KVM: Add guest mode signal mask

Allow a special signal mask to be used while executing in guest mode.  This
allows signals to be used to interrupt a vcpu without requiring signal
delivery to a userspace handler, which is quite expensive.  Userspace still
receives -EINTR and can get the signal via sigwait().

Signed-off-by: Avi Kivity <avi@qumranet.com>

diff --git a/drivers/kvm/kvm.h b/drivers/kvm/kvm.h
index be3a0e7..1c4a581 100644 (file)
--- a/drivers/kvm/kvm.h
+++ b/drivers/kvm/kvm.h
@@ -277,6 +277,9 @@ struct kvm_vcpu {
        gpa_t mmio_phys_addr;
        int pio_pending;
 
+       int sigset_active;
+       sigset_t sigset;
+
        struct {
                int active;
                u8 save_iopl;

diff --git a/drivers/kvm/kvm_main.c b/drivers/kvm/kvm_main.c
index ac44df5..df85f5f 100644 (file)
--- a/drivers/kvm/kvm_main.c
+++ b/drivers/kvm/kvm_main.c
@@ -1591,9 +1591,13 @@ static void complete_pio(struct kvm_vcpu *vcpu)
 static int kvm_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
 {
        int r;
+       sigset_t sigsaved;
 
        vcpu_load(vcpu);
 
+       if (vcpu->sigset_active)
+               sigprocmask(SIG_SETMASK, &vcpu->sigset, &sigsaved);
+
        /* re-sync apic's tpr */
        vcpu->cr8 = kvm_run->cr8;
 
@@ -1616,6 +1620,9 @@ static int kvm_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
 
        r = kvm_arch_ops->run(vcpu, kvm_run);
 
+       if (vcpu->sigset_active)
+               sigprocmask(SIG_SETMASK, &sigsaved, NULL);
+
        vcpu_put(vcpu);
        return r;
 }
@@ -2142,6 +2149,17 @@ out:
        return r;
 }
 
+static int kvm_vcpu_ioctl_set_sigmask(struct kvm_vcpu *vcpu, sigset_t *sigset)
+{
+       if (sigset) {
+               sigdelsetmask(sigset, sigmask(SIGKILL)|sigmask(SIGSTOP));
+               vcpu->sigset_active = 1;
+               vcpu->sigset = *sigset;
+       } else
+               vcpu->sigset_active = 0;
+       return 0;
+}
+
 static long kvm_vcpu_ioctl(struct file *filp,
                           unsigned int ioctl, unsigned long arg)
 {
@@ -2260,6 +2278,29 @@ static long kvm_vcpu_ioctl(struct file *filp,
                        goto out;
                break;
        }
+       case KVM_SET_SIGNAL_MASK: {
+               struct kvm_signal_mask __user *sigmask_arg = argp;
+               struct kvm_signal_mask kvm_sigmask;
+               sigset_t sigset, *p;
+
+               p = NULL;
+               if (argp) {
+                       r = -EFAULT;
+                       if (copy_from_user(&kvm_sigmask, argp,
+                                          sizeof kvm_sigmask))
+                               goto out;
+                       r = -EINVAL;
+                       if (kvm_sigmask.len != sizeof sigset)
+                               goto out;
+                       r = -EFAULT;
+                       if (copy_from_user(&sigset, sigmask_arg->sigset,
+                                          sizeof sigset))
+                               goto out;
+                       p = &sigset;
+               }
+               r = kvm_vcpu_ioctl_set_sigmask(vcpu, &sigset);
+               break;
+       }
        default:
                ;
        }

diff --git a/include/linux/kvm.h b/include/linux/kvm.h
index b3af92e..c0d10cd 100644 (file)
--- a/include/linux/kvm.h
+++ b/include/linux/kvm.h
@@ -234,6 +234,12 @@ struct kvm_cpuid {
        struct kvm_cpuid_entry entries[0];
 };
 
+/* for KVM_SET_SIGNAL_MASK */
+struct kvm_signal_mask {
+       __u32 len;
+       __u8  sigset[0];
+};
+
 #define KVMIO 0xAE
 
 /*
@@ -273,5 +279,6 @@ struct kvm_cpuid {
 #define KVM_GET_MSRS              _IOWR(KVMIO, 0x88, struct kvm_msrs)
 #define KVM_SET_MSRS              _IOW(KVMIO,  0x89, struct kvm_msrs)
 #define KVM_SET_CPUID             _IOW(KVMIO,  0x8a, struct kvm_cpuid)
+#define KVM_SET_SIGNAL_MASK       _IOW(KVMIO,  0x8b, struct kvm_signal_mask)
 
 #endif