linux-kernel - Re: [PATCH 1/2] KVM: arm64: Fix enforcement of upper bound on MDCR

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Message-ID: <ca3054b2-b053-3859-a992-09499809d4d4@huawei.com>
Date: Fri, 4 Jul 2025 14:44:38 +0800
From: Zenghui Yu <yuzenghui@...wei.com>
To: Ben Horgan <ben.horgan@....com>
CC: <catalin.marinas@....com>, <will@...nel.org>, <maz@...nel.org>,
	<oliver.upton@...ux.dev>, <joey.gouly@....com>, <suzuki.poulose@....com>,
	<linux-arm-kernel@...ts.infradead.org>, <kvmarm@...ts.linux.dev>,
	<yury.norov@...il.com>, <linux@...musvillemoes.dk>,
	<linux-kernel@...r.kernel.org>, <james.morse@....com>,
	<stable@...r.kernel.org>
Subject: Re: [PATCH 1/2] KVM: arm64: Fix enforcement of upper bound on
 MDCR_EL2.HPMN

On 2025/7/3 21:57, Ben Horgan wrote:
> Previously, u64_replace_bits() was used to no effect as the return value
> was ignored. Convert to u64p_replace_bits() so the value is updated in
> place.
> 
> Signed-off-by: Ben Horgan <ben.horgan@....com>
> Fixes: efff9dd2fee7 ("KVM: arm64: Handle out-of-bound write to MDCR_EL2.HPMN")
> Cc: Marc Zyngier <maz@...nel.org>
> Cc: stable@...r.kernel.org
> ---
>  arch/arm64/kvm/sys_regs.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
> index 76c2f0da821f..c20bd6f21e60 100644
> --- a/arch/arm64/kvm/sys_regs.c
> +++ b/arch/arm64/kvm/sys_regs.c
> @@ -2624,7 +2624,7 @@ static bool access_mdcr(struct kvm_vcpu *vcpu,
>  	 */
>  	if (hpmn > vcpu->kvm->arch.nr_pmu_counters) {
>  		hpmn = vcpu->kvm->arch.nr_pmu_counters;
> -		u64_replace_bits(val, hpmn, MDCR_EL2_HPMN);
> +		u64p_replace_bits(&val, hpmn, MDCR_EL2_HPMN);
>  	}
>  
>  	__vcpu_assign_sys_reg(vcpu, MDCR_EL2, val);

Reviewed-by: Zenghui Yu <yuzenghui@...wei.com>

Thanks!