Michael S. Tsirkin
2022-Jun-28 06:10 UTC
[PATCH v10 25/41] virtio_pci: struct virtio_pci_common_cfg add queue_notify_data
On Tue, Jun 28, 2022 at 02:07:28PM +0800, Jason Wang wrote:> On Tue, Jun 28, 2022 at 1:46 PM Michael S. Tsirkin <mst at redhat.com> wrote: > > > > On Tue, Jun 28, 2022 at 11:50:37AM +0800, Jason Wang wrote: > > > On Mon, Jun 27, 2022 at 7:53 PM Michael S. Tsirkin <mst at redhat.com> wrote: > > > > > > > > On Mon, Jun 27, 2022 at 04:14:20PM +0800, Jason Wang wrote: > > > > > On Mon, Jun 27, 2022 at 3:58 PM Michael S. Tsirkin <mst at redhat.com> wrote: > > > > > > > > > > > > On Mon, Jun 27, 2022 at 03:45:30PM +0800, Jason Wang wrote: > > > > > > > On Mon, Jun 27, 2022 at 2:39 PM Michael S. Tsirkin <mst at redhat.com> wrote: > > > > > > > > > > > > > > > > On Mon, Jun 27, 2022 at 10:30:42AM +0800, Jason Wang wrote: > > > > > > > > > On Fri, Jun 24, 2022 at 2:59 PM Michael S. Tsirkin <mst at redhat.com> wrote: > > > > > > > > > > > > > > > > > > > > On Fri, Jun 24, 2022 at 10:56:05AM +0800, Xuan Zhuo wrote: > > > > > > > > > > > Add queue_notify_data in struct virtio_pci_common_cfg, which comes from > > > > > > > > > > > here https://github.com/oasis-tcs/virtio-spec/issues/89 > > > > > > > > > > > > > > > > > > > > > > For not breaks uABI, add a new struct virtio_pci_common_cfg_notify. > > > > > > > > > > > > > > > > > > > > What exactly is meant by not breaking uABI? > > > > > > > > > > Users are supposed to be prepared for struct size to change ... no? > > > > > > > > > > > > > > > > > > Not sure, any doc for this? > > > > > > > > > > > > > > > > > > Thanks > > > > > > > > > > > > > > > > > > > > > > > > Well we have this: > > > > > > > > > > > > > > > > The drivers SHOULD only map part of configuration structure > > > > > > > > large enough for device operation. The drivers MUST handle > > > > > > > > an unexpectedly large \field{length}, but MAY check that \field{length} > > > > > > > > is large enough for device operation. > > > > > > > > > > > > > > Yes, but that's the device/driver interface. What's done here is the > > > > > > > userspace/kernel. > > > > > > > > > > > > > > Userspace may break if it uses e.g sizeof(struct virtio_pci_common_cfg)? > > > > > > > > > > > > > > Thanks > > > > > > > > > > > > Hmm I guess there's risk... but then how are we going to maintain this > > > > > > going forward? Add a new struct on any change? > > > > > > > > > > This is the way we have used it for the past 5 or more years. I don't > > > > > see why this must be handled in the vq reset feature. > > > > > > > > > > >Can we at least > > > > > > prevent this going forward somehow? > > > > > > > > > > Like have some padding? > > > > > > > > > > Thanks > > > > > > > > Maybe - this is what QEMU does ... > > > > > > Do you want this to be addressed in this series (it's already very huge anyhow)? > > > > > > Thanks > > > > Let's come up with a solution at least. QEMU does not seem to need the struct. > > If we want to implement it in Qemu we need that: > > https://github.com/fengidri/qemu/commit/39b79335cb55144d11a3b01f93d46cc73342c6bb > > > Let's just put > > it in virtio_pci_modern.h for now then? > > Does this mean userspace needs to define the struct by their own > instead of depending on the uapi in the future? > > Thanks$ git grep 'struct virtio_pci_common_cfg' include/standard-headers/linux/virtio_pci.h:struct virtio_pci_common_cfg { tests/qtest/libqos/virtio-pci-modern.c: offsetof(struct virtio_pci_common_cfg, tests/qtest/libqos/virtio-pci-modern.c: offsetof(struct virtio_pci_common_cfg, device_feature)); tests/qtest/libqos/virtio-pci-modern.c: offsetof(struct virtio_pci_common_cfg, tests/qtest/libqos/virtio-pci-modern.c: offsetof(struct virtio_pci_common_cfg, device_feature)); tests/qtest/libqos/virtio-pci-modern.c: offsetof(struct virtio_pci_common_cfg, tests/qtest/libqos/virtio-pci-modern.c: