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Thu, 6 Feb 2020 16:03:09 +0000 (UTC) Date: Thu, 6 Feb 2020 11:03:08 -0500 From: Eduardo Habkost To: Babu Moger Subject: Re: [PATCH] i386: pass CLZERO to guests with EPYC CPU model on AMD ZEN platform Message-ID: <20200206160308.GB25446@habkost.net> References: <1576659933-37123-1-git-send-email-ani.sinha@nutanix.com> <2883fd0e-191a-c5a4-be1c-04442c8de1c9@redhat.com> <20191218151144.GN498046@habkost.net> <20200205223731.GY25446@habkost.net> <60B21C9A-30BE-4DC0-8A1B-0BC7757BA9D7@nutanix.com> <78f5dad9-5433-3f7c-69cb-db496b1c37a7@amd.com> MIME-Version: 1.0 In-Reply-To: <78f5dad9-5433-3f7c-69cb-db496b1c37a7@amd.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-MC-Unique: 2voJA1sWOfe-YOYBkf1UsA-1 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Content-Disposition: inline X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 205.139.110.61 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Paolo Bonzini , Ani Sinha , "qemu-devel@nongnu.org" , "Singh, Brijesh" , "rth@twiddle.net" Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Thu, Feb 06, 2020 at 09:30:11AM -0600, Babu Moger wrote: >=20 >=20 > On 2/5/20 11:53 PM, Ani Sinha wrote: > >=20 > >=20 > >> On Feb 6, 2020, at 11:16 AM, Ani Sinha wrote: > >> > >> > >> > >>> On Feb 6, 2020, at 5:30 AM, Moger, Babu wrote: > >>> > >>> Ani, I am already working on it. > >> > >> Wow, I see a whole new AMD-Rome CPU model with it=E2=80=99s own cache = info data :=20 > >> > >> https://nam11.safelinks.protection.outlook.com/?url=3Dhttps%3A%2F%2Flo= re.kernel.org%2Fqemu-devel%2F157314966312.23828.17684821666338093910.stgit%= 40naples-babu.amd.com%2F&data=3D02%7C01%7CBabu.Moger%40amd.com%7Cc566dc= 5cf3cc407b5ee608d7aac8d9bc%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637= 165651955089264&sdata=3DtlafWD6m5%2BZ12cqd4vqJcWh0%2FIgly%2FPVMgAbjxK5M= og%3D&reserved=3D0 > >=20 > > Do you think the ROME specific guest cpu cache data will have significa= nt impact on performance? >=20 > I have not done performance benchmarks myself. Yes. Rome is expected to > perform better than its previous generations. Note that virtual cache information on CPUID doesn't affect host software or hardware behavior in any way. In the exceptional cases it affects performance, it's solely because guest software behavior changed depending on the cache information it sees. --=20 Eduardo