Re: [PATCH] fix host-endianness bug

[Peter Maydell]

On Wed, 24 Apr 2024 at 19:13, Alexandra Diupina <adiupina@astralinux.ru> wrote:
>
> Add a function xlnx_dpdma_read_descriptor() that
> combines reading the descriptor from desc_addr
> by calling dma_memory_read() and swapping desc
> fields from guest memory order to host memory order.
>
> Found by Linux Verification Center (linuxtesting.org) with SVACE.
>
> Fixes: d3c6369a96 ("introduce xlnx-dpdma")
> Signed-off-by: Alexandra Diupina <adiupina@astralinux.ru>
> ---
>  hw/dma/xlnx_dpdma.c | 38 +++++++++++++++++++++++++++++++++-----
>  1 file changed, 33 insertions(+), 5 deletions(-)
>
> diff --git a/hw/dma/xlnx_dpdma.c b/hw/dma/xlnx_dpdma.c
> index 1f5cd64ed1..5fd4e31699 100644
> --- a/hw/dma/xlnx_dpdma.c
> +++ b/hw/dma/xlnx_dpdma.c
> @@ -614,6 +614,38 @@ static void xlnx_dpdma_register_types(void)
>      type_register_static(&xlnx_dpdma_info);
>  }
>
> +static MemTxResult xlnx_dpdma_read_descriptor(XlnxDPDMAState *s, uint8_t 
> channel,
> +                                        uint64_t desc_addr, DPDMADescriptor 
> *desc)
> +{
> +    if (dma_memory_read(&address_space_memory, desc_addr, &desc,
> +                            sizeof(DPDMADescriptor), 
> MEMTXATTRS_UNSPECIFIED)) {
> +        s->registers[DPDMA_EISR] |= ((1 << 1) << channel);
> +        xlnx_dpdma_update_irq(s);
> +        s->operation_finished[channel] = true;

I think these three lines in the if() here should remain at the callsite --
although we only have one place that reads a descriptor at the
moment, different callers might in theory handle the descriptor-read
failure differently.

> +        return MEMTX_ERROR;

Otherwise this looks good; thanks.

-- PMM