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authorDavid Woodhouse <dwmw@amazon.co.uk>2021-10-23 20:47:19 +0100
committerPaolo Bonzini <pbonzini@redhat.com>2021-10-25 09:10:18 -0400
commit0985dba842eaa391858972cfe2724c3c174a2827 (patch)
treee2ec913194408349c8ed528b6259090759b1a9df /arch
parent4b2caef043dd89dd98da282cd6b90af2cbb60650 (diff)
KVM: x86/xen: Fix kvm_xen_has_interrupt() sleeping in kvm_vcpu_block()
In kvm_vcpu_block, the current task is set to TASK_INTERRUPTIBLE before making a final check whether the vCPU should be woken from HLT by any incoming interrupt. This is a problem for the get_user() in __kvm_xen_has_interrupt(), which really shouldn't be sleeping when the task state has already been set. I think it's actually harmless as it would just manifest itself as a spurious wakeup, but it's causing a debug warning: [ 230.963649] do not call blocking ops when !TASK_RUNNING; state=1 set at [<00000000b6bcdbc9>] prepare_to_swait_exclusive+0x30/0x80 Fix the warning by turning it into an *explicit* spurious wakeup. When invoked with !task_is_running(current) (and we might as well add in_atomic() there while we're at it), just return 1 to indicate that an IRQ is pending, which will cause a wakeup and then something will call it again in a context that *can* sleep so it can fault the page back in. Cc: stable@vger.kernel.org Fixes: 40da8ccd724f ("KVM: x86/xen: Add event channel interrupt vector upcall") Signed-off-by: David Woodhouse <dwmw@amazon.co.uk> Message-Id: <168bf8c689561da904e48e2ff5ae4713eaef9e2d.camel@infradead.org> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'arch')
-rw-r--r--arch/x86/kvm/xen.c27
1 files changed, 22 insertions, 5 deletions
diff --git a/arch/x86/kvm/xen.c b/arch/x86/kvm/xen.c
index 9ea9c3dabe37..8f62baebd028 100644
--- a/arch/x86/kvm/xen.c
+++ b/arch/x86/kvm/xen.c
@@ -190,6 +190,7 @@ void kvm_xen_update_runstate_guest(struct kvm_vcpu *v, int state)
int __kvm_xen_has_interrupt(struct kvm_vcpu *v)
{
+ int err;
u8 rc = 0;
/*
@@ -216,13 +217,29 @@ int __kvm_xen_has_interrupt(struct kvm_vcpu *v)
if (likely(slots->generation == ghc->generation &&
!kvm_is_error_hva(ghc->hva) && ghc->memslot)) {
/* Fast path */
- __get_user(rc, (u8 __user *)ghc->hva + offset);
- } else {
- /* Slow path */
- kvm_read_guest_offset_cached(v->kvm, ghc, &rc, offset,
- sizeof(rc));
+ pagefault_disable();
+ err = __get_user(rc, (u8 __user *)ghc->hva + offset);
+ pagefault_enable();
+ if (!err)
+ return rc;
}
+ /* Slow path */
+
+ /*
+ * This function gets called from kvm_vcpu_block() after setting the
+ * task to TASK_INTERRUPTIBLE, to see if it needs to wake immediately
+ * from a HLT. So we really mustn't sleep. If the page ended up absent
+ * at that point, just return 1 in order to trigger an immediate wake,
+ * and we'll end up getting called again from a context where we *can*
+ * fault in the page and wait for it.
+ */
+ if (in_atomic() || !task_is_running(current))
+ return 1;
+
+ kvm_read_guest_offset_cached(v->kvm, ghc, &rc, offset,
+ sizeof(rc));
+
return rc;
}