Re: [PATCH RESEND] mshv: Use try_cmpxchg() instead of cmpxchg()

[Wei Liu]

On Wed, Feb 18, 2026 at 12:00:18PM +0100, Uros Bizjak wrote:
> Use !try_cmpxchg() instead of cmpxchg (*ptr, old, new) != old.
> x86 CMPXCHG instruction returns success in ZF flag, so this
> change saves a compare after CMPXCHG.
> 
> The generated assembly code improves from e.g.:
> 
>      415:	48 8b 44 24 30       	mov    0x30(%rsp),%rax
>      41a:	48 8b 54 24 38       	mov    0x38(%rsp),%rdx
>      41f:	f0 49 0f b1 91 a8 02 	lock cmpxchg %rdx,0x2a8(%r9)
>      426:	00 00
>      428:	48 3b 44 24 30       	cmp    0x30(%rsp),%rax
>      42d:	0f 84 09 ff ff ff    	je     33c <...>
> 
> to:
> 
>      415:	48 8b 44 24 30       	mov    0x30(%rsp),%rax
>      41a:	48 8b 54 24 38       	mov    0x38(%rsp),%rdx
>      41f:	f0 49 0f b1 91 a8 02 	lock cmpxchg %rdx,0x2a8(%r9)
>      426:	00 00
>      428:	0f 84 0e ff ff ff    	je     33c <...>
> 
> No functional change intended.
> 
> Signed-off-by: Uros Bizjak <ubizjak@xxxxxxxxx>
> Cc: "K. Y. Srinivasan" <kys@xxxxxxxxxxxxx>
> Cc: Haiyang Zhang <haiyangz@xxxxxxxxxxxxx>
> Cc: Wei Liu <wei.liu@xxxxxxxxxx>
> Cc: Dexuan Cui <decui@xxxxxxxxxxxxx>
> Cc: Long Li <longli@xxxxxxxxxxxxx>

Applied. Thanks.