devel] [PATCH v6 3/6] x86/hap: improve hypervisor assisted guest TLB flush
Date: Thu, 5 Mar 2020 16:38:41 +0100 [thread overview]
Message-ID: <1e908189-ffff-796c-9cc3-39260bd1120f@suse.com> (raw)
In-Reply-To: <20200303172046.50569-4-roger.pau@citrix.com>
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@citrix.com>
> Reviewed-by: Wei Liu <wl@xen.org>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
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next prev parent reply other threads:[~2020-03-05 15:38 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-03 17:20 [Xen-devel] [PATCH v6 0/6] x86: improve assisted tlb flush and use it in guest mode Roger Pau Monne
2020-03-03 17:20 ` [Xen-devel] [PATCH v6 1/6] x86/hvm: allow ASID flush when v != current Roger Pau Monne
2020-03-03 17:20 ` [Xen-devel] [PATCH v6 2/6] x86/paging: add TLB flush hooks Roger Pau Monne
2020-03-03 17:26 ` Durrant, Paul
2020-03-05 15:37 ` Jan Beulich
2020-03-03 17:20 ` [Xen-devel] [PATCH v6 3/6] x86/hap: improve hypervisor assisted guest TLB flush Roger Pau Monne
2020-03-05 15:38 ` Jan Beulich [this message]
2020-03-03 17:20 ` [Xen-devel] [PATCH v6 4/6] x86/tlb: introduce a flush guests TLB flag Roger Pau Monne
2020-03-06 9:28 ` Jan Beulich
2020-03-03 17:20 ` [Xen-devel] [PATCH v6 5/6] x86/tlb: allow disabling the TLB clock Roger Pau Monne
2020-03-03 17:20 ` [Xen-devel] [PATCH v6 6/6] x86/tlb: use Xen L0 assisted TLB flush when available Roger Pau Monne
2020-03-06 9:32 ` Jan Beulich
2020-03-19 15:40 ` Roger Pau Monné
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