offsetof(struct virtio_pci_common_cfg, tests/qtest/libqos/virtio-pci-modern.c: offsetof(struct virtio_pci_common_cfg, tests/qtest/libqos/virtio-pci-modern.c: offsetof(struct virtio_pci_common_cfg, tests/qtest/libqos/virtio-pci-modern.c: offsetof(struct virtio_pci_common_cfg, tests/qtest/libqos/virtio-pci-modern.c: offsetof(struct virtio_pci_common_cfg, guest_feature)); tests/qtest/libqos/virtio-pci-modern.c: offsetof(struct virtio_pci_common_cfg, tests/qtest/libqos/virtio-pci-modern.c: offsetof(struct virtio_pci_common_cfg, guest_feature)); tests/qtest/libqos/virtio-pci-modern.c: offsetof(struct virtio_pci_common_cfg, tests/qtest/libqos/virtio-pci-modern.c: offsetof(struct virtio_pci_common_cfg, tests/qtest/libqos/virtio-pci-modern.c: offsetof(struct virtio_pci_common_cfg, queue_select), tests/qtest/libqos/virtio-pci-modern.c: offsetof(struct virtio_pci_common_cfg, queue_size)); tests/qtest/libqos/virtio-pci-modern.c: offsetof(struct virtio_pci_common_cfg, queue_desc_lo), tests/qtest/libqos/virtio-pci-modern.c: offsetof(struct virtio_pci_common_cfg, queue_desc_hi), tests/qtest/libqos/virtio-pci-modern.c: offsetof(struct virtio_pci_common_cfg, queue_avail_lo), tests/qtest/libqos/virtio-pci-modern.c: offsetof(struct virtio_pci_common_cfg, queue_avail_hi), tests/qtest/libqos/virtio-pci-modern.c: offsetof(struct virtio_pci_common_cfg, queue_used_lo), tests/qtest/libqos/virtio-pci-modern.c: offsetof(struct virtio_pci_common_cfg, queue_used_hi), tests/qtest/libqos/virtio-pci-modern.c: offsetof(struct virtio_pci_common_cfg, tests/qtest/libqos/virtio-pci-modern.c: offsetof(struct virtio_pci_common_cfg, queue_enable), 1); tests/qtest/libqos/virtio-pci-modern.c: offsetof(struct virtio_pci_common_cfg, msix_config), entry); tests/qtest/libqos/virtio-pci-modern.c: offsetof(struct virtio_pci_common_cfg, tests/qtest/libqos/virtio-pci-modern.c: offsetof(struct virtio_pci_common_cfg, queue_msix_vector), tests/qtest/libqos/virtio-pci-modern.c: offsetof(struct virtio_pci_common_cfg, The only user of the struct is libqos and it just wants the offsets so can use macros just as well.> > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > Since I want to add queue_reset after queue_notify_data, I submitted > > > > > > > > > > > this patch first. > > > > > > > > > > > > > > > > > > > > > > Signed-off-by: Xuan Zhuo <xuanzhuo at linux.alibaba.com> > > > > > > > > > > > Acked-by: Jason Wang <jasowang at redhat.com> > > > > > > > > > > > --- > > > > > > > > > > > include/uapi/linux/virtio_pci.h | 7 +++++++ > > > > > > > > > > > 1 file changed, 7 insertions(+) > > > > > > > > > > > > > > > > > > > > > > diff --git a/include/uapi/linux/virtio_pci.h b/include/uapi/linux/virtio_pci.h > > > > > > > > > > > index 3a86f36d7e3d..22bec9bd0dfc 100644 > > > > > > > > > > > --- a/include/uapi/linux/virtio_pci.h > > > > > > > > > > > +++ b/include/uapi/linux/virtio_pci.h > > > > > > > > > > > @@ -166,6 +166,13 @@ struct virtio_pci_common_cfg { > > > > > > > > > > > __le32 queue_used_hi; /* read-write */ > > > > > > > > > > > }; > > > > > > > > > > > > > > > > > > > > > > +struct virtio_pci_common_cfg_notify { > > > > > > > > > > > + struct virtio_pci_common_cfg cfg; > > > > > > > > > > > + > > > > > > > > > > > + __le16 queue_notify_data; /* read-write */ > > > > > > > > > > > + __le16 padding; > > > > > > > > > > > +}; > > > > > > > > > > > + > > > > > > > > > > > /* Fields in VIRTIO_PCI_CAP_PCI_CFG: */ > > > > > > > > > > > struct virtio_pci_cfg_cap { > > > > > > > > > > > struct virtio_pci_cap cap; > > > > > > > > > > > -- > > > > > > > > > > > 2.31.0 > > > > > > > > > > > > > > > > > > > > > > > > > > > > > >
Jason Wang
2022-Jun-28 06:12 UTC
[PATCH v10 25/41] virtio_pci: struct virtio_pci_common_cfg add queue_notify_data
