Re: [PATCH 1/3] include/hw/pci: Attach BDF to Memory Attributes

["Michael S. Tsirkin" <mst@redhat.com>]

On Sun, Mar 02, 2025 at 05:12:07PM +0800, Jason Chien wrote:
> This commit adds the BDF to the memory attributes for DMA operations.
> 
> Signed-off-by: Jason Chien <jason.chien@sifive.com>
> ---
>  include/hw/pci/pci_device.h | 10 ++++++++--
>  1 file changed, 8 insertions(+), 2 deletions(-)
> 
> diff --git a/include/hw/pci/pci_device.h b/include/hw/pci/pci_device.h
> index add208edfa..968f1ba3e9 100644
> --- a/include/hw/pci/pci_device.h
> +++ b/include/hw/pci/pci_device.h
> @@ -244,6 +244,8 @@ static inline MemTxResult pci_dma_rw(PCIDevice *dev, dma_addr_t addr,
>                                       void *buf, dma_addr_t len,
>                                       DMADirection dir, MemTxAttrs attrs)
>  {
> +    attrs.unspecified = 0;
> +    attrs.requester_id = pci_requester_id(dev);
>      return dma_memory_rw(pci_get_address_space(dev), addr, buf, len,
>                           dir, attrs);
>  }
> @@ -292,6 +294,8 @@ static inline MemTxResult pci_dma_write(PCIDevice *dev, dma_addr_t addr,
>                                                 uint##_bits##_t *val, \
>                                                 MemTxAttrs attrs) \
>      { \
> +        attrs.unspecified = 0; \
> +        attrs.requester_id = pci_requester_id(dev); \
>          return ld##_l##_dma(pci_get_address_space(dev), addr, val, attrs); \
>      } \
>      static inline MemTxResult st##_s##_pci_dma(PCIDevice *dev, \
> @@ -299,6 +303,8 @@ static inline MemTxResult pci_dma_write(PCIDevice *dev, dma_addr_t addr,
>                                                 uint##_bits##_t val, \
>                                                 MemTxAttrs attrs) \
>      { \
> +        attrs.unspecified = 0; \
> +        attrs.requester_id = pci_requester_id(dev); \
>          return st##_s##_dma(pci_get_address_space(dev), addr, val, attrs); \
>      }
>  
> @@ -327,8 +333,8 @@ PCI_DMA_DEFINE_LDST(q_be, q_be, 64);
>  static inline void *pci_dma_map(PCIDevice *dev, dma_addr_t addr,
>                                  dma_addr_t *plen, DMADirection dir)
>  {
> -    return dma_memory_map(pci_get_address_space(dev), addr, plen, dir,
> -                          MEMTXATTRS_UNSPECIFIED);
> +    MemTxAttrs attrs = {.requester_id = pci_requester_id(dev)};
> +    return dma_memory_map(pci_get_address_space(dev), addr, plen, dir, attrs);
>  }


Map is the only issue  - bdf can technically change between map and
unmap.
The use in hw/net/net_tx_pkt.c is fine as it's under BQL.
I don't know about the use in megasas though.
I think it is probably fine as it seems to deal with commands
and I think any driver would flush these if changing BDF.
Cc megasas maintainers just to make sure though.

Also, adding a code comment here can't hurt.


>  static inline void pci_dma_unmap(PCIDevice *dev, void *buffer, dma_addr_t len,
> -- 
> 2.43.2