From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932526AbcHUPmD (ORCPT ); Sun, 21 Aug 2016 11:42:03 -0400 Received: from wtarreau.pck.nerim.net ([62.212.114.60]:55914 "EHLO 1wt.eu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932520AbcHUPgK (ORCPT ); Sun, 21 Aug 2016 11:36:10 -0400 From: Willy Tarreau To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: James Hogan , Paolo Bonzini , =?UTF-8?q?Radim=20Kr=C4=8Dm=C3=A1=C5=99?= , Ralf Baechle , kvm@vger.kernel.org, linux-mips@linux-mips.org, stable@vger.kernel.org#3.10.x-, Greg Kroah-Hartman , Willy Tarreau Subject: [PATCH 3.10 058/180] MIPS: KVM: Fix modular KVM under QEMU Date: Sun, 21 Aug 2016 17:29:48 +0200 Message-Id: <1471793510-13022-59-git-send-email-w@1wt.eu> X-Mailer: git-send-email 2.8.0.rc2.1.gbe9624a In-Reply-To: <1471793510-13022-1-git-send-email-w@1wt.eu> References: <1471793510-13022-1-git-send-email-w@1wt.eu> MIME-Version: 1.0 Content-Type: text/plain; charset=latin1 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: James Hogan commit 797179bc4fe06c89e47a9f36f886f68640b423f8 upstream. Copy __kvm_mips_vcpu_run() into unmapped memory, so that we can never get a TLB refill exception in it when KVM is built as a module. This was observed to happen with the host MIPS kernel running under QEMU, due to a not entirely transparent optimisation in the QEMU TLB handling where TLB entries replaced with TLBWR are copied to a separate part of the TLB array. Code in those pages continue to be executable, but those mappings persist only until the next ASID switch, even if they are marked global. An ASID switch happens in __kvm_mips_vcpu_run() at exception level after switching to the guest exception base. Subsequent TLB mapped kernel instructions just prior to switching to the guest trigger a TLB refill exception, which enters the guest exception handlers without updating EPC. This appears as a guest triggered TLB refill on a host kernel mapped (host KSeg2) address, which is not handled correctly as user (guest) mode accesses to kernel (host) segments always generate address error exceptions. Signed-off-by: James Hogan Cc: Paolo Bonzini Cc: Radim Krčmář Cc: Ralf Baechle Cc: kvm@vger.kernel.org Cc: linux-mips@linux-mips.org Cc: # 3.10.x- Signed-off-by: Paolo Bonzini [james.hogan@imgtec.com: backported for stable 3.14] Signed-off-by: James Hogan Signed-off-by: Greg Kroah-Hartman Signed-off-by: Willy Tarreau --- arch/mips/include/asm/kvm_host.h | 1 + arch/mips/kvm/kvm_locore.S | 1 + arch/mips/kvm/kvm_mips.c | 11 ++++++++++- arch/mips/kvm/kvm_mips_int.h | 2 ++ 4 files changed, 14 insertions(+), 1 deletion(-) diff --git a/arch/mips/include/asm/kvm_host.h b/arch/mips/include/asm/kvm_host.h index 4d6fa0b..883a162 100644 --- a/arch/mips/include/asm/kvm_host.h +++ b/arch/mips/include/asm/kvm_host.h @@ -349,6 +349,7 @@ struct kvm_mips_tlb { #define KVM_MIPS_GUEST_TLB_SIZE 64 struct kvm_vcpu_arch { void *host_ebase, *guest_ebase; + int (*vcpu_run)(struct kvm_run *run, struct kvm_vcpu *vcpu); unsigned long host_stack; unsigned long host_gp; diff --git a/arch/mips/kvm/kvm_locore.S b/arch/mips/kvm/kvm_locore.S index 34c35f0..73553cd 100644 --- a/arch/mips/kvm/kvm_locore.S +++ b/arch/mips/kvm/kvm_locore.S @@ -227,6 +227,7 @@ FEXPORT(__kvm_mips_load_k0k1) /* Jump to guest */ eret .set pop +EXPORT(__kvm_mips_vcpu_run_end) VECTOR(MIPSX(exception), unknown) /* diff --git a/arch/mips/kvm/kvm_mips.c b/arch/mips/kvm/kvm_mips.c index 8aa5f30..97a181a 100644 --- a/arch/mips/kvm/kvm_mips.c +++ b/arch/mips/kvm/kvm_mips.c @@ -343,6 +343,15 @@ struct kvm_vcpu *kvm_arch_vcpu_create(struct kvm *kvm, unsigned int id) memcpy(gebase + offset, mips32_GuestException, mips32_GuestExceptionEnd - mips32_GuestException); +#ifdef MODULE + offset += mips32_GuestExceptionEnd - mips32_GuestException; + memcpy(gebase + offset, (char *)__kvm_mips_vcpu_run, + __kvm_mips_vcpu_run_end - (char *)__kvm_mips_vcpu_run); + vcpu->arch.vcpu_run = gebase + offset; +#else + vcpu->arch.vcpu_run = __kvm_mips_vcpu_run; +#endif + /* Invalidate the icache for these ranges */ mips32_SyncICache((unsigned long) gebase, ALIGN(size, PAGE_SIZE)); @@ -426,7 +435,7 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *run) kvm_guest_enter(); - r = __kvm_mips_vcpu_run(run, vcpu); + r = vcpu->arch.vcpu_run(run, vcpu); kvm_guest_exit(); local_irq_enable(); diff --git a/arch/mips/kvm/kvm_mips_int.h b/arch/mips/kvm/kvm_mips_int.h index 20da7d2..bf41ea3 100644 --- a/arch/mips/kvm/kvm_mips_int.h +++ b/arch/mips/kvm/kvm_mips_int.h @@ -27,6 +27,8 @@ #define MIPS_EXC_MAX 12 /* XXXSL More to follow */ +extern char __kvm_mips_vcpu_run_end[]; + #define C_TI (_ULCAST_(1) << 30) #define KVM_MIPS_IRQ_DELIVER_ALL_AT_ONCE (0) -- 2.8.0.rc2.1.gbe9624a