Re: [PATCH] iommu/vt-d: set INTEL_IOMMU_FLOPPY_WA depend on BLK_DEV_FD

[Baolu Lu <baolu.lu@linux.intel.com>]

On 10/3/25 00:16, Vineeth Pillai (Google) wrote:
> INTEL_IOMMU_FLOPPY_WA workaround was introduced to create direct mappings
> for first 16MB for floppy devices as the floppy drivers were not using
> dma apis. We need not do this direct map if floppy driver is not
> enabled.
> 
> INTEL_IOMMU_FLOPPY_WA is generally not a good idea. Iommu will be
> mapping pages in this address range while kernel would also be
> allocating from this range(mostly on memory stress). A misbehaving
> device using this domain will have access to the pages that the
> kernel might be actively using. We noticed this while running a test
> that was trying to figure out if any pages used by kernel is in iommu
> page tables.
> 
> This patch reduces the scope of the above issue by disabling the
> workaround when floppy driver is not enabled. But we would still need to
> fix the floppy driver to use dma apis so that we need not do direct map
> without reserving the pages. Or the other option is to reserve this
> memory range in firmware so that kernel will not use the pages.
> 
> Fixes: d850c2ee5fe22 ("iommu/vt-d: Expose ISA direct mapping region via iommu_get_resv_regions")
> Fixes: 49a0429e53f2 ("Intel IOMMU: Iommu floppy workaround")
> 
> Signed-off-by: Vineeth Pillai (Google)<vineeth@bitbyteword.org>
> ---
>   drivers/iommu/intel/Kconfig | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)

Queued for v6.19-rc1. Thanks!