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Thu, 01 Apr 2021 02:47:55 -0700 (PDT) Received: from localhost ([1.128.222.172]) by smtp.gmail.com with ESMTPSA id ch15sm4703580pjb.46.2021.04.01.02.47.54 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 01 Apr 2021 02:47:55 -0700 (PDT) Date: Thu, 01 Apr 2021 19:47:49 +1000 From: Nicholas Piggin Subject: Re: [PATCH v4 09/46] powerpc/64s: remove KVM SKIP test from instruction breakpoint handler To: Paul Mackerras References: <20210323010305.1045293-1-npiggin@gmail.com> <20210323010305.1045293-10-npiggin@gmail.com> In-Reply-To: MIME-Version: 1.0 Message-Id: <1617270447.zkb024siva.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: Fabiano Rosas , linuxppc-dev@lists.ozlabs.org, kvm-ppc@vger.kernel.org, Daniel Axtens Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" Excerpts from Paul Mackerras's message of March 31, 2021 2:54 pm: > On Tue, Mar 23, 2021 at 11:02:28AM +1000, Nicholas Piggin wrote: >> The code being executed in KVM_GUEST_MODE_SKIP is hypervisor code with >> MSR[IR]=3D0, so the faults of concern are the d-side ones caused by acce= ss >> to guest context by the hypervisor. >>=20 >> Instruction breakpoint interrupts are not a concern here. It's unlikely >> any good would come of causing breaks in this code, but skipping the >> instruction that caused it won't help matters (e.g., skip the mtmsr that >> sets MSR[DR]=3D0 or clears KVM_GUEST_MODE_SKIP). >>=20 >> Reviewed-by: Daniel Axtens >> Reviewed-by: Fabiano Rosas >> Signed-off-by: Nicholas Piggin >=20 > It might be worth noting in the commit message that the 0x1300 > interrupt was dropped from the architecture a long time ago and is not > generated by P7, P8, P9 or P10. Good background, I'll add that. Thanks, Nick >=20 > Acked-by: Paul Mackerras >=20