Re: [PATCH v1 11/24] vfio-user: get region info

["Cédric Le Goater" <clg@redhat.com>]

On 11/9/22 00:13, John Johnson wrote:
> Add per-region FD to support mmap() of remote device regions
> 
> Signed-off-by: Elena Ufimtseva <elena.ufimtseva@oracle.com>
> Signed-off-by: John G Johnson <john.g.johnson@oracle.com>
> Signed-off-by: Jagannathan Raman <jag.raman@oracle.com>
> ---
>   hw/vfio/common.c              | 32 ++++++++++++++++++++---
>   hw/vfio/user-protocol.h       | 14 ++++++++++
>   hw/vfio/user.c                | 59 +++++++++++++++++++++++++++++++++++++++++++
>   include/hw/vfio/vfio-common.h |  8 +++---
>   4 files changed, 107 insertions(+), 6 deletions(-)
> 
> diff --git a/hw/vfio/common.c b/hw/vfio/common.c
> index c589bd9..87400b3 100644
> --- a/hw/vfio/common.c
> +++ b/hw/vfio/common.c
> @@ -41,6 +41,7 @@
>   #include "qapi/error.h"
>   #include "migration/migration.h"
>   #include "sysemu/tpm.h"
> +#include "hw/vfio/user.h"
>   
>   VFIOGroupList vfio_group_list =
>       QLIST_HEAD_INITIALIZER(vfio_group_list);
> @@ -1586,6 +1587,11 @@ int vfio_region_setup(Object *obj, VFIODevice *vbasedev, VFIORegion *region,
>       region->size = info->size;
>       region->fd_offset = info->offset;
>       region->nr = index;
> +    if (vbasedev->regfds != NULL) {
> +        region->fd = vbasedev->regfds[index];
> +    } else {
> +        region->fd = vbasedev->fd;
> +    }
>   
>       if (region->size) {
>           region->mem = g_new0(MemoryRegion, 1);
> @@ -1637,7 +1643,7 @@ int vfio_region_mmap(VFIORegion *region)
>   
>       for (i = 0; i < region->nr_mmaps; i++) {
>           region->mmaps[i].mmap = mmap(NULL, region->mmaps[i].size, prot,
> -                                     MAP_SHARED, region->vbasedev->fd,
> +                                     MAP_SHARED, region->fd,
>                                        region->fd_offset +
>                                        region->mmaps[i].offset);
>           if (region->mmaps[i].mmap == MAP_FAILED) {
> @@ -2442,10 +2448,17 @@ void vfio_put_base_device(VFIODevice *vbasedev)
>           int i;
>   
>           for (i = 0; i < vbasedev->num_regions; i++) {
> +            if (vbasedev->regfds != NULL && vbasedev->regfds[i] != -1) {
> +                close(vbasedev->regfds[i]);
> +            }
>               g_free(vbasedev->regions[i]);
>           }
>           g_free(vbasedev->regions);
>           vbasedev->regions = NULL;
> +        if (vbasedev->regfds != NULL) {
> +            g_free(vbasedev->regfds);
> +            vbasedev->regfds = NULL;
> +        }
>       }
>   
>       if (!vbasedev->group) {
> @@ -2461,12 +2474,16 @@ int vfio_get_region_info(VFIODevice *vbasedev, int index,
>                            struct vfio_region_info **info)
>   {
>       size_t argsz = sizeof(struct vfio_region_info);
> +    int fd = -1;
>       int ret;
>   
>       /* create region cache */
>       if (vbasedev->regions == NULL) {
>           vbasedev->regions = g_new0(struct vfio_region_info *,
>                                      vbasedev->num_regions);
> +        if (vbasedev->proxy != NULL) {

This looks like a shortcut. Could we introduce at least an inline helper
returning the need to allocate an fd per region ? It could use the same
kind of heuristic but it would be hidden under a helper.

