linux-kernel - Re: [PATCH v2 4/4] iommu/arm: Add BBM Level 2 smmu feature

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20250304161943.GD5011@ziepe.ca>
Date: Tue, 4 Mar 2025 12:19:43 -0400
From: Jason Gunthorpe <jgg@...pe.ca>
To: Ryan Roberts <ryan.roberts@....com>
Cc: Mikołaj Lenczewski <miko.lenczewski@....com>,
	Shameerali Kolothum Thodi <shameerali.kolothum.thodi@...wei.com>,
	"suzuki.poulose@....com" <suzuki.poulose@....com>,
	"yang@...amperecomputing.com" <yang@...amperecomputing.com>,
	"catalin.marinas@....com" <catalin.marinas@....com>,
	"will@...nel.org" <will@...nel.org>,
	"joro@...tes.org" <joro@...tes.org>,
	"jean-philippe@...aro.org" <jean-philippe@...aro.org>,
	"mark.rutland@....com" <mark.rutland@....com>,
	"joey.gouly@....com" <joey.gouly@....com>,
	"oliver.upton@...ux.dev" <oliver.upton@...ux.dev>,
	"james.morse@....com" <james.morse@....com>,
	"broonie@...nel.org" <broonie@...nel.org>,
	"maz@...nel.org" <maz@...nel.org>,
	"david@...hat.com" <david@...hat.com>,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
	"nicolinc@...dia.com" <nicolinc@...dia.com>,
	"mshavit@...gle.com" <mshavit@...gle.com>,
	"jsnitsel@...hat.com" <jsnitsel@...hat.com>,
	"smostafa@...gle.com" <smostafa@...gle.com>,
	"linux-arm-kernel@...ts.infradead.org" <linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"iommu@...ts.linux.dev" <iommu@...ts.linux.dev>
Subject: Re: [PATCH v2 4/4] iommu/arm: Add BBM Level 2 smmu feature

On Tue, Mar 04, 2025 at 04:02:20PM +0000, Ryan Roberts wrote:
> On 04/03/2025 14:26, Jason Gunthorpe wrote:
> > On Mon, Mar 03, 2025 at 07:03:42PM +0000, Mikołaj Lenczewski wrote:
> > 
> >> For example, if we use BBML2 for kernel mappings, does that require us
> >> to repaint all kernel mappings when disabling BBML2 on smmu attach? I
> >> am not sure, but definitely something to be worked out.
> > 
> > No, it would be a per-mm_struct basis only if we did something like
> > that
> > 
> > When the SMMU driver puts a SVA on top of the mm_struct it would
> > disable BBML2 usage only for that mm_struct and it's contained VMAs.
> 
> I guess we would need to figure out some synchonization mechanism if disabling
> BBML2 dynaically per-mm. If there was already a BBML2 operation in flight would
> want to wait for it to end. But that's a problem to solve if/when it's shown to
> be needed, I think.

I have a feeling we can piggyback on the mmu notifiers to achieve this
as all the changes to the PTEs should be bracketed by notifier
callbacks..

Let's hope it isn't needed.

Jasob