linux-kernel - Re: [PATCH v8 2/2] lib: checksum: Use aligned accesses for ip_fast_csum and csum_ipv6

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Message-ID: <1d5e059e-5b31-415d-ae41-593415812e94@bell.net>
Date: Wed, 14 Feb 2024 22:00:37 -0500
From: John David Anglin <dave.anglin@...l.net>
To: Guenter Roeck <linux@...ck-us.net>, Charlie Jenkins <charlie@...osinc.com>
Cc: David Laight <David.Laight@...lab.com>,
 Palmer Dabbelt <palmer@...belt.com>,
 Andrew Morton <akpm@...ux-foundation.org>, Helge Deller <deller@....de>,
 "James E.J. Bottomley" <James.Bottomley@...senpartnership.com>,
 Parisc List <linux-parisc@...r.kernel.org>, Al Viro
 <viro@...iv.linux.org.uk>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v8 2/2] lib: checksum: Use aligned accesses for
 ip_fast_csum and csum_ipv6_magic tests

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.

Dave

-- 
John David Anglin  dave.anglin@...l.net