Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758917AbcCVKwR (ORCPT ); Tue, 22 Mar 2016 06:52:17 -0400 Received: from youngberry.canonical.com ([91.189.89.112]:56967 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758683AbcCVKnH (ORCPT ); Tue, 22 Mar 2016 06:43:07 -0400 From: Luis Henriques To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Cc: Paul Mackerras , Luis Henriques Subject: [PATCH 3.16.y-ckt 121/142] KVM: PPC: Book3S HV: Sanitize special-purpose register values on guest exit Date: Tue, 22 Mar 2016 10:40:50 +0000 Message-Id: <1458643271-4227-122-git-send-email-luis.henriques@canonical.com> In-Reply-To: <1458643271-4227-1-git-send-email-luis.henriques@canonical.com> References: <1458643271-4227-1-git-send-email-luis.henriques@canonical.com> X-Extended-Stable: 3.16 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1916 Lines: 53 3.16.7-ckt26 -stable review patch. If anyone has any objections, please let me know. ---8<------------------------------------------------------------ From: Paul Mackerras commit ccec44563b18a0ce90e2d4f332784b3cb25c8e9c upstream. Thomas Huth discovered that a guest could cause a hard hang of a host CPU by setting the Instruction Authority Mask Register (IAMR) to a suitable value. It turns out that this is because when the code was added to context-switch the new special-purpose registers (SPRs) that were added in POWER8, we forgot to add code to ensure that they were restored to a sane value on guest exit. This adds code to set those registers where a bad value could compromise the execution of the host kernel to a suitable neutral value on guest exit. Fixes: b005255e12a3 Reported-by: Thomas Huth Reviewed-by: David Gibson Signed-off-by: Paul Mackerras Signed-off-by: Luis Henriques --- arch/powerpc/kvm/book3s_hv_rmhandlers.S | 14 ++++++++++++++ 1 file changed, 14 insertions(+) diff --git a/arch/powerpc/kvm/book3s_hv_rmhandlers.S b/arch/powerpc/kvm/book3s_hv_rmhandlers.S index 6fafff75f24a..f3197994b733 100644 --- a/arch/powerpc/kvm/book3s_hv_rmhandlers.S +++ b/arch/powerpc/kvm/book3s_hv_rmhandlers.S @@ -1280,6 +1280,20 @@ END_FTR_SECTION_IFCLR(CPU_FTR_ARCH_207S) std r6, VCPU_ACOP(r9) stw r7, VCPU_GUEST_PID(r9) std r8, VCPU_WORT(r9) + /* + * Restore various registers to 0, where non-zero values + * set by the guest could disrupt the host. + */ + li r0, 0 + mtspr SPRN_IAMR, r0 + mtspr SPRN_CIABR, r0 + mtspr SPRN_DAWRX, r0 + mtspr SPRN_TCSCR, r0 + mtspr SPRN_WORT, r0 + /* Set MMCRS to 1<<31 to freeze and disable the SPMC counters */ + li r0, 1 + sldi r0, r0, 31 + mtspr SPRN_MMCRS, r0 8: /* Save and reset AMR and UAMOR before turning on the MMU */