Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753360Ab3FIIpm (ORCPT ); Sun, 9 Jun 2013 04:45:42 -0400 Received: from mx1.redhat.com ([209.132.183.28]:10595 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753234Ab3FIIp3 (ORCPT ); Sun, 9 Jun 2013 04:45:29 -0400 Date: Sun, 9 Jun 2013 11:45:26 +0300 From: Gleb Natapov To: Xiao Guangrong Cc: Paolo Bonzini , Marcelo Tosatti , LKML , KVM Subject: Re: [PATCH] KVM: x86: fix missed memory synchronization when patch hypercall Message-ID: <20130609084526.GH4725@redhat.com> References: <51B2A1D9.6060306@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <51B2A1D9.6060306@gmail.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3847 Lines: 109 On Sat, Jun 08, 2013 at 11:15:37AM +0800, Xiao Guangrong wrote: > From: Xiao Guangrong > > Currently, memory synchronization is missed in emulator_fix_hypercall, > please see the commit 758ccc89b83 > (KVM: x86: drop calling kvm_mmu_zap_all in emulator_fix_hypercall) > > This patch fixes it by introducing kvm_vcpus_hang_on_page_start() and > kvm_vcpus_hang_on_page_end which unmap the patched page from guest > and use kvm_flush_remote_tlbs() as the serializing instruction to > ensure the memory coherence > [ The SDM said that INVEPT, INVVPID and MOV (to control register, with > the exception of MOV CR8) are the serializing instructions. ] > > The mmu-lock is held during host patches the page so that it stops vcpus > to fix its further page fault > I have a patch to implement is much simple and in generic way, not relying on MMU internals. diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 6402951..49774ab 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -5517,7 +5517,7 @@ out: } EXPORT_SYMBOL_GPL(kvm_emulate_hypercall); -static int emulator_fix_hypercall(struct x86_emulate_ctxt *ctxt) +static int emulator_fix_hypercall_cb(void *ctxt) { struct kvm_vcpu *vcpu = emul_to_vcpu(ctxt); char instruction[3]; @@ -5528,6 +5528,14 @@ static int emulator_fix_hypercall(struct x86_emulate_ctxt *ctxt) return emulator_write_emulated(ctxt, rip, instruction, 3, NULL); } +static int emulator_fix_hypercall(struct x86_emulate_ctxt *ctxt) +{ + struct kvm_vcpu *vcpu = emul_to_vcpu(ctxt); + return kvm_exec_with_stopped_vcpu(vcpu->kvm, + emulator_fix_hypercall_cb, ctxt); +} + + /* * Check if userspace requested an interrupt window, and that the * interrupt window is open. @@ -5761,6 +5769,10 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu) kvm_deliver_pmi(vcpu); if (kvm_check_request(KVM_REQ_SCAN_IOAPIC, vcpu)) vcpu_scan_ioapic(vcpu); + if (kvm_check_request(KVM_REQ_STOP_VCPU, vcpu)){ + mutex_lock(&vcpu->kvm->lock); + mutex_unlock(&vcpu->kvm->lock); + } } if (kvm_check_request(KVM_REQ_EVENT, vcpu) || req_int_win) { diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h index e3aae6d..6c9361a 100644 --- a/include/linux/kvm_host.h +++ b/include/linux/kvm_host.h @@ -125,6 +125,7 @@ static inline bool is_error_page(struct page *page) #define KVM_REQ_EPR_EXIT 20 #define KVM_REQ_SCAN_IOAPIC 21 #define KVM_REQ_GLOBAL_CLOCK_UPDATE 22 +#define KVM_REQ_STOP_VCPU 23 #define KVM_USERSPACE_IRQ_SOURCE_ID 0 #define KVM_IRQFD_RESAMPLE_IRQ_SOURCE_ID 1 @@ -576,6 +577,7 @@ void kvm_flush_remote_tlbs(struct kvm *kvm); void kvm_reload_remote_mmus(struct kvm *kvm); void kvm_make_mclock_inprogress_request(struct kvm *kvm); void kvm_make_scan_ioapic_request(struct kvm *kvm); +int kvm_exec_with_stopped_vcpu(struct kvm *kvm, int (*cb)(void *), void *data); long kvm_arch_dev_ioctl(struct file *filp, unsigned int ioctl, unsigned long arg); diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index 1580dd4..531e765 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -222,6 +222,18 @@ void kvm_make_scan_ioapic_request(struct kvm *kvm) make_all_cpus_request(kvm, KVM_REQ_SCAN_IOAPIC); } +int kvm_exec_with_stopped_vcpu(struct kvm *kvm, int (*cb)(void *), void *data) +{ + int r; + + mutex_lock(&kvm->lock); + make_all_cpus_request(kvm, KVM_REQ_STOP_VCPU); + r = cb(data); + mutex_unlock(&kvm->lock); + + return r; +} + int kvm_vcpu_init(struct kvm_vcpu *vcpu, struct kvm *kvm, unsigned id) { struct page *page; -- Gleb. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/