On Mon, Dec 11, 2023 at 10:31 PM Cédric Le Goater <c...@redhat.com> wrote: > FWIW, there has been a previous proposal for unaligned accesses support [1]. > > Thanks, > > C. > > [1] https://lore.kernel.org/qemu-devel/20170630030058.28943-1-and...@aj.id.au/ >
Thanks for your information. This patch is an RFC, and unfortunately it doesn't seem to have been merged. This feature is useful for devices that allow unaligned access. Regards, Tomoyuki HIROSE On Mon, Dec 11, 2023 at 10:31 PM Cédric Le Goater <c...@redhat.com> wrote: > > Hello, > > On 12/11/23 08:12, Tomoyuki HIROSE wrote: > > The previous code ignored 'impl.unaligned' and handled unaligned accesses > > as is. But this implementation cannot emulate specific registers of some > > devices that allow unaligned access such as xHCI Host Controller Capability > > Registers. > > This commit checks 'impl.unaligned' and if it is false, QEMU emulates > > unaligned access with multiple aligned access. > > > > Signed-off-by: Tomoyuki HIROSE <tomoyuki.hir...@igel.co.jp> > > FWIW, there has been a previous proposal for unaligned accesses support [1]. > > Thanks, > > C. > > [1] https://lore.kernel.org/qemu-devel/20170630030058.28943-1-and...@aj.id.au/ > > > > --- > > system/memory.c | 22 ++++++++++++++++------ > > 1 file changed, 16 insertions(+), 6 deletions(-) > > > > diff --git a/system/memory.c b/system/memory.c > > index 798b6c0a17..b0caa90fef 100644 > > --- a/system/memory.c > > +++ b/system/memory.c > > @@ -539,6 +539,9 @@ static MemTxResult access_with_adjusted_size(hwaddr > > addr, > > unsigned i; > > MemTxResult r = MEMTX_OK; > > bool reentrancy_guard_applied = false; > > + hwaddr aligned_addr; > > + unsigned corrected_size = size; > > + signed align_diff = 0; > > > > if (!access_size_min) { > > access_size_min = 1; > > @@ -560,18 +563,25 @@ static MemTxResult access_with_adjusted_size(hwaddr > > addr, > > reentrancy_guard_applied = true; > > } > > > > - /* FIXME: support unaligned access? */ > > access_size = MAX(MIN(size, access_size_max), access_size_min); > > access_mask = MAKE_64BIT_MASK(0, access_size * 8); > > + if (!mr->ops->impl.unaligned) { > > + aligned_addr = addr & ~(access_size - 1); > > + align_diff = addr - aligned_addr; > > + corrected_size = size < access_size ? access_size : > > + size + (align_diff > 0 ? access_size : 0); > > + addr = aligned_addr; > > + } > > if (memory_region_big_endian(mr)) { > > - for (i = 0; i < size; i += access_size) { > > + for (i = 0; i < corrected_size; i += access_size) { > > r |= access_fn(mr, addr + i, value, access_size, > > - (size - access_size - i) * 8, access_mask, attrs); > > + (size - access_size - i + align_diff) * 8, > > + access_mask, attrs); > > } > > } else { > > - for (i = 0; i < size; i += access_size) { > > - r |= access_fn(mr, addr + i, value, access_size, i * 8, > > - access_mask, attrs); > > + for (i = 0; i < corrected_size; i += access_size) { > > + r |= access_fn(mr, addr + i, value, access_size, > > + ((signed)i - align_diff) * 8, access_mask, attrs); > > } > > } > > if (mr->dev && reentrancy_guard_applied) { >
