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Mon, 22 Feb 2021 22:22:53 +0000 (GMT) Received: from b01ledav005.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id C2325AE05C; Mon, 22 Feb 2021 22:22:52 +0000 (GMT) Received: from localhost (unknown [9.160.141.72]) by b01ledav005.gho.pok.ibm.com (Postfix) with ESMTPS; Mon, 22 Feb 2021 22:22:52 +0000 (GMT) From: Fabiano Rosas To: Nicholas Piggin , kvm-ppc@vger.kernel.org Subject: Re: [PATCH 02/13] powerpc/64s: remove KVM SKIP test from instruction breakpoint handler In-Reply-To: <20210219063542.1425130-3-npiggin@gmail.com> References: <20210219063542.1425130-1-npiggin@gmail.com> <20210219063542.1425130-3-npiggin@gmail.com> Date: Mon, 22 Feb 2021 19:22:51 -0300 Message-ID: <87k0qzyc78.fsf@linux.ibm.com> MIME-Version: 1.0 Content-Type: text/plain X-TM-AS-GCONF: 00 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.369, 18.0.761 definitions=2021-02-22_07:2021-02-22, 2021-02-22 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 mlxscore=0 malwarescore=0 clxscore=1015 bulkscore=0 impostorscore=0 phishscore=0 mlxlogscore=999 lowpriorityscore=0 suspectscore=0 spamscore=0 priorityscore=1501 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000 definitions=main-2102220190 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: linuxppc-dev@lists.ozlabs.org, Nicholas Piggin Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" Nicholas Piggin writes: > The code being executed in KVM_GUEST_MODE_SKIP is hypervisor code with > MSR[IR]=0, so the faults of concern are the d-side ones caused by access > to guest context by the hypervisor. > > 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]=0 or clears KVM_GUEST_MODE_SKIP). > > Signed-off-by: Nicholas Piggin Reviewed-by: Fabiano Rosas > --- > arch/powerpc/kernel/exceptions-64s.S | 1 - > 1 file changed, 1 deletion(-) > > diff --git a/arch/powerpc/kernel/exceptions-64s.S b/arch/powerpc/kernel/exceptions-64s.S > index 5d0ad3b38e90..5bc689a546ae 100644 > --- a/arch/powerpc/kernel/exceptions-64s.S > +++ b/arch/powerpc/kernel/exceptions-64s.S > @@ -2597,7 +2597,6 @@ EXC_VIRT_NONE(0x5200, 0x100) > INT_DEFINE_BEGIN(instruction_breakpoint) > IVEC=0x1300 > #ifdef CONFIG_KVM_BOOK3S_PR_POSSIBLE > - IKVM_SKIP=1 > IKVM_REAL=1 > #endif > INT_DEFINE_END(instruction_breakpoint)