Re: [PATCH V2 vfio 6/9] virtio-pci: Introduce APIs to execute legacy IO admin commands

[Yishai Hadas <yishaih@xxxxxxxxxx>]

On 31/10/2023 10:09, Michael S. Tsirkin wrote:
> On Sun, Oct 29, 2023 at 05:59:49PM +0200, Yishai Hadas wrote:
> > Introduce APIs to execute legacy IO admin commands.
> >
> > It includes: io_legacy_read/write for both common and the device
> > registers, io_legacy_notify_info.
> >
> > In addition, exposing an API to check whether the legacy IO commands are
> > supported. (i.e. virtio_pci_admin_has_legacy_io()).
> >
> > Those APIs will be used by the next patches from this series.
> >
> > Signed-off-by: Yishai Hadas <yishaih@xxxxxxxxxx>
> > ---
> >   drivers/virtio/virtio_pci_common.c |  11 ++
> >   drivers/virtio/virtio_pci_common.h |   2 +
> >   drivers/virtio/virtio_pci_modern.c | 241 +++++++++++++++++++++++++++++
> >   include/linux/virtio_pci_admin.h   |  21 +++
> >   4 files changed, 275 insertions(+)
> >   create mode 100644 include/linux/virtio_pci_admin.h
> >
> > diff --git a/drivers/virtio/virtio_pci_common.c b/drivers/virtio/virtio_pci_common.c
> > index 6b4766d5abe6..212d68401d2c 100644
> > --- a/drivers/virtio/virtio_pci_common.c
> > +++ b/drivers/virtio/virtio_pci_common.c
> > @@ -645,6 +645,17 @@ static struct pci_driver virtio_pci_driver = {
> >   	.sriov_configure = virtio_pci_sriov_configure,
> >   };
> >   
> > +struct virtio_device *virtio_pci_vf_get_pf_dev(struct pci_dev *pdev)
> > +{
> > +	struct virtio_pci_device *pf_vp_dev;
> > +
> > +	pf_vp_dev = pci_iov_get_pf_drvdata(pdev, &virtio_pci_driver);
> > +	if (IS_ERR(pf_vp_dev))
> > +		return NULL;
> > +
> > +	return &pf_vp_dev->vdev;
> > +}
> > +
> >   module_pci_driver(virtio_pci_driver);
> >   
> >   MODULE_AUTHOR("Anthony Liguori <aliguori@xxxxxxxxxx>");
> > diff --git a/drivers/virtio/virtio_pci_common.h b/drivers/virtio/virtio_pci_common.h
> > index 9e07e556a51a..07d4f863ac44 100644
> > --- a/drivers/virtio/virtio_pci_common.h
> > +++ b/drivers/virtio/virtio_pci_common.h
> > @@ -156,4 +156,6 @@ static inline void virtio_pci_legacy_remove(struct virtio_pci_device *vp_dev)
> >   int virtio_pci_modern_probe(struct virtio_pci_device *);
> >   void virtio_pci_modern_remove(struct virtio_pci_device *);
> >   
> > +struct virtio_device *virtio_pci_vf_get_pf_dev(struct pci_dev *pdev);
> > +
> >   #endif
> > diff --git a/drivers/virtio/virtio_pci_modern.c b/drivers/virtio/virtio_pci_modern.c
> > index 25e27aa79cab..def0f2de6091 100644
> > --- a/drivers/virtio/virtio_pci_modern.c
> > +++ b/drivers/virtio/virtio_pci_modern.c
> > @@ -15,6 +15,7 @@
> >    */
> >   
> >   #include <linux/delay.h>
> > +#include <linux/virtio_pci_admin.h>
> >   #define VIRTIO_PCI_NO_LEGACY
> >   #define VIRTIO_RING_NO_LEGACY
> >   #include "virtio_pci_common.h"
> > @@ -794,6 +795,246 @@ static void vp_modern_destroy_avq(struct virtio_device *vdev)
> >   	vp_dev->del_vq(&vp_dev->admin_vq.info);
> >   }
> >   
> > +#define VIRTIO_LEGACY_ADMIN_CMD_BITMAP \
