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Thu, 03 Oct 2019 19:53:52 -0700 (PDT) Received: from pasglop.ozlabs.ibm.com ([122.99.82.10]) by smtp.gmail.com with ESMTPSA id d20sm6920181pfq.88.2019.10.03.19.53.48 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 03 Oct 2019 19:53:51 -0700 (PDT) From: Jordan Niethe To: linuxppc-dev@lists.ozlabs.org Subject: [PATCH] powerpc/kvm: Fix kvmppc_vcore->in_guest value in kvmhv_switch_to_host Date: Fri, 4 Oct 2019 12:53:17 +1000 Message-Id: <20191004025317.19340-1-jniethe5@gmail.com> X-Mailer: git-send-email 2.20.1 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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: aik@ozlabs.ru, alistair@popple.id.au, patch-notifications@ellerman.id.au, kvm-ppc@vger.kernel.org, Jordan Niethe Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" kvmhv_switch_to_host() in arch/powerpc/kvm/book3s_hv_rmhandlers.S needs to set kvmppc_vcore->in_guest to 0 to signal secondary CPUs to continue. This happens after resetting the PCR. Before commit 13c7bb3c57dc ("powerpc/64s: Set reserved PCR bits"), r0 would always be 0 before it was stored to kvmppc_vcore->in_guest. However because of this change in the commit: /* Reset PCR */ ld r0, VCORE_PCR(r5) - cmpdi r0, 0 + LOAD_REG_IMMEDIATE(r6, PCR_MASK) + cmpld r0, r6 beq 18f - li r0, 0 - mtspr SPRN_PCR, r0 + mtspr SPRN_PCR, r6 18: /* Signal secondary CPUs to continue */ stb r0,VCORE_IN_GUEST(r5) We are no longer comparing r0 against 0 and loading it with 0 if it contains something else. Hence when we store r0 to kvmppc_vcore->in_guest, it might not be 0. This means that secondary CPUs will not be signalled to continue. Those CPUs get stuck and errors like the following are logged: KVM: CPU 1 seems to be stuck KVM: CPU 2 seems to be stuck KVM: CPU 3 seems to be stuck KVM: CPU 4 seems to be stuck KVM: CPU 5 seems to be stuck KVM: CPU 6 seems to be stuck KVM: CPU 7 seems to be stuck This can be reproduced with: $ for i in `seq 1 7` ; do chcpu -d $i ; done ; $ taskset -c 0 qemu-system-ppc64 -smp 8,threads=8 \ -M pseries,accel=kvm,kvm-type=HV -m 1G -nographic -vga none \ -kernel vmlinux -initrd initrd.cpio.xz Fix by making sure r0 is 0 before storing it to kvmppc_vcore->in_guest. Fixes: 13c7bb3c57dc ("powerpc/64s: Set reserved PCR bits") Reported-by: Alexey Kardashevskiy Signed-off-by: Jordan Niethe --- arch/powerpc/kvm/book3s_hv_rmhandlers.S | 1 + 1 file changed, 1 insertion(+) diff --git a/arch/powerpc/kvm/book3s_hv_rmhandlers.S b/arch/powerpc/kvm/book3s_hv_rmhandlers.S index 74a9cfe84aee..faebcbb8c4db 100644 --- a/arch/powerpc/kvm/book3s_hv_rmhandlers.S +++ b/arch/powerpc/kvm/book3s_hv_rmhandlers.S @@ -1921,6 +1921,7 @@ END_FTR_SECTION_IFSET(CPU_FTR_ARCH_207S) mtspr SPRN_PCR, r6 18: /* Signal secondary CPUs to continue */ + li r0, 0 stb r0,VCORE_IN_GUEST(r5) 19: lis r8,0x7fff /* MAX_INT@h */ mtspr SPRN_HDEC,r8 -- 2.20.1