linux-kernel - Re: [PATCH] virtio: uapi: Drop __packed attribute in linux/virtio

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Date: Wed, 24 Jan 2024 18:22:23 +0000
From: Jean-Philippe Brucker <jean-philippe@...aro.org>
To: Suzuki K Poulose <suzuki.poulose@....com>
Cc: linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
	Feng Liu <feliu@...dia.com>, "Michael S . Tsirkin" <mst@...hat.com>,
	Yishai Hadas <yishaih@...dia.com>,
	Alex Williamson <alex.williamson@...hat.com>
Subject: Re: [PATCH] virtio: uapi: Drop __packed attribute in
 linux/virtio_pci.h:

On Wed, Jan 24, 2024 at 05:23:45PM +0000, Suzuki K Poulose wrote:
> Commit 92792ac752aa ("virtio-pci: Introduce admin command sending function")
> added "__packed" structures to UAPI header linux/virtio_pci.h. This triggers
> build failures in the consumer userspace applications without proper "definition"
> of __packed (e.g., kvmtool build fails).
> 
> Moreover, the structures are already packed well, and doesn't need explicit
> packing, similar to the rest of the structures in all virtio_* headers. Remove
> the __packed attribute.
> 
> Fixes: commit 92792ac752aa ("virtio-pci: Introduce admin command sending function")
> Cc: Feng Liu <feliu@...dia.com>
> Cc: Michael S. Tsirkin <mst@...hat.com>
> Cc: Yishai Hadas <yishaih@...dia.com>
> Cc: Alex Williamson <alex.williamson@...hat.com>
> Cc: Jean-Philippe Brucker <jean-philippe@...aro.org>
> Signed-off-by: Suzuki K Poulose <suzuki.poulose@....com>

Reviewed-by: Jean-Philippe Brucker <jean-philippe@...aro.org>

> ---
>  include/uapi/linux/virtio_pci.h | 10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/include/uapi/linux/virtio_pci.h b/include/uapi/linux/virtio_pci.h
> index ef3810dee7ef..a8208492e822 100644
> --- a/include/uapi/linux/virtio_pci.h
> +++ b/include/uapi/linux/virtio_pci.h
> @@ -240,7 +240,7 @@ struct virtio_pci_cfg_cap {
>  #define VIRTIO_ADMIN_CMD_LEGACY_DEV_CFG_READ		0x5
>  #define VIRTIO_ADMIN_CMD_LEGACY_NOTIFY_INFO		0x6
>  
> -struct __packed virtio_admin_cmd_hdr {
> +struct virtio_admin_cmd_hdr {
>  	__le16 opcode;
>  	/*
>  	 * 1 - SR-IOV
> @@ -252,20 +252,20 @@ struct __packed virtio_admin_cmd_hdr {
>  	__le64 group_member_id;
>  };
>  
> -struct __packed virtio_admin_cmd_status {
> +struct virtio_admin_cmd_status {
>  	__le16 status;
>  	__le16 status_qualifier;
>  	/* Unused, reserved for future extensions. */
>  	__u8 reserved2[4];
>  };
>  
> -struct __packed virtio_admin_cmd_legacy_wr_data {
> +struct virtio_admin_cmd_legacy_wr_data {
>  	__u8 offset; /* Starting offset of the register(s) to write. */
>  	__u8 reserved[7];
>  	__u8 registers[];
>  };
>  
> -struct __packed virtio_admin_cmd_legacy_rd_data {
> +struct virtio_admin_cmd_legacy_rd_data {
>  	__u8 offset; /* Starting offset of the register(s) to read. */
>  };
>  
> @@ -275,7 +275,7 @@ struct __packed virtio_admin_cmd_legacy_rd_data {
>  
>  #define VIRTIO_ADMIN_CMD_MAX_NOTIFY_INFO 4
>  
> -struct __packed virtio_admin_cmd_notify_info_data {
> +struct virtio_admin_cmd_notify_info_data {
>  	__u8 flags; /* 0 = end of list, 1 = owner device, 2 = member device */
>  	__u8 bar; /* BAR of the member or the owner device */
>  	__u8 padding[6];
> -- 
> 2.34.1
>