linux-kernel - Re: [PATCH v6 14/14] iommu/arm-smmu-v3: Set MEV bit in nested STE for DoS mitigations

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Message-ID: <Z7dVLNLhP7VfZ-Ph@google.com>
Date: Thu, 20 Feb 2025 16:15:40 +0000
From: Pranjal Shrivastava <praan@...gle.com>
To: Nicolin Chen <nicolinc@...dia.com>
Cc: "Tian, Kevin" <kevin.tian@...el.com>, "jgg@...dia.com" <jgg@...dia.com>,
	"corbet@....net" <corbet@....net>,
	"will@...nel.org" <will@...nel.org>,
	"joro@...tes.org" <joro@...tes.org>,
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	"shuah@...nel.org" <shuah@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"iommu@...ts.linux.dev" <iommu@...ts.linux.dev>,
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	"Liu, Yi L" <yi.l.liu@...el.com>,
	"patches@...ts.linux.dev" <patches@...ts.linux.dev>
Subject: Re: [PATCH v6 14/14] iommu/arm-smmu-v3: Set MEV bit in nested STE
 for DoS mitigations

On Tue, Feb 18, 2025 at 10:53:55AM -0800, Nicolin Chen wrote:
> > > Is MEV available only in nested mode? Otherwise it perhaps makes
> > > sense to turn it on in all configurations in IOMMUFD paths...
> > 
> > I think the arm-smmu-v3's iommufd implementation only supports nested
> > which could be the reason.
> 
> I guess what Kevin says is that non-nested STE should set the MEV
> as well, e.g. BYPASS and ABORT, and perhaps stage-1-only case too
> where the attaching domain = UNMANAGED.
> 

Ohh okay, got it. Thanks!

Praan