[PATCH v13 5/5] arm64: introduce copy_mc_to_kernel() implementation

[Catalin Marinas]

On Mon, Dec 09, 2024 at 10:42:57AM +0800, Tong Tiangen wrote:
> The copy_mc_to_kernel() helper is memory copy implementation that handles
> source exceptions. It can be used in memory copy scenarios that tolerate
> hardware memory errors(e.g: pmem_read/dax_copy_to_iter).
> 
> Currently, only x86 and ppc support this helper, Add this for ARM64 as
> well, if ARCH_HAS_COPY_MC is defined, by implementing copy_mc_to_kernel()
> and memcpy_mc() functions.
> 
> Because there is no caller-saved GPR is available for saving "bytes not
> copied" in memcpy(), the memcpy_mc() is referenced to the implementation
> of copy_from_user(). In addition, the fixup of MOPS insn is not considered
> at present.

Same question as on the previous patch, can we not avoid the memcpy()
duplication if the only difference is entries in the exception table?
IIUC in patch 2 fixup_exception() even ignores the new type. The error
must come on the do_sea() path.

-- 
Catalin