Re: [RFC PATCH 1/4] drivers/iommu: Add page_ext for IOMMU_DEBUG_PAGEALLOC

[Mostafa Saleh <smostafa@google.com>]

On Mon, Oct 27, 2025 at 12:42:09PM +0100, Jörg Rödel wrote:
> On Fri, Oct 03, 2025 at 05:32:26PM +0000, Mostafa Saleh wrote:
> > +config IOMMU_DEBUG_PAGEALLOC
> > +	bool "Debug page memory allocations against IOMMU"
> > +	depends on DEBUG_PAGEALLOC && IOMMU_API && PAGE_EXTENSION
> > +	help
> > +		This config checks when a page is freed by the kernel
> > +		it's not mapped in any IOMMU domain. It can help with
> > +		debugging use-after-free from driver doing DMA.
> > +		This santaizer can have false-negative cases where some
> > +		problems won't be detected.
> > +		Expect overhead when enabling this + enabling the kernel
> > +		command line iommu.debug_pagealloc.
> > +
> > +		If unsure, say N here.
> 
> Expected indentation here is <tab><space><space> and not <tab><tab>.

My bad, I will fix it in v2.

> 
> > --- /dev/null
> > +++ b/drivers/iommu/iommu-debug.c
> 
> Is there a plan for this file to contain more than page-alloc debugging? If
> not, it should get a more specific name, like iommu-debug-pagealloc.c or
> similar.


I have no solid plans for other features, but I was hoping to build on top
of that in the future, but for now we can make it “iommu-debug-pagealloc.c”

Thanks,
Mostafa

>