Re: [PATCH v8 2/2] lib: checksum: Use aligned accesses for ip_fast_csum and csum_ipv6_magic tests

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On 2/14/24 19:00, John David Anglin wrote:
On 2024-02-14 8:58 p.m., Guenter Roeck wrote:
Specifically: Yes, the carry/borrow bits should be restored. Question is
if the Linux kernel's interrupt handler doesn't restore the carry bits
or if the problem is on the qemu side.
The carry/borrow bits in the PSW should be saved and restored by the save_specials
and rest_specials macros.  They are defined in arch/parisc/include/asm/assembly.h.

However, it appears the tophys macro might clobber the carry bits before they
are saved in intr_save.

Actually, I did some logging and found that the correct carry bits do find their way
into the IPSW register in the Linux kernel. Only when userspace is back after handling
the unaligned LDD, the carry flag is always set to 1, no matter how it was set prior
to the unaligned access.


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