Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753402AbcKYJMA (ORCPT ); Fri, 25 Nov 2016 04:12:00 -0500 Received: from mx2.suse.de ([195.135.220.15]:45213 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751218AbcKYIaq (ORCPT ); Fri, 25 Nov 2016 03:30:46 -0500 X-Amavis-Alert: BAD HEADER SECTION, Duplicate header field: "References" From: Jiri Slaby To: stable@vger.kernel.org Cc: linux-kernel@vger.kernel.org, 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, Jiri Slaby Subject: [PATCH 3.12 004/127] KVM: MIPS: Precalculate MMIO load resume PC Date: Fri, 25 Nov 2016 09:28:37 +0100 Message-Id: X-Mailer: git-send-email 2.10.2 In-Reply-To: References: In-Reply-To: References: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4103 Lines: 121 From: James Hogan 3.12-stable review patch. If anyone has any objections, please let me know. =============== 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 Signed-off-by: Paolo Bonzini [james.hogan@imgtec.com: Backport to 3.10..3.16] Signed-off-by: James Hogan Signed-off-by: Jiri Slaby --- 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 883a162083af..05863e3ee2e7 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 779a376c4cce..4cfb5bddaa9b 100644 --- a/arch/mips/kvm/kvm_mips_emul.c +++ b/arch/mips/kvm/kvm_mips_emul.c @@ -818,6 +818,7 @@ 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; @@ -826,7 +827,18 @@ 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) { @@ -1662,9 +1674,8 @@ 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: @@ -1686,12 +1697,6 @@ 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; } -- 2.10.2