From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:36941) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cVxLk-0002Co-DR for qemu-devel@nongnu.org; Tue, 24 Jan 2017 04:25:13 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1cVxLj-0005Br-KV for qemu-devel@nongnu.org; Tue, 24 Jan 2017 04:25:12 -0500 References: <1485132904-17632-1-git-send-email-zhaoshenglong@huawei.com> <20170123180247-mutt-send-email-mst@kernel.org> <49fcc1e0-f439-9212-25f1-9b8dce6462cc@redhat.com> <20170123190257-mutt-send-email-mst@kernel.org> From: Paolo Bonzini Message-ID: <5760ee8c-f567-0dfd-456f-65f8957b22e2@redhat.com> Date: Tue, 24 Jan 2017 10:25:00 +0100 MIME-Version: 1.0 In-Reply-To: <20170123190257-mutt-send-email-mst@kernel.org> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH V2] virtio: Fix no interrupt when not creating msi controller List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Michael S. Tsirkin" Cc: Shannon Zhao , qemu-devel@nongnu.org, qemu-arm@nongnu.org, peter.maydell@linaro.org, christoffer.dall@linaro.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. > >