linux-kernel - Re: [PATCH v3 1/1] iommu/sva: Invalidate KVA range on kernel TLB flush

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Message-ID: <20250828191057.GG7333@nvidia.com>
Date: Thu, 28 Aug 2025 16:10:57 -0300
From: Jason Gunthorpe <jgg@...dia.com>
To: Dave Hansen <dave.hansen@...el.com>
Cc: "Tian, Kevin" <kevin.tian@...el.com>,
	Baolu Lu <baolu.lu@...ux.intel.com>, Joerg Roedel <joro@...tes.org>,
	Will Deacon <will@...nel.org>, Robin Murphy <robin.murphy@....com>,
	Jann Horn <jannh@...gle.com>, Vasant Hegde <vasant.hegde@....com>,
	Alistair Popple <apopple@...dia.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Uladzislau Rezki <urezki@...il.com>,
	Jean-Philippe Brucker <jean-philippe@...aro.org>,
	Andy Lutomirski <luto@...nel.org>, "Lai, Yi1" <yi1.lai@...el.com>,
	"iommu@...ts.linux.dev" <iommu@...ts.linux.dev>,
	"security@...nel.org" <security@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"stable@...r.kernel.org" <stable@...r.kernel.org>,
	"vishal.moola@...il.com" <vishal.moola@...il.com>,
	Matthew Wilcox <willy@...radead.org>
Subject: Re: [PATCH v3 1/1] iommu/sva: Invalidate KVA range on kernel TLB
 flush

On Thu, Aug 28, 2025 at 11:56:00AM -0700, Dave Hansen wrote:
> I got a bit sick of sending constant emails on this one and just decided
> to hack it together myself. Here's roughly what I came up with.
> Completely untested. Changelogs are bare. Barely compiles:
> 
> > https://git.kernel.org/pub/scm/linux/kernel/git/daveh/devel.git/log/?h=kpte
> 
> I also didn't actually hook up the IOMMU flush yet.
> 
> The biggest single chunk of code is defining ptdesc_*_kernel(). The rest
> of it is painfully simple.

Seems not great to be casting ptdesc to folio just to use
folio_set_referenced(), I'm pretty sure that is no the direction
things are going in..

I'd set the flag yourself or perhaps use the memory of __page_mapping
to store a flag (but zero it before freeing).

Looks OK otherwise

Jason