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Thu, 10 Sep 2020 09:27:55 -0400 X-MC-Unique: GGMbtMqWME-oXJaqIo8ZqA-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 2B93B425D2; Thu, 10 Sep 2020 13:27:54 +0000 (UTC) Received: from work-vm (ovpn-113-128.ams2.redhat.com [10.36.113.128]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 6612F19C59; Thu, 10 Sep 2020 13:27:51 +0000 (UTC) Date: Thu, 10 Sep 2020 14:27:48 +0100 From: "Dr. David Alan Gilbert" To: Andrew Jones Subject: Re: [PATCH v2 0/2] MTE support for KVM guest Message-ID: <20200910132748.GF2814@work-vm> References: <20200904160018.29481-1-steven.price@arm.com> <20200909152540.ylnrljd6aelxoxrf@kamzik.brq.redhat.com> <5cb1d7ed-54a5-4337-6c3d-2e3e7df89f17@linaro.org> <20200910054440.pvnzk7p7riiy45e2@kamzik.brq.redhat.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20200910054440.pvnzk7p7riiy45e2@kamzik.brq.redhat.com> User-Agent: Mutt/1.14.6 (2020-07-11) X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200910_092802_114763_08FB4EE0 X-CRM114-Status: GOOD ( 22.22 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Peter Maydell , linux-kernel@vger.kernel.org, Juan Quintela , Catalin Marinas , Richard Henderson , qemu-devel@nongnu.org, Steven Price , Marc Zyngier , Thomas Gleixner , Will Deacon , kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org, Dave Martin Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org * Andrew Jones (drjones@redhat.com) wrote: > On Wed, Sep 09, 2020 at 06:45:33PM -0700, Richard Henderson wrote: > > On 9/9/20 8:25 AM, Andrew Jones wrote: > > >> * Provide a KVM-specific method to extract the tags from guest memory. > > >> This might also have benefits in terms of providing an easy way to > > >> read bulk tag data from guest memory (since the LDGM instruction > > >> isn't available at EL0). > > > > > > Maybe we need a new version of KVM_GET_DIRTY_LOG that also provides > > > the tags for all addresses of each dirty page. > > > > KVM_GET_DIRTY_LOG just provides one bit per dirty page, no? Then VMM copies > > the data out from its local address to guest memory. > > > > There'd be no difference with or without tags, afaik. It's just about how VMM > > copies the data, with or without tags. > > Right, as long as it's fast enough to do > > for_each_dirty_page(page, dirty_log) > for (i = 0; i < host-page-size/16; i += 16) > append_tag(LDG(page + i)) > > to get all the tags for each dirty page. I understood it would be faster > to use LDGM, but we'd need a new ioctl for that. So I was proposing we > just piggyback on a new dirty-log ioctl instead. That feels a bad idea to me; there's a couple of different ways dirty page checking work; lets keep extracting the tags separate. Dave > Thanks, > drew -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel