On Sat, 2022-04-23 at 02:14 +0000, Sean Christopherson wrote:
> From: Maciej S. Szmigiero <maciej.szmigiero@xxxxxxxxxx>
>
> Don't BUG/WARN on interrupt injection due to GIF being cleared if the
> injected event is a soft interrupt, which are not actually IRQs and thus
Are any injected events subject to GIF set? I think that EVENTINJ just injects
unconditionaly whatever hypervisor puts in it.
Best regards,
Maxim Levitsky
> not subject to IRQ blocking conditions. KVM doesn't currently use event
> injection to handle incomplete soft interrupts, but it's trivial for
> userspace to force the situation via KVM_SET_VCPU_EVENTS.
>
> Opportunistically downgrade the BUG_ON() to WARN_ON(), there's no need to
> bring down the whole host just because there might be some issue with
> respect to guest GIF handling in KVM, or as evidenced here, an egregious
> oversight with respect to KVM's uAPI.
>
> kernel BUG at arch/x86/kvm/svm/svm.c:3386!
> invalid opcode: 0000 [#1] SMP
> CPU: 15 PID: 926 Comm: smm_test Not tainted 5.17.0-rc3+ #264
> Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015
> RIP: 0010:svm_inject_irq+0xab/0xb0 [kvm_amd]
> Code: <0f> 0b 0f 1f 00 0f 1f 44 00 00 80 3d ac b3 01 00 00 55 48 89 f5 53
> RSP: 0018:ffffc90000b37d88 EFLAGS: 00010246
> RAX: 0000000000000000 RBX: ffff88810a234ac0 RCX: 0000000000000006
> RDX: 0000000000000000 RSI: ffffc90000b37df7 RDI: ffff88810a234ac0
> RBP: ffffc90000b37df7 R08: ffff88810a1fa410 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
> R13: ffff888109571000 R14: ffff88810a234ac0 R15: 0000000000000000
> FS: 0000000001821380(0000) GS:ffff88846fdc0000(0000) knlGS:0000000000000000
> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00007f74fc550008 CR3: 000000010a6fe000 CR4: 0000000000350ea0
> Call Trace:
> <TASK>
> inject_pending_event+0x2f7/0x4c0 [kvm]
> kvm_arch_vcpu_ioctl_run+0x791/0x17a0 [kvm]
> kvm_vcpu_ioctl+0x26d/0x650 [kvm]
> __x64_sys_ioctl+0x82/0xb0
> do_syscall_64+0x3b/0xc0
> entry_SYSCALL_64_after_hwframe+0x44/0xae
> </TASK>
>
> Fixes: 219b65dcf6c0 ("KVM: SVM: Improve nested interrupt injection")
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Maciej S. Szmigiero <maciej.szmigiero@xxxxxxxxxx>
> Co-developed-by: Sean Christopherson <seanjc@xxxxxxxxxx>
> Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
> ---
> arch/x86/kvm/svm/svm.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
> index 75b4f3ac8b1a..151fba0b405f 100644
> --- a/arch/x86/kvm/svm/svm.c
> +++ b/arch/x86/kvm/svm/svm.c
> @@ -3384,7 +3384,7 @@ static void svm_inject_irq(struct kvm_vcpu *vcpu)
> {
> struct vcpu_svm *svm = to_svm(vcpu);
>
> - BUG_ON(!(gif_set(svm)));
> + WARN_ON(!vcpu->arch.interrupt.soft && !gif_set(svm));
>
> trace_kvm_inj_virq(vcpu->arch.interrupt.nr);
> ++vcpu->stat.irq_injections;
