diff options
author | David Woodhouse <dwmw@amazon.co.uk> | 2021-10-23 22:47:19 +0300 |
---|---|---|
committer | Paolo Bonzini <pbonzini@redhat.com> | 2021-10-25 16:10:18 +0300 |
commit | 0985dba842eaa391858972cfe2724c3c174a2827 (patch) | |
tree | e2ec913194408349c8ed528b6259090759b1a9df /arch | |
parent | 4b2caef043dd89dd98da282cd6b90af2cbb60650 (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.c | 27 |
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; } |