On Wed, 23 Aug 2023 14:18:52 +0000
Ankit Agrawal <ankita@xxxxxxxxxx> wrote:
> >> +
> >> + /*
> >> + * Handle read on the BAR2 region. Map to the target device memory
> >> + * physical address and copy to the request read buffer.
> >> + */
> >> + if (copy_to_user(buf, (u8 *)addr + offset, read_count))
> >> + return -EFAULT;
> >
> > Just to verify, does this memory allow access of arbitrary alignment
> > and size?
>
> Please correct me if I'm wrong, but based on following gdb dump data on
> the corresponding MemoryRegion->ops, unaligned access isn't supported, and
> a read of size upto 8 may be done.
>
> (gdb) p/x *(mr->ops)
> $7 = {read = 0xaaab5e0b1c50, write = 0xaaab5e0b1a50, read_with_attrs = 0x0, write_with_attrs = 0x0,
> endianness = 0x2, valid = {min_access_size = 0x1, max_access_size = 0x8, unaligned = 0x0, accepts = 0x0},
> impl = {min_access_size = 0x1, max_access_size = 0x8, unaligned = 0x0}}
This is QEMU policy relative to this region, the kernel interface is
not exclusive to QEMU usage. Thanks,
Alex