> > +	(BIT_ULL(VIRTIO_ADMIN_CMD_LEGACY_COMMON_CFG_WRITE) | \
> > +	 BIT_ULL(VIRTIO_ADMIN_CMD_LEGACY_COMMON_CFG_READ) | \
> > +	 BIT_ULL(VIRTIO_ADMIN_CMD_LEGACY_DEV_CFG_WRITE) | \
> > +	 BIT_ULL(VIRTIO_ADMIN_CMD_LEGACY_DEV_CFG_READ) | \
> > +	 BIT_ULL(VIRTIO_ADMIN_CMD_LEGACY_NOTIFY_INFO))
> > +
> > +/*
> > + * virtio_pci_admin_has_legacy_io - Checks whether the legacy IO
> > + * commands are supported
> > + * @dev: VF pci_dev
> > + *
> > + * Returns true on success.
> > + */
> > +bool virtio_pci_admin_has_legacy_io(struct pci_dev *pdev)
> > +{
> > +	struct virtio_device *virtio_dev = virtio_pci_vf_get_pf_dev(pdev);
> > +	struct virtio_pci_device *vp_dev;
> > +
> > +	if (!virtio_dev)
> > +		return false;
> > +
> > +	if (!virtio_has_feature(virtio_dev, VIRTIO_F_ADMIN_VQ))
> > +		return false;
> > +
> > +	vp_dev = to_vp_device(virtio_dev);
> > +
> > +	if ((vp_dev->admin_vq.supported_cmds & VIRTIO_LEGACY_ADMIN_CMD_BITMAP) ==
> > +		VIRTIO_LEGACY_ADMIN_CMD_BITMAP)
> > +		return true;
> > +	return false;
> > +}
> > +EXPORT_SYMBOL_GPL(virtio_pci_admin_has_legacy_io);
> > +
> > +static int virtio_pci_admin_legacy_io_write(struct pci_dev *pdev, u16 opcode,
> > +					    u8 offset, u8 size, u8 *buf)
> > +{
> > +	struct virtio_device *virtio_dev = virtio_pci_vf_get_pf_dev(pdev);
> > +	struct virtio_admin_cmd_legacy_wr_data *data;
> > +	struct virtio_admin_cmd cmd = {};
> > +	struct scatterlist data_sg;
> > +	int vf_id;
> > +	int ret;
> > +
> > +	if (!virtio_dev)
> > +		return -ENODEV;
> > +
> > +	vf_id = pci_iov_vf_id(pdev);
> > +	if (vf_id < 0)
> > +		return vf_id;
> > +
> > +	data = kzalloc(sizeof(*data) + size, GFP_KERNEL);
> > +	if (!data)
> > +		return -ENOMEM;
> > +
> > +	data->offset = offset;
> > +	memcpy(data->registers, buf, size);
> > +	sg_init_one(&data_sg, data, sizeof(*data) + size);
> > +	cmd.opcode = cpu_to_le16(opcode);
> > +	cmd.group_type = cpu_to_le16(VIRTIO_ADMIN_GROUP_TYPE_SRIOV);
> > +	cmd.group_member_id = cpu_to_le64(vf_id + 1);
> > +	cmd.data_sg = &data_sg;
> > +	ret = vp_modern_admin_cmd_exec(virtio_dev, &cmd);
> > +
> > +	kfree(data);
> > +	return ret;
> > +}
>
> > +
> > +/*
> > + * virtio_pci_admin_legacy_io_write_common - Write common legacy registers
> > + * of a member device
> > + * @dev: VF pci_dev
> > + * @offset: starting byte offset within the registers to write to
> > + * @size: size of the data to write
> > + * @buf: buffer which holds the data
> > + *
> > + * Returns 0 on success, or negative on failure.
> > + */
> > +int virtio_pci_admin_legacy_common_io_write(struct pci_dev *pdev, u8 offset,
> > +					    u8 size, u8 *buf)
> > +{
> > +	return virtio_pci_admin_legacy_io_write(pdev,
> > +					VIRTIO_ADMIN_CMD_LEGACY_COMMON_CFG_WRITE,
> > +					offset, size, buf);
> > +}
> > +EXPORT_SYMBOL_GPL(virtio_pci_admin_legacy_common_io_write);
> So consider this for example. You start with a PCI device of a VF.
> Any number of these will access a PF in parallel. No locking
> is taking place so admin vq can get corrupted.