> +            vbasedev->regfds = g_new0(int, vbasedev->num_regions);
> +        }
>       }
>       /* check cache */
>       if (vbasedev->regions[index] != NULL) {
> @@ -2480,7 +2497,7 @@ int vfio_get_region_info(VFIODevice *vbasedev, int index,
>   retry:
>       (*info)->argsz = argsz;
>   
> -    ret = VDEV_GET_REGION_INFO(vbasedev, *info);
> +    ret = VDEV_GET_REGION_INFO(vbasedev, *info, &fd);
>       if (ret != 0) {
>           g_free(*info);
>           *info = NULL;
> @@ -2490,12 +2507,19 @@ retry:
>       if ((*info)->argsz > argsz) {
>           argsz = (*info)->argsz;
>           *info = g_realloc(*info, argsz);
> +        if (fd != -1) {
> +            close(fd);
> +            fd = -1;
> +        }
>   
>           goto retry;
>       }
>   
>       /* fill cache */
>       vbasedev->regions[index] = *info;
> +    if (vbasedev->regfds != NULL) {
> +        vbasedev->regfds[index] = fd;
> +    }
>   
>       return 0;
>   }
> @@ -2655,10 +2679,12 @@ static int vfio_io_get_info(VFIODevice *vbasedev, struct vfio_device_info *info)
>   }
>   
>   static int vfio_io_get_region_info(VFIODevice *vbasedev,
> -                                   struct vfio_region_info *info)
> +                                   struct vfio_region_info *info,
> +                                   int *fd)
>   {
>       int ret;
>   
> +    *fd = -1;
>       ret = ioctl(vbasedev->fd, VFIO_DEVICE_GET_REGION_INFO, info);
>   
>       return ret < 0 ? -errno : ret;
> diff --git a/hw/vfio/user-protocol.h b/hw/vfio/user-protocol.h
> index 43912a5..a1b64fe 100644
> --- a/hw/vfio/user-protocol.h
> +++ b/hw/vfio/user-protocol.h
> @@ -126,4 +126,18 @@ typedef struct {
>       uint32_t cap_offset;
>   } VFIOUserDeviceInfo;
>   
> +/*
> + * VFIO_USER_DEVICE_GET_REGION_INFO
> + * imported from struct_vfio_region_info
> + */
> +typedef struct {
> +    VFIOUserHdr hdr;
> +    uint32_t argsz;
> +    uint32_t flags;
> +    uint32_t index;
> +    uint32_t cap_offset;
> +    uint64_t size;
> +    uint64_t offset;
> +} VFIOUserRegionInfo;
> +
>   #endif /* VFIO_USER_PROTOCOL_H */
> diff --git a/hw/vfio/user.c b/hw/vfio/user.c
> index 7873534..69b0fed 100644
> --- a/hw/vfio/user.c
> +++ b/hw/vfio/user.c
> @@ -1101,6 +1101,40 @@ static int vfio_user_get_info(VFIOProxy *proxy, struct vfio_device_info *info)
>       return 0;
>   }
>   
> +static int vfio_user_get_region_info(VFIOProxy *proxy,
> +                                     struct vfio_region_info *info,
> +                                     VFIOUserFDs *fds)
> +{
> +    g_autofree VFIOUserRegionInfo *msgp = NULL;
> +    uint32_t size;
> +
> +    /* data returned can be larger than vfio_region_info */
> +    if (info->argsz < sizeof(*info)) {
> +        error_printf("vfio_user_get_region_info argsz too small\n");

It would be nice to report the errors at the upper layer and remove all
the error_printf(). Since it seems too difficult in this case, may be
return -E2BIG.

Thanks,

C.

