From: "Roger Pau Monné" <email@example.com> To: Jan Beulich <firstname.lastname@example.org> Cc: email@example.com, Paul Durrant <firstname.lastname@example.org>, Wei Liu <email@example.com>, Andrew Cooper <firstname.lastname@example.org> Subject: Re: [Xen-devel] [PATCH v2 0/3] x86: improve assisted tlb flush and use it in guest mode Date: Fri, 10 Jan 2020 17:14:44 +0100 [thread overview] Message-ID: <20200110161444.GD11756@Air-de-Roger> (raw) In-Reply-To: <email@example.com> On Fri, Jan 10, 2020 at 05:08:16PM +0100, Jan Beulich wrote: > On 10.01.2020 17:04, Roger Pau Monne wrote: > > Patch #2 is likely the most controversial one, as it changes the > > implementation of assisted TLB flushes. I have to admit I haven't been > > able to figure out why HVM guest context flushes issued a > > flush_tlb_mask, and the commit introducing such behavior doesn't contain > > a helpful commit message. > > A shadow mode thing, maybe? Hm, I could be wrong, but that flush doesn't seem to make sense for shadow mode either. If VPID/ASID is used, ticking it will drop all the guest caches, and if VPID/ASID not used a vmexit/vmentry will clear the cache. According to my reading of the Intel SDM this applies regardless of whether HAP (EPT) is used or not. The flush done by flush_tlb_mask is in root mode, and hence doesn't affect the guest (non-root) caches when SVM/VTx is used. Roger. _______________________________________________ Xen-devel mailing list Xenfirstname.lastname@example.org https://lists.xenproject.org/mailman/listinfo/xen-devel
prev parent reply other threads:[~2020-01-10 16:15 UTC|newest] Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-01-10 16:04 Roger Pau Monne 2020-01-10 16:04 ` [Xen-devel] [PATCH v2 1/3] x86/hvm: allow ASID flush when v != current Roger Pau Monne 2020-01-10 16:04 ` [Xen-devel] [PATCH v2 2/3] x86/hvm: rework HVMOP_flush_tlbs Roger Pau Monne 2020-01-10 16:04 ` [Xen-devel] [PATCH v2 3/3] x86/tlb: use Xen L0 assisted TLB flush when available Roger Pau Monne 2020-01-10 16:08 ` [Xen-devel] [PATCH v2 0/3] x86: improve assisted tlb flush and use it in guest mode Jan Beulich 2020-01-10 16:14 ` Roger Pau Monné [this message]
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