KVM: x86: accept userspace interrupt only if no event is injected

stable inclusion
from stable-5.10.58
commit 309a31127befd0c9809036f3ea500fcf662f2bf3
bugzilla: 176984 https://gitee.com/openeuler/kernel/issues/I4E2P4

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=309a31127befd0c9809036f3ea500fcf662f2bf3

--------------------------------

commit fa7a549d upstream.

Once an exception has been injected, any side effects related to
the exception (such as setting CR2 or DR6) have been taked place.
Therefore, once KVM sets the VM-entry interruption information
field or the AMD EVENTINJ field, the next VM-entry must deliver that
exception.

Pending interrupts are processed after injected exceptions, so
in theory it would not be a problem to use KVM_INTERRUPT when
an injected exception is present.  However, DOSEMU is using
run->ready_for_interrupt_injection to detect interrupt windows
and then using KVM_SET_SREGS/KVM_SET_REGS to inject the
interrupt manually.  For this to work, the interrupt window
must be delayed after the completion of the previous event
injection.

Cc: stable@vger.kernel.org
Reported-by: NStas Sergeev <stsp2@yandex.ru>
Tested-by: NStas Sergeev <stsp2@yandex.ru>
Fixes: 71cc849b ("KVM: x86: Fix split-irqchip vs interrupt injection window request")
Reviewed-by: NSean Christopherson <seanjc@google.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NChen Jun <chenjun102@huawei.com>
Acked-by: NWeilong Chen <chenweilong@huawei.com>
Signed-off-by: NChen Jun <chenjun102@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>

arch/x86/kvm/x86.c

@@ -4167,8 +4167,17 @@ static int kvm_cpu_accept_dm_intr(struct kvm_vcpu *vcpu)
 
 static int kvm_vcpu_ready_for_interrupt_injection(struct kvm_vcpu *vcpu)
 {
-	return kvm_arch_interrupt_allowed(vcpu) &&
-		kvm_cpu_accept_dm_intr(vcpu);
+	/*
+	 * Do not cause an interrupt window exit if an exception
+	 * is pending or an event needs reinjection; userspace
+	 * might want to inject the interrupt manually using KVM_SET_REGS
+	 * or KVM_SET_SREGS.  For that to work, we must be at an
+	 * instruction boundary and with no events half-injected.
+	 */
+	return (kvm_arch_interrupt_allowed(vcpu) &&
+		kvm_cpu_accept_dm_intr(vcpu) &&
+		!kvm_event_needs_reinjection(vcpu) &&
+		!vcpu->arch.exception.pending);
 }
 
 static int kvm_vcpu_ioctl_interrupt(struct kvm_vcpu *vcpu,