Re: [PATCH] KVM: arm64: fix u64_replace_bits() usage

[Marc Zyngier <maz@kernel.org>]

On Fri, 11 Jul 2025 09:44:23 +0100,
"Arnd Bergmann" <arnd@arndb.de> wrote:
> 
> On Fri, Jul 11, 2025, at 10:36, Marc Zyngier wrote:
> > On Fri, 11 Jul 2025 08:27:47 +0100, Arnd Bergmann <arnd@kernel.org> wrote:
> >>  	if (hpmn > vcpu->kvm->arch.nr_pmu_counters) {
> >>  		hpmn = vcpu->kvm->arch.nr_pmu_counters;
> >> -		u64_replace_bits(val, hpmn, MDCR_EL2_HPMN);
> >> +		val = u64_replace_bits(val, hpmn, MDCR_EL2_HPMN);
> >>  	}
> >>  
> >>  	__vcpu_assign_sys_reg(vcpu, MDCR_EL2, val);
> >
> > This is only in -next, right? Because I have a fix for this already
> > queued for 6.16, as per [1].
> 
> Yes, as far as I can tell, the warning only showed up in linux-next
> after f66f9c3d09c1 ("bitfield: Ensure the return values of helper
> functions are checked").
> 
> As far as I can tell, Ben added the check in linux/bitfield.h
> when he sent you his version of the fix, they just ended up
> in linux-next in the wrong order, so I ended up recreating his
> original fix slightly differently.

I don't think Ben's fix is in -next, as I queued it in the kvmarm
fixes branch, which isn't pulled by -next.

Hopefully Paolo will send this to Linus shortly (pull request
here[1]), and -next will be clean again.

Thanks,

	M.

[1] https://lore.kernel.org/r/20250711084835.2411230-1-maz@kernel.org

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