On Tue, Jun 28, 2022 at 2:10 PM Michael S. Tsirkin <mst at redhat.com> wrote:> > On Tue, Jun 28, 2022 at 02:07:28PM +0800, Jason Wang wrote: > > On Tue, Jun 28, 2022 at 1:46 PM Michael S. Tsirkin <mst at redhat.com> wrote: > > > > > > On Tue, Jun 28, 2022 at 11:50:37AM +0800, Jason Wang wrote: > > > > On Mon, Jun 27, 2022 at 7:53 PM Michael S. Tsirkin <mst at redhat.com> wrote: > > > > > > > > > > On Mon, Jun 27, 2022 at 04:14:20PM +0800, Jason Wang wrote: > > > > > > On Mon, Jun 27, 2022 at 3:58 PM Michael S. Tsirkin <mst at redhat.com> wrote: > > > > > > > > > > > > > > On Mon, Jun 27, 2022 at 03:45:30PM +0800, Jason Wang wrote: > > > > > > > > On Mon, Jun 27, 2022 at 2:39 PM Michael S. Tsirkin <mst at redhat.com> wrote: > > > > > > > > > > > > > > > > > > On Mon, Jun 27, 2022 at 10:30:42AM +0800, Jason Wang wrote: > > > > > > > > > > On Fri, Jun 24, 2022 at 2:59 PM Michael S. Tsirkin <mst at redhat.com> wrote: > > > > > > > > > > > > > > > > > > > > > > On Fri, Jun 24, 2022 at 10:56:05AM +0800, Xuan Zhuo wrote: > > > > > > > > > > > > Add queue_notify_data in struct virtio_pci_common_cfg, which comes from > > > > > > > > > > > > here https://github.com/oasis-tcs/virtio-spec/issues/89 > > > > > > > > > > > > > > > > > > > > > > > > For not breaks uABI, add a new struct virtio_pci_common_cfg_notify. > > > > > > > > > > > > > > > > > > > > > > What exactly is meant by not breaking uABI? > > > > > > > > > > > Users are supposed to be prepared for struct size to change ... no? > > > > > > > > > > > > > > > > > > > > Not sure, any doc for this? > > > > > > > > > > > > > > > > > > > > Thanks > > > > > > > > > > > > > > > > > > > > > > > > > > > Well we have this: > > > > > > > > > > > > > > > > > > The drivers SHOULD only map part of configuration structure > > > > > > > > > large enough for device operation. The drivers MUST handle > > > > > > > > > an unexpectedly large \field{length}, but MAY check that \field{length} > > > > > > > > > is large enough for device operation. > > > > > > > > > > > > > > > > Yes, but that's the device/driver interface. What's done here is the > > > > > > > > userspace/kernel. > > > > > > > > > > > > > > > > Userspace may break if it uses e.g sizeof(struct virtio_pci_common_cfg)? > > > > > > > > > > > > > > > > Thanks > > > > > > > > > > > > > > Hmm I guess there's risk... but then how are we going to maintain this > > > > > > > going forward? Add a new struct on any change? > > > > > > > > > > > > This is the way we have used it for the past 5 or more years. I don't > > > > > > see why this must be handled in the vq reset feature. > > > > > > > > > > > > >Can we at least > > > > > > > prevent this going forward somehow? > > > > > > > > > > > > Like have some padding? > > > > > > > > > > > > Thanks > > > > > > > > > > Maybe - this is what QEMU does ... > > > > > > > > Do you want this to be addressed in this series (it's already very huge anyhow)? > > > > > > > > Thanks > > > > > > Let's come up with a solution at least. QEMU does not seem to need the struct. > > > > If we want to implement it in Qemu we need that: > > > > https://github.com/fengidri/qemu/commit/39b79335cb55144d11a3b01f93d46cc73342c6bb > > > > > Let's just put > > > it in virtio_pci_modern.h for now then? > > > > Does this mean userspace needs to define the struct by their own > > instead of depending on the uapi in the future? > > > > Thanks > > > $ git grep 'struct virtio_pci_common_cfg' > include/standard-headers/linux/virtio_pci.h:struct virtio_pci_common_cfg { > tests/qtest/libqos/virtio-pci-modern.c: offsetof(struct virtio_pci_common_cfg, > tests/qtest/libqos/virtio-pci-modern.c: offsetof(struct virtio_pci_common_cfg, device_feature)); > tests/qtest/libqos/virtio-pci-modern.c: offsetof(struct virtio_pci_common_cfg, > tests/qtest/libqos/virtio-pci-modern.c: offsetof(struct virtio_pci_common_cfg, device_feature)); > tests/qtest/libqos/virtio-pci-modern.c: offsetof(struct