The msf2-emac ethernet controller has functions emac_load_desc() and emac_store_desc() which read and write the in-memory descriptor blocks and handle conversion between guest and host endianness.
As currently written, emac_store_desc() does the endianness conversion in-place; this means that it effectively consumes the input EmacDesc struct, because on a big-endian host the fields will be overwritten with the little-endian versions of their values. Unfortunately, in all the callsites the code continues to access fields in the EmacDesc struct after it has called emac_store_desc() -- specifically, it looks at the d.next field. The effect of this is that on a big-endian host networking doesn't work because the address of the next descriptor is corrupted. We could fix this by making the callsite avoid using the struct; but it's more robust to have emac_store_desc() leave its input alone. (emac_load_desc() also does an in-place conversion, but here this is fine, because the function is supposed to be initializing the struct.) Cc: qemu-sta...@nongnu.org Signed-off-by: Peter Maydell <peter.mayd...@linaro.org> --- This is one of a number of issues that prevent 'make check-avocado' working for arm targets on a big-endian host... hw/net/msf2-emac.c | 14 +++++++++----- 1 file changed, 9 insertions(+), 5 deletions(-) diff --git a/hw/net/msf2-emac.c b/hw/net/msf2-emac.c index 7ccd3e51427..34c1f768db0 100644 --- a/hw/net/msf2-emac.c +++ b/hw/net/msf2-emac.c @@ -120,12 +120,16 @@ static void emac_load_desc(MSF2EmacState *s, EmacDesc *d, hwaddr desc) static void emac_store_desc(MSF2EmacState *s, EmacDesc *d, hwaddr desc) { - /* Convert from host endianness into LE. */ - d->pktaddr = cpu_to_le32(d->pktaddr); - d->pktsize = cpu_to_le32(d->pktsize); - d->next = cpu_to_le32(d->next); + EmacDesc outd; + /* + * Convert from host endianness into LE. We use a local struct because + * calling code may still want to look at the fields afterwards. + */ + outd.pktaddr = cpu_to_le32(d->pktaddr); + outd.pktsize = cpu_to_le32(d->pktsize); + outd.next = cpu_to_le32(d->next); - address_space_write(&s->dma_as, desc, MEMTXATTRS_UNSPECIFIED, d, sizeof *d); + address_space_write(&s->dma_as, desc, MEMTXATTRS_UNSPECIFIED, &outd, sizeof outd); } static void msf2_dma_tx(MSF2EmacState *s) -- 2.34.1