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>

3 files changed, 51 insertions, 0 deletions

diff --git a/drivers/kvm/kvm.h b/drivers/kvm/kvm.h
index be3a0e7ecae4..1c4a581938bf 100644
--- 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 ac44df551aa8..df85f5f65489 100644
--- 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 b3af92e7bf5d..c0d10cd8088e 100644
--- 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