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From: Marc Zyngier <maz@kernel.org>
To: Zhenyu Ye <yezhenyu2@huawei.com>
Cc: <yuzenghui@huawei.com>, <will@kernel.org>,
	<oliver.upton@linux.dev>, <catalin.marinas@arm.com>,
	<joey.gouly@arm.com>, <linux-kernel@vger.kernel.org>,
	<xiexiangyou@huawei.com>, <zhengchuan@huawei.com>,
	<wangzhou1@hisilicon.com>, <linux-arm-kernel@lists.infradead.org>,
	<kvm@vger.kernel.org>, <kvmarm@lists.linux.dev>
Subject: Re: [PATCH v1 3/5] arm64/kvm: using ioctl to enable/disable the HDBSS feature
Date: Tue, 11 Mar 2025 09:59:50 +0000	[thread overview]
Message-ID: <86tt7zopk9.wl-maz@kernel.org> (raw)
In-Reply-To: <20250311040321.1460-4-yezhenyu2@huawei.com>

+1 on everything Oliver said. Additionally:

On Tue, 11 Mar 2025 04:03:19 +0000,
Zhenyu Ye <yezhenyu2@huawei.com> wrote:
> 
> diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
> index 1f55b0c7b11d..9c11e2292b1e 100644
> --- a/arch/arm64/kvm/mmu.c
> +++ b/arch/arm64/kvm/mmu.c
> @@ -1703,6 +1703,9 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
>  	if (writable)
>  		prot |= KVM_PGTABLE_PROT_W;
>  
> +	if (kvm->enable_hdbss && logging_active)
> +		prot |= KVM_PGTABLE_PROT_DBM;
> +

This looks totally wrong. If the page is defined as R/O
(KVM_PGTABLE_PROT_W not being set), setting the DBM flag makes it
writable anyway (the W bit is the Dirty bit). Hello, memory
corruption?

overall, this patch is a total mess, and needs to be split to have the
runtime logic on one side, and the userspace API on the other. Don't
mix the two.

Thanks,

	M.

-- 
Without deviation from the norm, progress is not possible.

  parent reply	other threads:[~2025-03-11  9:59 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2025-03-11  4:03 [PATCH v1 0/5] Support the FEAT_HDBSS introduced in Armv9.5 Zhenyu Ye
2025-03-11  4:03 ` [PATCH v1 1/5] arm64/sysreg: add HDBSS related register information Zhenyu Ye
2025-03-11  9:41   ` Marc Zyngier
2025-03-11  4:03 ` [PATCH v1 2/5] arm64/kvm: support set the DBM attr during memory abort Zhenyu Ye
2025-03-11  9:47   ` Marc Zyngier
2025-03-11  4:03 ` [PATCH v1 3/5] arm64/kvm: using ioctl to enable/disable the HDBSS feature Zhenyu Ye
2025-03-11  8:05   ` Oliver Upton
2025-03-11  9:59   ` Marc Zyngier [this message]
2025-03-11  4:03 ` [PATCH v1 4/5] arm64/kvm: support to handle the HDBSSF event Zhenyu Ye
2025-03-11 10:34   ` Marc Zyngier
2025-03-11  4:03 ` [PATCH v1 5/5] arm64/config: add config to control whether enable HDBSS feature Zhenyu Ye
2025-03-11  9:53   ` Marc Zyngier

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