[PATCH v9 10/24] mm/hmm: let users to tag specific PFN with DMA mapped bit

[Leon Romanovsky]

On Wed, Apr 23, 2025 at 08:33:35PM -0300, Jason Gunthorpe wrote:
> On Wed, Apr 23, 2025 at 09:37:24PM +0300, Mika Penttilä wrote:
> > 
> > On 4/23/25 21:17, Jason Gunthorpe wrote:
> > > On Wed, Apr 23, 2025 at 08:54:05PM +0300, Mika Penttilä wrote:
> > >>> @@ -36,6 +38,13 @@ enum hmm_pfn_flags {
> > >>>  	HMM_PFN_VALID = 1UL << (BITS_PER_LONG - 1),
> > >>>  	HMM_PFN_WRITE = 1UL << (BITS_PER_LONG - 2),
> > >>>  	HMM_PFN_ERROR = 1UL << (BITS_PER_LONG - 3),
> > >>> +
> > >>> +	/*
> > >>> +	 * Sticky flags, carried from input to output,
> > >>> +	 * don't forget to update HMM_PFN_INOUT_FLAGS
> > >>> +	 */
> > >>> +	HMM_PFN_DMA_MAPPED = 1UL << (BITS_PER_LONG - 7),
> > >>> +
> > >> How is this playing together with the mapped order usage?
> > > Order shift starts at bit 8, DMA_MAPPED is at bit 7
> > 
> > hmm bits are the high bits, and order is 5 bits starting from
> > (BITS_PER_LONG - 8)
> 
> I see, so yes order occupies 5 bits [-4,-5,-6,-7,-8] and the
> DMA_MAPPED overlaps, it should be 9 not 7 because of the backwardness.

Thanks for the fix.