From patchwork Wed Dec 18 16:01:32 2013 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Alexander Graf X-Patchwork-Id: 302961 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 86AB32C00B5 for ; Thu, 19 Dec 2013 03:01:59 +1100 (EST) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755146Ab3LRQB5 (ORCPT ); Wed, 18 Dec 2013 11:01:57 -0500 Received: from cantor2.suse.de ([195.135.220.15]:58040 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754967Ab3LRQBn (ORCPT ); Wed, 18 Dec 2013 11:01:43 -0500 Received: from relay1.suse.de (charybdis-ext.suse.de [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id 0AA71AC3E; Wed, 18 Dec 2013 16:01:41 +0000 (UTC) From: Alexander Graf To: kvm-ppc@vger.kernel.org Cc: "kvm@vger.kernel.org mailing list" , Paolo Bonzini , Gleb Natapov Subject: [PULL 06/12] KVM: PPC: Book3S: PR: Don't clobber our exit handler id Date: Wed, 18 Dec 2013 17:01:32 +0100 Message-Id: <1387382498-19817-7-git-send-email-agraf@suse.de> X-Mailer: git-send-email 1.8.1.4 In-Reply-To: <1387382498-19817-1-git-send-email-agraf@suse.de> References: <1387382498-19817-1-git-send-email-agraf@suse.de> Sender: kvm-ppc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm-ppc@vger.kernel.org We call a C helper to save all svcpu fields into our vcpu. The C ABI states that r12 is considered volatile. However, we keep our exit handler id in r12 currently. So we need to save it away into a non-volatile register instead that definitely does get preserved across the C call. This bug usually didn't hit anyone yet since gcc is smart enough to generate code that doesn't even need r12 which means it stayed identical throughout the call by sheer luck. But we can't rely on that. Signed-off-by: Alexander Graf --- arch/powerpc/kvm/book3s_interrupts.S | 13 ++++++++++--- 1 file changed, 10 insertions(+), 3 deletions(-) diff --git a/arch/powerpc/kvm/book3s_interrupts.S b/arch/powerpc/kvm/book3s_interrupts.S index f4dd041..5e7cb32 100644 --- a/arch/powerpc/kvm/book3s_interrupts.S +++ b/arch/powerpc/kvm/book3s_interrupts.S @@ -132,9 +132,17 @@ kvm_start_lightweight: * */ + PPC_LL r3, GPR4(r1) /* vcpu pointer */ + + /* + * kvmppc_copy_from_svcpu can clobber volatile registers, save + * the exit handler id to the vcpu and restore it from there later. + */ + stw r12, VCPU_TRAP(r3) + /* Transfer reg values from shadow vcpu back to vcpu struct */ /* On 64-bit, interrupts are still off at this point */ - PPC_LL r3, GPR4(r1) /* vcpu pointer */ + GET_SHADOW_VCPU(r4) bl FUNC(kvmppc_copy_from_svcpu) nop @@ -151,7 +159,6 @@ kvm_start_lightweight: */ ld r3, PACA_SPRG3(r13) mtspr SPRN_SPRG3, r3 - #endif /* CONFIG_PPC_BOOK3S_64 */ /* R7 = vcpu */ @@ -177,7 +184,7 @@ kvm_start_lightweight: PPC_STL r31, VCPU_GPR(R31)(r7) /* Pass the exit number as 3rd argument to kvmppc_handle_exit */ - mr r5, r12 + lwz r5, VCPU_TRAP(r7) /* Restore r3 (kvm_run) and r4 (vcpu) */ REST_2GPRS(3, r1)