virtio_pci_common_cfg, > tests/qtest/libqos/virtio-pci-modern.c: offsetof(struct virtio_pci_common_cfg, > tests/qtest/libqos/virtio-pci-modern.c: offsetof(struct virtio_pci_common_cfg, > tests/qtest/libqos/virtio-pci-modern.c: offsetof(struct virtio_pci_common_cfg, > tests/qtest/libqos/virtio-pci-modern.c: offsetof(struct virtio_pci_common_cfg, > tests/qtest/libqos/virtio-pci-modern.c: offsetof(struct virtio_pci_common_cfg, guest_feature)); > tests/qtest/libqos/virtio-pci-modern.c: offsetof(struct virtio_pci_common_cfg, > tests/qtest/libqos/virtio-pci-modern.c: offsetof(struct virtio_pci_common_cfg, guest_feature)); > tests/qtest/libqos/virtio-pci-modern.c: offsetof(struct virtio_pci_common_cfg, > tests/qtest/libqos/virtio-pci-modern.c: offsetof(struct virtio_pci_common_cfg, > tests/qtest/libqos/virtio-pci-modern.c: offsetof(struct virtio_pci_common_cfg, queue_select), > tests/qtest/libqos/virtio-pci-modern.c: offsetof(struct virtio_pci_common_cfg, queue_size)); > tests/qtest/libqos/virtio-pci-modern.c: offsetof(struct virtio_pci_common_cfg, queue_desc_lo), > tests/qtest/libqos/virtio-pci-modern.c: offsetof(struct virtio_pci_common_cfg, queue_desc_hi), > tests/qtest/libqos/virtio-pci-modern.c: offsetof(struct virtio_pci_common_cfg, queue_avail_lo), > tests/qtest/libqos/virtio-pci-modern.c: offsetof(struct virtio_pci_common_cfg, queue_avail_hi), > tests/qtest/libqos/virtio-pci-modern.c: offsetof(struct virtio_pci_common_cfg, queue_used_lo), > tests/qtest/libqos/virtio-pci-modern.c: offsetof(struct virtio_pci_common_cfg, queue_used_hi), > tests/qtest/libqos/virtio-pci-modern.c: offsetof(struct virtio_pci_common_cfg, > tests/qtest/libqos/virtio-pci-modern.c: offsetof(struct virtio_pci_common_cfg, queue_enable), 1); > tests/qtest/libqos/virtio-pci-modern.c: offsetof(struct virtio_pci_common_cfg, msix_config), entry); > tests/qtest/libqos/virtio-pci-modern.c: offsetof(struct virtio_pci_common_cfg, > tests/qtest/libqos/virtio-pci-modern.c: offsetof(struct virtio_pci_common_cfg, queue_msix_vector), > tests/qtest/libqos/virtio-pci-modern.c: offsetof(struct virtio_pci_common_cfg, > > > The only user of the struct is libqos and it just wants > the offsets so can use macros just as well.Yes, so this way should be fine. Thanks> > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > Since I want to add queue_reset after queue_notify_data, I submitted > > > > > > > > > > > > this patch first. > > > > > > > > > > > > > > > > > > > > > > > > Signed-off-by: Xuan Zhuo <xuanzhuo at linux.alibaba.com> > > > > > > > > > > > > Acked-by: Jason Wang <jasowang at redhat.com> > > > > > > > > > > > > --- > > > > > > > > > > > > include/uapi/linux/virtio_pci.h | 7 +++++++ > > > > > > > > > > > > 1 file changed, 7 insertions(+) > > > > > > > > > > > > > > > > > > > > > > > > diff --git a/include/uapi/linux/virtio_pci.h b/include/uapi/linux/virtio_pci.h > > > > > > > > > > > > index 3a86f36d7e3d..22bec9bd0dfc 100644 > > > > > > > > > > > > --- a/include/uapi/linux/virtio_pci.h > > > > > > > > > > > > +++ b/include/uapi/linux/virtio_pci.h > > > > > > > > > > > > @@ -166,6 +166,13 @@ struct virtio_pci_common_cfg { > > > > > > > > > > > > __le32 queue_used_hi; /* read-write */ > > > > > > > > > > > > }; > > > > > > > > > > > > > > > > > > > > > > > > +struct virtio_pci_common_cfg_notify { > > > > > > > > > > > > + struct virtio_pci_common_cfg cfg; > > > > > > > > > > > > + > > > > > > > > > > > > + __le16 queue_notify_data; /* read-write */ > > > > > > > > > > > > + __le16 padding; > > > > > > > > > > > > +}; > > > > > > > > > > > > + > > > > > > > > > > > > /* Fields in VIRTIO_PCI_CAP_PCI_CFG: */ > > > > > > > > > > > > struct virtio_pci_cfg_cap { > > > > > > > > > > > > struct virtio_pci_cap cap; > > > > > > > > > > > > -- > > > > > > > > > > > > 2.31.0 > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > >