From: Paolo Bonzini <pbonzini@redhat.com>
To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Shannon Zhao <zhaoshenglong@huawei.com>,
qemu-devel@nongnu.org, qemu-arm@nongnu.org,
peter.maydell@linaro.org, christoffer.dall@linaro.org
Subject: Re: [Qemu-devel] [PATCH V2] virtio: Fix no interrupt when not creating msi controller
Date: Tue, 24 Jan 2017 10:25:00 +0100 [thread overview]
Message-ID: <5760ee8c-f567-0dfd-456f-65f8957b22e2@redhat.com> (raw)
In-Reply-To: <20170123190257-mutt-send-email-mst@kernel.org>
On 23/01/2017 18:04, Michael S. Tsirkin wrote:
>> For virtio-blk, my patch moved the setting of ISR from
>> virtio_queue_guest_notifier_read to virtio_notify_irqfd. This is
>> because the irqfd emulation only needs to trigger the interrupt.
>> Setting the ISR should have been done elsewhere.
>>
>> Can vhost set ISR (I thought it couldn't)? If so, it seems like ARM was
>> relying on QEMU's irqfd emulation, as a work around for vhost not
>> setting ISR. But this only works if irqfd is directed to QEMU and not
>> to KVM. So if vhost cannot set ISR, I think vhost should be disabled
>> unless MSI is active.
>>
>> Am I missing something?
>
> vhost doesn't set ISR ATM. Without MSI we are always bouncing
> interrupts through QEMU in particular in order to set ISR.
Where is the code that disables KVM irqfd?
Paolo
> Disabling vhost when user requested it was what we did
> at some point but this just confused people.
>
>
next prev parent reply other threads:[~2017-01-24 9:25 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-01-23 0:55 [Qemu-devel] [PATCH V2] virtio: Fix no interrupt when not creating msi controller Shannon Zhao
2017-01-23 16:07 ` Michael S. Tsirkin
2017-01-23 16:46 ` Paolo Bonzini
2017-01-23 17:04 ` Michael S. Tsirkin
2017-01-24 9:25 ` Paolo Bonzini [this message]
2017-01-24 14:44 ` Michael S. Tsirkin
2017-01-24 15:00 ` Paolo Bonzini
2017-01-24 15:05 ` Michael S. Tsirkin
2017-01-24 15:50 ` Paolo Bonzini
2017-01-24 15:55 ` Michael S. Tsirkin
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