Re: [PATCH RFC server 06/11] vfio-user: handle PCI config space accesses

[John Levon]

On Mon, Jul 19, 2021 at 04:00:08PM -0400, Jagannathan Raman wrote:

> Define and register handlers for PCI config space accesses
> 
> 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/remote/vfio-user-obj.c | 41 +++++++++++++++++++++++++++++++++++++++++
>  hw/remote/trace-events    |  2 ++
>  2 files changed, 43 insertions(+)
> 
> diff --git a/hw/remote/vfio-user-obj.c b/hw/remote/vfio-user-obj.c
> index 6a2d0f5..60d9fa8 100644
> --- a/hw/remote/vfio-user-obj.c
> +++ b/hw/remote/vfio-user-obj.c
> @@ -36,6 +36,7 @@
>  #include "sysemu/runstate.h"
>  #include "qemu/notify.h"
>  #include "qemu/thread.h"
> +#include "qemu/main-loop.h"
>  #include "qapi/error.h"
>  #include "sysemu/sysemu.h"
>  #include "hw/qdev-core.h"
> @@ -131,6 +132,35 @@ static void *vfu_object_ctx_run(void *opaque)
>      return NULL;
>  }
>  
> +static ssize_t vfu_object_cfg_access(vfu_ctx_t *vfu_ctx, char * const buf,
> +                                     size_t count, loff_t offset,
> +                                     const bool is_write)
> +{
> +    VfuObject *o = vfu_get_private(vfu_ctx);
> +    uint32_t val = 0;
> +    int i;
> +
> +    qemu_mutex_lock_iothread();
> +
> +    for (i = 0; i < count; i++) {
> +        if (is_write) {
> +            val = *((uint8_t *)(buf + i));
> +            trace_vfu_cfg_write((offset + i), val);
> +            pci_default_write_config(PCI_DEVICE(o->pci_dev),
> +                                     (offset + i), val, 1);
> +        } else {
> +            val = pci_default_read_config(PCI_DEVICE(o->pci_dev),
> +                                          (offset + i), 1);
> +            *((uint8_t *)(buf + i)) = (uint8_t)val;
> +            trace_vfu_cfg_read((offset + i), val);
> +        }
> +    }

Is it always OK to split up the access into single bytes like this?

regards
john