> +        return -EINVAL;
> +    }
> +    if (fds != NULL && fds->send_fds != 0) {
> +        error_printf("vfio_user_get_region_info can't send FDs\n");
> +        return -EINVAL;
> +    }
> +
> +    size = info->argsz + sizeof(VFIOUserHdr);
> +    msgp = g_malloc0(size);
> +
> +    vfio_user_request_msg(&msgp->hdr, VFIO_USER_DEVICE_GET_REGION_INFO,
> +                          sizeof(*msgp), 0);
> +    msgp->argsz = info->argsz;
> +    msgp->index = info->index;
> +
> +    vfio_user_send_wait(proxy, &msgp->hdr, fds, size, false);
> +    if (msgp->hdr.flags & VFIO_USER_ERROR) {
> +        return -msgp->hdr.error_reply;
> +    }
> +
> +    memcpy(info, &msgp->argsz, info->argsz);
> +    return 0;
> +}
> +
>   
>   /*
>    * Socket-based io_ops
> @@ -1126,7 +1160,32 @@ static int vfio_user_io_get_info(VFIODevice *vbasedev,
>       return 0;
>   }
>   
> +static int vfio_user_io_get_region_info(VFIODevice *vbasedev,
> +                                        struct vfio_region_info *info,
> +                                        int *fd)
> +{
> +    int ret;
> +    VFIOUserFDs fds = { 0, 1, fd};
> +
> +    ret = vfio_user_get_region_info(vbasedev->proxy, info, &fds);
> +    if (ret) {
> +        return ret;
> +    }
> +
> +    if (info->index > vbasedev->num_regions) {
> +        return -EINVAL;
> +    }
> +    /* cap_offset in valid area */
> +    if ((info->flags & VFIO_REGION_INFO_FLAG_CAPS) &&
> +        (info->cap_offset < sizeof(*info) || info->cap_offset > info->argsz)) {
> +        return -EINVAL;
> +    }
> +
> +    return 0;
> +}
> +
>   VFIODevIO vfio_dev_io_sock = {
>       .get_info = vfio_user_io_get_info,
> +    .get_region_info = vfio_user_io_get_region_info,
>   };
>   
> diff --git a/include/hw/vfio/vfio-common.h b/include/hw/vfio/vfio-common.h
> index fb7d865..3406e6a 100644
> --- a/include/hw/vfio/vfio-common.h
> +++ b/include/hw/vfio/vfio-common.h
> @@ -56,6 +56,7 @@ typedef struct VFIORegion {
>       uint32_t nr_mmaps;
>       VFIOMmap *mmaps;
>       uint8_t nr; /* cache the region number for debug */
> +    int fd; /* fd to mmap() region */
>   } VFIORegion;
>   
>   typedef struct VFIOMigration {
> @@ -150,6 +151,7 @@ typedef struct VFIODevice {
>       OnOffAuto pre_copy_dirty_page_tracking;
>       VFIOProxy *proxy;
>       struct vfio_region_info **regions;
> +    int *regfds;
>   } VFIODevice;
>   
>   struct VFIODeviceOps {
> @@ -172,7 +174,7 @@ struct VFIODeviceOps {
>   struct VFIODevIO {
>       int (*get_info)(VFIODevice *vdev, struct vfio_device_info *info);
>       int (*get_region_info)(VFIODevice *vdev,
> -                           struct vfio_region_info *info);
> +                           struct vfio_region_info *info, int *fd);
>       int (*get_irq_info)(VFIODevice *vdev, struct vfio_irq_info *irq);
>       int (*set_irqs)(VFIODevice *vdev, struct vfio_irq_set *irqs);
>       int (*region_read)(VFIODevice *vdev, uint8_t nr, off_t off, uint32_t size,
> @@ -183,8 +185,8 @@ struct VFIODevIO {
>   
>   #define VDEV_GET_INFO(vdev, info) \
>       ((vdev)->io_ops->get_info((vdev), (info)))
> -#define VDEV_GET_REGION_INFO(vdev, info) \
> -    ((vdev)->io_ops->get_region_info((vdev), (info)))
> +#define VDEV_GET_REGION_INFO(vdev, info, fd) \
> +    ((vdev)->io_ops->get_region_info((vdev), (info), (fd)))
>   #define VDEV_GET_IRQ_INFO(vdev, irq) \
>       ((vdev)->io_ops->get_irq_info((vdev), (irq)))
>   #define VDEV_SET_IRQS(vdev, irqs) \