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[61.68.186.125]) by smtp.gmail.com with ESMTPSA id v11sm40299584wmb.3.2020.06.30.04.57.12 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 30 Jun 2020 04:57:13 -0700 (PDT) Date: Tue, 30 Jun 2020 21:57:06 +1000 From: Nicholas Piggin Subject: Re: [PATCH 3/3] powerpc/pseries: Add KVM guest doorbell restrictions To: Paul Mackerras References: <20200627150428.2525192-1-npiggin@gmail.com> <20200627150428.2525192-4-npiggin@gmail.com> <20200630022713.GA618342@thinks.paulus.ozlabs.org> <1593495049.cacw882re0.astroid@bobo.none> <20200630082607.GB618342@thinks.paulus.ozlabs.org> In-Reply-To: <20200630082607.GB618342@thinks.paulus.ozlabs.org> MIME-Version: 1.0 Message-Id: <1593518201.ez0344yx91.astroid@bobo.none> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: kvm-ppc@vger.kernel.org, Anton Blanchard , =?iso-8859-1?q?C=E9dric?= Le Goater , linuxppc-dev@lists.ozlabs.org, David Gibson Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" Excerpts from Paul Mackerras's message of June 30, 2020 6:26 pm: > On Tue, Jun 30, 2020 at 03:35:08PM +1000, Nicholas Piggin wrote: >> Excerpts from Paul Mackerras's message of June 30, 2020 12:27 pm: >> > On Sun, Jun 28, 2020 at 01:04:28AM +1000, Nicholas Piggin wrote: >> >> KVM guests have certain restrictions and performance quirks when >> >> using doorbells. This patch tests for KVM environment in doorbell >> >> setup, and optimises IPI performance: >> >>=20 >> >> - PowerVM guests may now use doorbells even if they are secure. >> >>=20 >> >> - KVM guests no longer use doorbells if XIVE is available. >> >=20 >> > It seems, from the fact that you completely remove >> > kvm_para_available(), that you perhaps haven't tried building with >> > CONFIG_KVM_GUEST=3Dy. >>=20 >> It's still there and builds: >=20 > OK, good, I missed that. >=20 >> static inline int kvm_para_available(void) >> { >> return IS_ENABLED(CONFIG_KVM_GUEST) && is_kvm_guest(); >> } >>=20 >> but... >>=20 >> > Somewhat confusingly, that option is not used or >> > needed when building for a PAPR guest (i.e. the "pseries" platform) >> > but is used on non-IBM platforms using the "epapr" hypervisor >> > interface. >>=20 >> ... is_kvm_guest() returns false on !PSERIES now. >=20 > And therefore kvm_para_available() returns false on all the platforms > where the code that depends on it could actually be used. >=20 > It's not correct to assume that !PSERIES means not a KVM guest. Yep, thanks for catching it. >> Not intended >> to break EPAPR. I'm not sure of a good way to share this between >> EPAPR and PSERIES, I might just make a copy of it but I'll see. >=20 > OK, so you're doing a new version? Just sent. Thanks, Nick