Re: [Qemu-devel] [virtio-dev] RE: [PATCH v3 6/6] vhost-user: support registering external host notifiers

> -Original Message- > From: Michael S. Tsirkin [mailto:m...@redhat.com] > Sent: Friday, April 20, 2018 12:56 AM > To: Liang, Cunming > Cc: Paolo Bonzini ; Bie, Tiwei ; > jasow...@redhat.com; alex.william...@redhat.com;

Re: [Qemu-devel] [virtio-dev] RE: [PATCH v3 6/6] vhost-user: support registering external host notifiers

On Thu, Apr 19, 2018 at 07:35:57PM +0200, Paolo Bonzini wrote: > On 19/04/2018 19:27, Michael S. Tsirkin wrote: > > > > That CONFIG_SMP here is clearly wrong but I don't really know what > > to set it to. Also, we probably should switch virtio_wmb to dma_XX > > barriers. > > > > That's actually

Re: [Qemu-devel] [virtio-dev] RE: [PATCH v3 6/6] vhost-user: support registering external host notifiers

On 19/04/2018 19:27, Michael S. Tsirkin wrote: > > That CONFIG_SMP here is clearly wrong but I don't really know what > to set it to. Also, we probably should switch virtio_wmb to dma_XX > barriers. > > That's actually easy. Will try to do. Should it be dma_wmb() before updating the indices,

Re: [Qemu-devel] [virtio-dev] RE: [PATCH v3 6/6] vhost-user: support registering external host notifiers

On Thu, Apr 19, 2018 at 06:59:39PM +0200, Paolo Bonzini wrote: > On 19/04/2018 18:52, Liang, Cunming wrote: > >>> Oh you are right. > >>> > >>> So it's only needed for non-intel platforms or when packets are > >>> in WC memory then. And I don't know whether dpdk ever puts > >>> packets in WC

Re: [Qemu-devel] [virtio-dev] RE: [PATCH v3 6/6] vhost-user: support registering external host notifiers

On 19/04/2018 18:52, Liang, Cunming wrote: >>> Oh you are right. >>> >>> So it's only needed for non-intel platforms or when packets are >>> in WC memory then. And I don't know whether dpdk ever puts >>> packets in WC memory. >>> >>> I guess we'll cross this bridge when we get to it. >> Non-TSO

Re: [Qemu-devel] [virtio-dev] RE: [PATCH v3 6/6] vhost-user: support registering external host notifiers

On Thu, Apr 19, 2018 at 04:24:29PM +, Liang, Cunming wrote: > > > > -Original Message- > > From: Michael S. Tsirkin [mailto:m...@redhat.com] > > Sent: Thursday, April 19, 2018 11:19 PM > > To: Paolo Bonzini > > Cc: Liang, Cunming ; Bie,

Re: [Qemu-devel] [virtio-dev] RE: [PATCH v3 6/6] vhost-user: support registering external host notifiers

On Thu, Apr 19, 2018 at 06:07:07PM +0200, Paolo Bonzini wrote: > On 19/04/2018 17:59, Michael S. Tsirkin wrote: > > On Thu, Apr 19, 2018 at 05:51:51PM +0200, Paolo Bonzini wrote: > >> On 19/04/2018 17:19, Michael S. Tsirkin wrote: > - if we make it 1 when weak barriers are needed, the device

Re: [Qemu-devel] [virtio-dev] RE: [PATCH v3 6/6] vhost-user: support registering external host notifiers

> -Original Message- > From: Michael S. Tsirkin [mailto:m...@redhat.com] > Sent: Thursday, April 19, 2018 11:19 PM > To: Paolo Bonzini > Cc: Liang, Cunming ; Bie, Tiwei > ; > jasow...@redhat.com;

Re: [Qemu-devel] [virtio-dev] RE: [PATCH v3 6/6] vhost-user: support registering external host notifiers

On 19/04/2018 17:59, Michael S. Tsirkin wrote: > On Thu, Apr 19, 2018 at 05:51:51PM +0200, Paolo Bonzini wrote: >> On 19/04/2018 17:19, Michael S. Tsirkin wrote: - if we make it 1 when weak barriers are needed, the device also needs to nack feature negotiation (not allow setting the

Re: [Qemu-devel] [virtio-dev] RE: [PATCH v3 6/6] vhost-user: support registering external host notifiers

On Thu, Apr 19, 2018 at 05:51:51PM +0200, Paolo Bonzini wrote: > On 19/04/2018 17:19, Michael S. Tsirkin wrote: > >> - if we make it 1 when weak barriers are needed, the device also needs > >> to nack feature negotiation (not allow setting the FEATURES_OK) if the > >> bit is not set by the driver.

Re: [Qemu-devel] [virtio-dev] RE: [PATCH v3 6/6] vhost-user: support registering external host notifiers

On 19/04/2018 17:19, Michael S. Tsirkin wrote: >> - if we make it 1 when weak barriers are needed, the device also needs >> to nack feature negotiation (not allow setting the FEATURES_OK) if the >> bit is not set by the driver. >> However, that is not enough. Live >> migration assumes that it is

Re: [Qemu-devel] [virtio-dev] RE: [PATCH v3 6/6] vhost-user: support registering external host notifiers

On Thu, Apr 19, 2018 at 03:02:40PM +0200, Paolo Bonzini wrote: > On 19/04/2018 14:43, Liang, Cunming wrote: > >> 2. Memory barriers. Right now after updating the avail idx, > >> virtio does smp_wmb() and then the MMIO write. Normal hardware > >> drivers do wmb() which is an sfence. Can a PCI

Re: [Qemu-devel] [virtio-dev] RE: [PATCH v3 6/6] vhost-user: support registering external host notifiers

On 19/04/2018 14:43, Liang, Cunming wrote: >> 2. Memory barriers. Right now after updating the avail idx, >> virtio does smp_wmb() and then the MMIO write. Normal hardware >> drivers do wmb() which is an sfence. Can a PCI device read bypass >> index write and see a stale index value? > > A