From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:51356) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1alq7b-0008Mo-KR for qemu-devel@nongnu.org; Thu, 31 Mar 2016 23:51:44 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1alq7X-0002X4-Ak for qemu-devel@nongnu.org; Thu, 31 Mar 2016 23:51:43 -0400 From: David Gibson Date: Fri, 1 Apr 2016 14:52:47 +1100 Message-Id: <1459482767-12573-1-git-send-email-david@gibson.dropbear.id.au> Subject: [Qemu-devel] [PATCH] target-ppc: Correct KVM synchronization for ppc_hash64_set_external_hpt() List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: agraf@suse.de, pbonzini@redhat.com, aik@ozlabs.ru Cc: lvivier@redhat.com, peter.maydell@linaro.org, mdroth@linux.vnet.ibm.com, qemu-devel@nongnu.org, qemu-ppc@nongnu.org, David Gibson ppc_hash64_set_external_hpt() was added in e5c0d3c "target-ppc: Add helpers for updating a CPU's SDR1 and external HPT". This helper contains a cpu_synchronize_state() since it may need to push state back to KVM afterwards. This turns out to break things when it is used in the reset path, which is the only current user. It appears that kvm_vcpu_dirty is not being set early in the reset path, so the cpu_synchronize_state() is clobbering state set up by the early part of the cpu reset path with stale state from KVM. To fix this, remove the cpu_synchronize_state() from ppc_hash64_set_external_hpt(). Any future non-reset-path users will need to manually invoke cpu_synchronize_state(). Reported-by: Laurent Vivier Signed-off-by: David Gibson --- target-ppc/mmu-hash64.c | 2 -- 1 file changed, 2 deletions(-) Paolo, Peter, This seems like the right minimal fix in the qemu-2.6 timeframe to fix the actual bug. However, longer term it seems like the correct thing to do might be to set kvm_vcpu_dirty early in the reset path. Thoughts? diff --git a/target-ppc/mmu-hash64.c b/target-ppc/mmu-hash64.c index 72c4ab5..caf41ce 100644 --- a/target-ppc/mmu-hash64.c +++ b/target-ppc/mmu-hash64.c @@ -283,8 +283,6 @@ void ppc_hash64_set_external_hpt(PowerPCCPU *cpu, void *hpt, int shift, CPUPPCState *env = &cpu->env; Error *local_err = NULL; - cpu_synchronize_state(CPU(cpu)); - if (hpt) { env->external_htab = hpt; } else { -- 2.5.5