From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail333.us4.mandrillapp.com ([205.201.137.77]:53200 "EHLO mail333.us4.mandrillapp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752535AbcCAWX0 (ORCPT ); Tue, 1 Mar 2016 17:23:26 -0500 Received: from pmta03.dal05.mailchimp.com (127.0.0.1) by mail333.us4.mandrillapp.com id hqob5s174noc for ; Tue, 1 Mar 2016 22:23:24 +0000 (envelope-from ) From: Subject: Patch "KVM: x86: fix missed hardware breakpoints" has been added to the 4.4-stable tree To: , , , Cc: , Message-Id: <14568710004856@kroah.com> Date: Tue, 01 Mar 2016 22:23:23 +0000 MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Sender: stable-owner@vger.kernel.org List-ID: This is a note to let you know that I've just added the patch titled KVM: x86: fix missed hardware breakpoints to the 4.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: kvm-x86-fix-missed-hardware-breakpoints.patch and it can be found in the queue-4.4 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let know about it. >>From 172b2386ed16a9143d9a456aae5ec87275c61489 Mon Sep 17 00:00:00 2001 From: Paolo Bonzini Date: Wed, 10 Feb 2016 17:50:23 +0100 Subject: KVM: x86: fix missed hardware breakpoints From: Paolo Bonzini commit 172b2386ed16a9143d9a456aae5ec87275c61489 upstream. Sometimes when setting a breakpoint a process doesn't stop on it. This is because the debug registers are not loaded correctly on VCPU load. The following simple reproducer from Oleg Nesterov tries using debug registers in two threads. To see the bug, run a 2-VCPU guest with "taskset -c 0" and run "./bp 0 1" inside the guest. #include #include #include #include #include #include #include #include #include #define offsetof(TYPE, MEMBER) ((size_t) &((TYPE *)0)->MEMBER) unsigned long encode_dr7(int drnum, int enable, unsigned int type, unsigned int len) { unsigned long dr7; dr7 = ((len | type) & 0xf) << (DR_CONTROL_SHIFT + drnum * DR_CONTROL_SIZE); if (enable) dr7 |= (DR_GLOBAL_ENABLE << (drnum * DR_ENABLE_SIZE)); return dr7; } int write_dr(int pid, int dr, unsigned long val) { return ptrace(PTRACE_POKEUSER, pid, offsetof (struct user, u_debugreg[dr]), val); } void set_bp(pid_t pid, void *addr) { unsigned long dr7; assert(write_dr(pid, 0, (long)addr) == 0); dr7 = encode_dr7(0, 1, DR_RW_EXECUTE, DR_LEN_1); assert(write_dr(pid, 7, dr7) == 0); } void *get_rip(int pid) { return (void*)ptrace(PTRACE_PEEKUSER, pid, offsetof(struct user, regs.rip), 0); } void test(int nr) { void *bp_addr = &&label + nr, *bp_hit; int pid; printf("test bp %d\n", nr); assert(nr < 16); // see 16 asm nops below pid = fork(); if (!pid) { assert(ptrace(PTRACE_TRACEME, 0,0,0) == 0); kill(getpid(), SIGSTOP); for (;;) { label: asm ( "nop; nop; nop; nop;" "nop; nop; nop; nop;" "nop; nop; nop; nop;" "nop; nop; nop; nop;" ); } } assert(pid == wait(NULL)); set_bp(pid, bp_addr); for (;;) { assert(ptrace(PTRACE_CONT, pid, 0, 0) == 0); assert(pid == wait(NULL)); bp_hit = get_rip(pid); if (bp_hit != bp_addr) fprintf(stderr, "ERR!! hit wrong bp %ld != %d\n", bp_hit - &&label, nr); } } int main(int argc, const char *argv[]) { while (--argc) { int nr = atoi(*++argv); if (!fork()) test(nr); } while (wait(NULL) > 0) ; return 0; } Suggested-by: Nadav Amit Reported-by: Andrey Wagin Signed-off-by: Paolo Bonzini Signed-off-by: Greg Kroah-Hartman --- arch/x86/kvm/x86.c | 1 + 1 file changed, 1 insertion(+) --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -2736,6 +2736,7 @@ void kvm_arch_vcpu_load(struct kvm_vcpu } kvm_make_request(KVM_REQ_STEAL_UPDATE, vcpu); + vcpu->arch.switch_db_regs |= KVM_DEBUGREG_RELOAD; } void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu) Patches currently in stable-queue which might be from pbonzini@redhat.com are queue-4.4/kvm-x86-fix-conversion-of-addresses-to-linear-in-32-bit-protected-mode.patch queue-4.4/kvm-x86-mmu-fix-ubsan-index-out-of-range-warning.patch queue-4.4/kvm-x86-fix-missed-hardware-breakpoints.patch queue-4.4/kvm-async_pf-do-not-warn-on-page-allocation-failures.patch