Right

As you commented correctly on previous patch, virtqueue_add_sgs() needs 
to be protected by some lock.
This is true also for virtqueue_get_buf().

So as part of V3 we may add a lock as part of virtqueue_exec_admin_cmd() 
to serialize a given command on the PF.

> And further, is caller expected not to invoke several of these
> in parallel on the same device? If yes this needs to be
> documented. I don't see where does vfio enforce this if yes.
Please have a look at virtiovf_issue_legacy_rw_cmd() from patch #9.

It has a lock on its VF device to serialize access to the bar, it 
includes calling this API.

Yishai

>   
> > +
> > +/*
> > + * virtio_pci_admin_legacy_io_write_device - Write device legacy registers
> > + * of a member device
> > + * @dev: VF pci_dev
> > + * @offset: starting byte offset within the registers to write to
> > + * @size: size of the data to write
> > + * @buf: buffer which holds the data
> > + *
> > + * Returns 0 on success, or negative on failure.
> > + */
> > +int virtio_pci_admin_legacy_device_io_write(struct pci_dev *pdev, u8 offset,
> > +					    u8 size, u8 *buf)
> > +{
> > +	return virtio_pci_admin_legacy_io_write(pdev,
> > +					VIRTIO_ADMIN_CMD_LEGACY_DEV_CFG_WRITE,
> > +					offset, size, buf);
> > +}
> > +EXPORT_SYMBOL_GPL(virtio_pci_admin_legacy_device_io_write);
> > +
> > +static int virtio_pci_admin_legacy_io_read(struct pci_dev *pdev, u16 opcode,
> > +					   u8 offset, u8 size, u8 *buf)
> > +{
> > +	struct virtio_device *virtio_dev = virtio_pci_vf_get_pf_dev(pdev);
> > +	struct virtio_admin_cmd_legacy_rd_data *data;
> > +	struct scatterlist data_sg, result_sg;
> > +	struct virtio_admin_cmd cmd = {};
> > +	int vf_id;
> > +	int ret;
> > +
> > +	if (!virtio_dev)
> > +		return -ENODEV;
> > +
> > +	vf_id = pci_iov_vf_id(pdev);
> > +	if (vf_id < 0)
> > +		return vf_id;
> > +
> > +	data = kzalloc(sizeof(*data), GFP_KERNEL);
> > +	if (!data)
> > +		return -ENOMEM;
> > +
> > +	data->offset = offset;
> > +	sg_init_one(&data_sg, data, sizeof(*data));
> > +	sg_init_one(&result_sg, buf, size);
> > +	cmd.opcode = cpu_to_le16(opcode);
> > +	cmd.group_type = cpu_to_le16(VIRTIO_ADMIN_GROUP_TYPE_SRIOV);
> > +	cmd.group_member_id = cpu_to_le64(vf_id + 1);
> > +	cmd.data_sg = &data_sg;
> > +	cmd.result_sg = &result_sg;
> > +	ret = vp_modern_admin_cmd_exec(virtio_dev, &cmd);
> > +
> > +	kfree(data);
> > +	return ret;
> > +}
> > +
> > +/*
> > + * virtio_pci_admin_legacy_device_io_read - Read legacy device registers of
> > + * a member device
> > + * @dev: VF pci_dev
> > + * @offset: starting byte offset within the registers to read from
> > + * @size: size of the data to be read
> > + * @buf: buffer to hold the returned data
> > + *
> > + * Returns 0 on success, or negative on failure.
> > + */
> > +int virtio_pci_admin_legacy_device_io_read(struct pci_dev *pdev, u8 offset,
> > +					   u8 size, u8 *buf)
> > +{
> > +	return virtio_pci_admin_legacy_io_read(pdev,
> > +					VIRTIO_ADMIN_CMD_LEGACY_COMMON_CFG_READ,
> > +					offset, size, buf);
> > +}
> > +EXPORT_SYMBOL_GPL(virtio_pci_admin_legacy_device_io_read);
> > +
> > +/*
> > + * virtio_pci_admin_legacy_common_io_read - Read legacy common registers of
> > + * a member device
> > + * @dev: VF pci_dev
> > + * @offset: starting byte offset within the registers to read from
> > + * @size: size of the data to be read
> > + * @buf: buffer to hold the returned data
> > + *
> > + * Returns 0 on success, or negative on failure.
> > + */
