From e764a21b89a14dd291428e0275d685a3d8419d1d Mon Sep 17 00:00:00 2001 From: Dean Nelson Date: Fri, 15 Oct 2010 21:17:35 -0300 Subject: [RHEL6 qemu-kvm PATCH 4/7] Ignore SRAO MCE if another MCE is being processed RH-Author: Dean Nelson Message-id: <20101015211735.4348.60230.send-patch@localhost6.localdomain6> Patchwork-id: 12689 O-Subject: [RHEL6.1 qemu-kvm PATCH v2 2/5] Ignore SRAO MCE if another MCE is being processed Bugzilla: 585910 RH-Acked-by: Jes Sorensen RH-Acked-by: Marcelo Tosatti RH-Acked-by: Eduardo Habkost Resolves RHBZ 585910. In common cases, guest SRAO MCE will cause corresponding poisoned page be un-mapped in host and SIGBUS be sent to QEMU-KVM, then QEMU-KVM will relay the MCE to guest OS. But it is possible that the poisoned page is accessed in guest after un-mapped in host and before MCE is relayed to guest OS. So that, the SRAR SIGBUS is sent to QEMU-KVM before the SRAO SIGBUS, and if QEMU-KVM relays them to guest OS one by one, guest system may reset, because the SRAO MCE may be triggered while the SRAR MCE is being processed. In fact, the SRAO MCE can be ignored in this situation, so that the guest system is given opportunity to survive. Backport of upstream commit: http://git.kernel.org/?p=virt/kvm/qemu-kvm.git;a=commitdiff;h=fb3ba1008cd9af6c7e03ca1d22ec1a904d9719a9 --- qemu-kvm.c | 28 ++++++++++++++++++++++++++++ 1 files changed, 28 insertions(+), 0 deletions(-) Signed-off-by: Eduardo Habkost --- qemu-kvm.c | 28 ++++++++++++++++++++++++++++ 1 files changed, 28 insertions(+), 0 deletions(-) diff --git a/qemu-kvm.c b/qemu-kvm.c index 717957e..b34f131 100644 --- a/qemu-kvm.c +++ b/qemu-kvm.c @@ -1685,6 +1685,19 @@ static void flush_queued_work(CPUState *env) pthread_cond_broadcast(&qemu_work_cond); } +static int kvm_mce_in_exception(CPUState *env) +{ + struct kvm_msr_entry msr_mcg_status = { + .index = MSR_MCG_STATUS, + }; + int r; + + r = kvm_get_msrs(env, &msr_mcg_status, 1); + if (r == -1 || r == 0) + return -1; + return !!(msr_mcg_status.data & MCG_STATUS_MCIP); +} + static void kvm_on_sigbus(CPUState *env, siginfo_t *siginfo) { #if defined(KVM_CAP_MCE) && defined(TARGET_I386) @@ -1705,6 +1718,15 @@ static void kvm_on_sigbus(CPUState *env, siginfo_t *siginfo) mce.misc = (MCM_ADDR_PHYS << 6) | 0xc; mce.mcg_status = MCG_STATUS_MCIP | MCG_STATUS_EIPV; } else { + /* + * If there is an MCE excpetion being processed, ignore + * this SRAO MCE + */ + r = kvm_mce_in_exception(env); + if (r == -1) + fprintf(stderr, "Failed to get MCE status\n"); + else if (r) + return; /* Fake an Intel architectural Memory scrubbing UCR */ mce.status = MCI_STATUS_VAL | MCI_STATUS_UC | MCI_STATUS_EN | MCI_STATUS_MISCV | MCI_STATUS_ADDRV | MCI_STATUS_S @@ -2638,6 +2660,12 @@ static void kvm_do_inject_x86_mce(void *_data) struct kvm_x86_mce_data *data = _data; int r; + /* If there is an MCE excpetion being processed, ignore this SRAO MCE */ + r = kvm_mce_in_exception(data->env); + if (r == -1) + fprintf(stderr, "Failed to get MCE status\n"); + else if (r && !(data->mce->status & MCI_STATUS_AR)) + return; r = kvm_set_mce(data->env, data->mce); if (r < 0) { perror("kvm_set_mce FAILED"); -- 1.6.5.5