Re: [PATCH v3 1/4] drivers/iommu: Add page_ext for IOMMU_DEBUG_PAGEALLOC

[Randy Dunlap <rdunlap@infradead.org>]

I missed one other thing:

On 11/24/25 3:13 PM, Randy Dunlap wrote:
> 
> 
> On 11/24/25 12:08 PM, Mostafa Saleh wrote:
>> Add a new config IOMMU_DEBUG_PAGEALLOC, which registers new data to
>> page_ext.
>>
>> This config will be used by the IOMMU API to track pages mapped in
>> the IOMMU to catch drivers trying to free kernel memory that they
>> still map in their domains, causing all types of memory corruption.
>>
>> This behaviour is disabled by default and can be enabled using
>> kernel cmdline iommu.debug_pagealloc.
>>
>> Signed-off-by: Mostafa Saleh <smostafa@google.com>
>> ---
>>  .../admin-guide/kernel-parameters.txt         |  6 ++++
>>  drivers/iommu/Kconfig                         | 19 +++++++++++
>>  drivers/iommu/Makefile                        |  1 +
>>  drivers/iommu/iommu-debug-pagealloc.c         | 32 +++++++++++++++++++
>>  include/linux/iommu-debug-pagealloc.h         | 17 ++++++++++
>>  mm/page_ext.c                                 |  4 +++
>>  6 files changed, 79 insertions(+)
>>  create mode 100644 drivers/iommu/iommu-debug-pagealloc.c
>>  create mode 100644 include/linux/iommu-debug-pagealloc.h
>>
>> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
>> index 6c42061ca20e..dddf435a1c11 100644
>> --- a/Documentation/admin-guide/kernel-parameters.txt
>> +++ b/Documentation/admin-guide/kernel-parameters.txt
>> @@ -2557,6 +2557,12 @@
>>  			1 - Bypass the IOMMU for DMA.
>>  			unset - Use value of CONFIG_IOMMU_DEFAULT_PASSTHROUGH.
>>  
>> +	iommu.debug_pagealloc=

Please note what format the option parameter value takes and possible values,
like iommu.passthrough above here in the kernel-parameters.txt file.

>> +			[KNL,EARLY] When CONFIG_IOMMU_DEBUG_PAGEALLOC is set, this
>> +			parameter enables the feature at boot time. By default, it
>> +			is disabled and the system behave the same way as a kernel
> 
> 			                           behaves
> 
>> +			built without CONFIG_IOMMU_DEBUG_PAGEALLOC.
>> +
>>  	io7=		[HW] IO7 for Marvel-based Alpha systems
>>  			See comment before marvel_specify_io7 in
>>  			arch/alpha/kernel/core_marvel.c.
> 
> 

-- 
~Randy