> > +int virtio_pci_admin_legacy_common_io_read(struct pci_dev *pdev, u8 offset,
> > +					    u8 size, u8 *buf)
> > +{
> > +	return virtio_pci_admin_legacy_io_read(pdev,
> > +					VIRTIO_ADMIN_CMD_LEGACY_COMMON_CFG_READ,
> > +					offset, size, buf);
> > +}
> > +EXPORT_SYMBOL_GPL(virtio_pci_admin_legacy_common_io_read);
> > +
> > +/*
> > + * virtio_pci_admin_legacy_io_notify_info - Read the queue notification
> > + * information for legacy interface
> > + * @dev: VF pci_dev
> > + * @req_bar_flags: requested bar flags
> > + * @bar: on output the BAR number of the member device
> > + * @bar_offset: on output the offset within bar
> > + *
> > + * Returns 0 on success, or negative on failure.
> > + */
> > +int virtio_pci_admin_legacy_io_notify_info(struct pci_dev *pdev,
> > +					   u8 req_bar_flags, u8 *bar,
> > +					   u64 *bar_offset)
> > +{
> > +	struct virtio_device *virtio_dev = virtio_pci_vf_get_pf_dev(pdev);
> > +	struct virtio_admin_cmd_notify_info_result *result;
> > +	struct virtio_admin_cmd cmd = {};
> > +	struct scatterlist result_sg;
> > +	int vf_id;
> > +	int ret;
> > +
> > +	if (!virtio_dev)
> > +		return -ENODEV;
> > +
> > +	vf_id = pci_iov_vf_id(pdev);
> > +	if (vf_id < 0)
> > +		return vf_id;
> > +
> > +	result = kzalloc(sizeof(*result), GFP_KERNEL);
> > +	if (!result)
> > +		return -ENOMEM;
> > +
> > +	sg_init_one(&result_sg, result, sizeof(*result));
> > +	cmd.opcode = cpu_to_le16(VIRTIO_ADMIN_CMD_LEGACY_NOTIFY_INFO);
> > +	cmd.group_type = cpu_to_le16(VIRTIO_ADMIN_GROUP_TYPE_SRIOV);
> > +	cmd.group_member_id = cpu_to_le64(vf_id + 1);
> > +	cmd.result_sg = &result_sg;
> > +	ret = vp_modern_admin_cmd_exec(virtio_dev, &cmd);
> > +	if (!ret) {
> > +		struct virtio_admin_cmd_notify_info_data *entry;
> > +		int i;
> > +
> > +		ret = -ENOENT;
> > +		for (i = 0; i < VIRTIO_ADMIN_CMD_MAX_NOTIFY_INFO; i++) {
> > +			entry = &result->entries[i];
> > +			if (entry->flags == VIRTIO_ADMIN_CMD_NOTIFY_INFO_FLAGS_END)
> > +				break;
> > +			if (entry->flags != req_bar_flags)
> > +				continue;
> > +			*bar = entry->bar;
> > +			*bar_offset = le64_to_cpu(entry->offset);
> > +			ret = 0;
> > +			break;
> > +		}
> > +	}
> > +
> > +	kfree(result);
> > +	return ret;
> > +}
> > +EXPORT_SYMBOL_GPL(virtio_pci_admin_legacy_io_notify_info);
> > +
> >   static const struct virtio_config_ops virtio_pci_config_nodev_ops = {
> >   	.get		= NULL,
> >   	.set		= NULL,
> > diff --git a/include/linux/virtio_pci_admin.h b/include/linux/virtio_pci_admin.h
> > new file mode 100644
> > index 000000000000..446ced8cb050
> > --- /dev/null
> > +++ b/include/linux/virtio_pci_admin.h
> > @@ -0,0 +1,21 @@
> > +/* SPDX-License-Identifier: GPL-2.0 */
> > +#ifndef _LINUX_VIRTIO_PCI_ADMIN_H
> > +#define _LINUX_VIRTIO_PCI_ADMIN_H
> > +
> > +#include <linux/types.h>
> > +#include <linux/pci.h>
> > +
> > +bool virtio_pci_admin_has_legacy_io(struct pci_dev *pdev);
> > +int virtio_pci_admin_legacy_common_io_write(struct pci_dev *pdev, u8 offset,
> > +					    u8 size, u8 *buf);
> > +int virtio_pci_admin_legacy_common_io_read(struct pci_dev *pdev, u8 offset,
> > +					   u8 size, u8 *buf);
> > +int virtio_pci_admin_legacy_device_io_write(struct pci_dev *pdev, u8 offset,
> > +					    u8 size, u8 *buf);
> > +int virtio_pci_admin_legacy_device_io_read(struct pci_dev *pdev, u8 offset,
> > +					   u8 size, u8 *buf);
> > +int virtio_pci_admin_legacy_io_notify_info(struct pci_dev *pdev,
> > +					   u8 req_bar_flags, u8 *bar,
> > +					   u64 *bar_offset);
> > +
> > +#endif /* _LINUX_VIRTIO_PCI_ADMIN_H */
> > --
> > 2.27.0