From patchwork Sun Feb 5 19:21:01 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Willy Tarreau X-Patchwork-Id: 9556937 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id D13E1604DA for ; Sun, 5 Feb 2017 20:31:57 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id C442824B44 for ; Sun, 5 Feb 2017 20:31:57 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id B8BDF2621D; Sun, 5 Feb 2017 20:31:57 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.9 required=2.0 tests=BAYES_00,RCVD_IN_DNSWL_HI autolearn=unavailable version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 5CDC624B44 for ; Sun, 5 Feb 2017 20:31:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752379AbdBETWI (ORCPT ); Sun, 5 Feb 2017 14:22:08 -0500 Received: from wtarreau.pck.nerim.net ([62.212.114.60]:27351 "EHLO 1wt.eu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752315AbdBETWG (ORCPT ); Sun, 5 Feb 2017 14:22:06 -0500 Received: (from willy@localhost) by pcw.home.local (8.15.2/8.15.2/Submit) id v15JL9jj008016; Sun, 5 Feb 2017 20:21:09 +0100 From: Willy Tarreau To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, linux@roeck-us.net Cc: James Hogan , Paolo Bonzini , =?UTF-8?q?=20Radim=20Kr=C4=8Dm=C3=A1=C5=99?= , Ralf Baechle , linux-mips@linux-mips.org, kvm@vger.kernel.org, Willy Tarreau Subject: [PATCH 3.10 023/319] KVM: MIPS: Precalculate MMIO load resume PC Date: Sun, 5 Feb 2017 20:21:01 +0100 Message-Id: <1486322467-7968-1-git-send-email-w@1wt.eu> X-Mailer: git-send-email 2.8.0.rc2.1.gbe9624a MIME-Version: 1.0 Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP From: James Hogan commit e1e575f6b026734be3b1f075e780e91ab08ca541 upstream. The advancing of the PC when completing an MMIO load is done before re-entering the guest, i.e. before restoring the guest ASID. However if the load is in a branch delay slot it may need to access guest code to read the prior branch instruction. This isn't safe in TLB mapped code at the moment, nor in the future when we'll access unmapped guest segments using direct user accessors too, as it could read the branch from host user memory instead. Therefore calculate the resume PC in advance while we're still in the right context and save it in the new vcpu->arch.io_pc (replacing the no longer needed vcpu->arch.pending_load_cause), and restore it on MMIO completion. Fixes: e685c689f3a8 ("KVM/MIPS32: Privileged instruction/target branch emulation.") Signed-off-by: James Hogan Cc: Paolo Bonzini Cc: "Radim Krčmář Cc: Ralf Baechle Cc: linux-mips@linux-mips.org Cc: kvm@vger.kernel.org Cc: Cc: Signed-off-by: Paolo Bonzini [james.hogan@imgtec.com: Backport to 3.10..3.16] Signed-off-by: James Hogan Signed-off-by: Willy Tarreau --- arch/mips/include/asm/kvm_host.h | 7 ++++--- arch/mips/kvm/kvm_mips_emul.c | 25 +++++++++++++++---------- 2 files changed, 19 insertions(+), 13 deletions(-) diff --git a/arch/mips/include/asm/kvm_host.h b/arch/mips/include/asm/kvm_host.h index 883a162..05863e3 100644 --- a/arch/mips/include/asm/kvm_host.h +++ b/arch/mips/include/asm/kvm_host.h @@ -375,7 +375,10 @@ struct kvm_vcpu_arch { /* Host KSEG0 address of the EI/DI offset */ void *kseg0_commpage; - u32 io_gpr; /* GPR used as IO source/target */ + /* Resume PC after MMIO completion */ + unsigned long io_pc; + /* GPR used as IO source/target */ + u32 io_gpr; /* Used to calibrate the virutal count register for the guest */ int32_t host_cp0_count; @@ -386,8 +389,6 @@ struct kvm_vcpu_arch { /* Bitmask of pending exceptions to be cleared */ unsigned long pending_exceptions_clr; - unsigned long pending_load_cause; - /* Save/Restore the entryhi register when are are preempted/scheduled back in */ unsigned long preempt_entryhi; diff --git a/arch/mips/kvm/kvm_mips_emul.c b/arch/mips/kvm/kvm_mips_emul.c index 5c2d70b..e5977f2 100644 --- a/arch/mips/kvm/kvm_mips_emul.c +++ b/arch/mips/kvm/kvm_mips_emul.c @@ -773,6 +773,7 @@ kvm_mips_emulate_load(uint32_t inst, uint32_t cause, struct kvm_run *run, struct kvm_vcpu *vcpu) { enum emulation_result er = EMULATE_DO_MMIO; + unsigned long curr_pc; int32_t op, base, rt, offset; uint32_t bytes; @@ -781,7 +782,18 @@ kvm_mips_emulate_load(uint32_t inst, uint32_t cause, offset = inst & 0xffff; op = (inst >> 26) & 0x3f; - vcpu->arch.pending_load_cause = cause; + /* + * Find the resume PC now while we have safe and easy access to the + * prior branch instruction, and save it for + * kvm_mips_complete_mmio_load() to restore later. + */ + curr_pc = vcpu->arch.pc; + er = update_pc(vcpu, cause); + if (er == EMULATE_FAIL) + return er; + vcpu->arch.io_pc = vcpu->arch.pc; + vcpu->arch.pc = curr_pc; + vcpu->arch.io_gpr = rt; switch (op) { @@ -1617,9 +1629,8 @@ kvm_mips_complete_mmio_load(struct kvm_vcpu *vcpu, struct kvm_run *run) goto done; } - er = update_pc(vcpu, vcpu->arch.pending_load_cause); - if (er == EMULATE_FAIL) - return er; + /* Restore saved resume PC */ + vcpu->arch.pc = vcpu->arch.io_pc; switch (run->mmio.len) { case 4: @@ -1641,12 +1652,6 @@ kvm_mips_complete_mmio_load(struct kvm_vcpu *vcpu, struct kvm_run *run) break; } - if (vcpu->arch.pending_load_cause & CAUSEF_BD) - kvm_debug - ("[%#lx] Completing %d byte BD Load to gpr %d (0x%08lx) type %d\n", - vcpu->arch.pc, run->mmio.len, vcpu->arch.io_gpr, *gpr, - vcpu->mmio_needed); - done: return er; }