Re: [PATCH v3 01/17] virtio_pci: struct virtio_pci_common_cfg add queue_notify_data

On Tue, Feb 8, 2022 at 10:17 AM Xuan Zhuo [off-list ref] wrote:

On Mon, 7 Feb 2022 16:06:15 +0800, Jason Wang [off-list ref] wrote:

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On Mon, Feb 7, 2022 at 2:07 PM Xuan Zhuo [off-list ref] wrote:

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On Mon, 7 Feb 2022 11:41:06 +0800, Jason Wang [off-list ref] wrote:

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在 2022/1/26 下午3:35, Xuan Zhuo 写道:

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Add queue_notify_data in struct virtio_pci_common_cfg, which comes from
here https://github.com/oasis-tcs/virtio-spec/issues/89

Since I want to add queue_reset after it, I submitted this patch first.

Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
---
  include/uapi/linux/virtio_pci.h | 1 +
  1 file changed, 1 insertion(+)

diff --git a/include/uapi/linux/virtio_pci.h b/include/uapi/linux/virtio_pci.h
index 3a86f36d7e3d..492c89f56c6a 100644
--- a/include/uapi/linux/virtio_pci.h
+++ b/include/uapi/linux/virtio_pci.h

@@ -164,6 +164,7 @@ struct virtio_pci_common_cfg {
    __le32 queue_avail_hi;          /* read-write */
    __le32 queue_used_lo;           /* read-write */
    __le32 queue_used_hi;           /* read-write */
+   __le16 queue_notify_data;       /* read-write */
  };

So I had the same concern as previous version.

This breaks uABI where program may try to use sizeof(struct
virtio_pci_common_cfg).

We probably need a container structure here.

I see, I plan to add a struct like this, do you think it's appropriate?

struct virtio_pci_common_cfg_v1 {
        struct virtio_pci_common_cfg cfg;
        __le16 queue_notify_data;       /* read-write */
}

Something like this but we probably need a better name.

how about this?

        /* Ext Fields in VIRTIO_PCI_CAP_COMMON_CFG: */
        struct virtio_pci_common_cfg_ext {
                struct virtio_pci_common_cfg cfg;

                __le16 queue_notify_data;       /* read-write */

                __le16 reserved0;
                __le16 reserved1;
                __le16 reserved2;
                __le16 reserved3;
                __le16 reserved4;
                __le16 reserved5;
                __le16 reserved6;
                __le16 reserved7;
                __le16 reserved8;
                __le16 reserved9;
                __le16 reserved10;
                __le16 reserved11;
                __le16 reserved12;
                __le16 reserved13;
                __le16 reserved14;
        };

I still think the container without padding is better. Otherwise
userspace needs to use offset_of() trick instead of sizeof().

Thanks

Thanks

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Thanks

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Thanks.

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THanks

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  /* Fields in VIRTIO_PCI_CAP_PCI_CFG: */