From e371f713db6523d99d8ffae8f9da564055e6de17 Mon Sep 17 00:00:00 2001 From: Alexander Graf Date: Mon, 19 Dec 2011 13:36:55 +0100 Subject: [PATCH] KVM: PPC: Book3S: PR: Fix signal check race As Scott put it: > If we get a signal after the check, we want to be sure that we don't > receive the reschedule IPI until after we're in the guest, so that it > will cause another signal check. we need to have interrupts disabled from the point we do signal_check() all the way until we actually enter the guest. This patch fixes potential signal loss races. Reported-by: Scott Wood Signed-off-by: Alexander Graf Signed-off-by: Avi Kivity --- arch/powerpc/kvm/book3s_pr.c | 20 ++++++++++++++++++++ 1 file changed, 20 insertions(+) diff --git a/arch/powerpc/kvm/book3s_pr.c b/arch/powerpc/kvm/book3s_pr.c index 0c31507..2da6704 100644 --- a/arch/powerpc/kvm/book3s_pr.c +++ b/arch/powerpc/kvm/book3s_pr.c @@ -51,6 +51,8 @@ static int kvmppc_handle_ext(struct kvm_vcpu *vcpu, unsigned int exit_nr, #define MSR_USER32 MSR_USER #define MSR_USER64 MSR_USER #define HW_PAGE_SIZE PAGE_SIZE +#define __hard_irq_disable local_irq_disable +#define __hard_irq_enable local_irq_enable #endif void kvmppc_core_vcpu_load(struct kvm_vcpu *vcpu, int cpu) @@ -776,7 +778,16 @@ program_interrupt: /* To avoid clobbering exit_reason, only check for signals if * we aren't already exiting to userspace for some other * reason. */ + + /* + * Interrupts could be timers for the guest which we have to + * inject again, so let's postpone them until we're in the guest + * and if we really did time things so badly, then we just exit + * again due to a host external interrupt. + */ + __hard_irq_disable(); if (signal_pending(current)) { + __hard_irq_enable(); #ifdef EXIT_DEBUG printk(KERN_EMERG "KVM: Going back to host\n"); #endif @@ -959,8 +970,17 @@ int kvmppc_vcpu_run(struct kvm_run *kvm_run, struct kvm_vcpu *vcpu) kvmppc_core_prepare_to_enter(vcpu); + /* + * Interrupts could be timers for the guest which we have to inject + * again, so let's postpone them until we're in the guest and if we + * really did time things so badly, then we just exit again due to + * a host external interrupt. + */ + __hard_irq_disable(); + /* No need to go into the guest when all we do is going out */ if (signal_pending(current)) { + __hard_irq_enable(); kvm_run->exit_reason = KVM_EXIT_INTR; ret = -EINTR; goto out; -- 2.7.4