Messages in this thread | | | From | Dan Williams <> | Date | Thu, 3 Feb 2022 21:19:58 -0800 | Subject | Re: [PATCH V8 42/44] dax: Stray access protection for dax_direct_access() |
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On Thu, Jan 27, 2022 at 9:55 AM <ira.weiny@intel.com> wrote: > > From: Ira Weiny <ira.weiny@intel.com> > > dax_direct_access() provides a way to obtain the direct map address of > PMEM memory. Coordinate PKS protection with dax_direct_access() of > protected devmap pages. > > Introduce 3 new dax_operation calls .map_protected .mk_readwrite and > .mk_noaccess. These 3 calls do not have to be implemented by the dax > provider if no protection is implemented. > > Threads of execution can use dax_mk_{readwrite,noaccess}() to relax the > protection of the dax device and allow direct use of the kaddr returned > from dax_direct_access(). The dax_mk_{readwrite,noaccess}() calls only > need to be used to guard actual access to the memory. Other uses of > dax_direct_access() do not need to use these guards. > > For users who require a permanent address to the dax device such as the > DM write cache. dax_map_protected() indicates that the dax device has > additional protections and that user should create it's own permanent > mapping of the memory. Update the DM write cache code to create this > permanent mapping. > > Signed-off-by: Ira Weiny <ira.weiny@intel.com> [..] > diff --git a/include/linux/dax.h b/include/linux/dax.h > index 9fc5f99a0ae2..261af298f89f 100644 > --- a/include/linux/dax.h > +++ b/include/linux/dax.h > @@ -30,6 +30,10 @@ struct dax_operations { > sector_t, sector_t); > /* zero_page_range: required operation. Zero page range */ > int (*zero_page_range)(struct dax_device *, pgoff_t, size_t); > + > + bool (*map_protected)(struct dax_device *dax_dev); > + void (*mk_readwrite)(struct dax_device *dax_dev); > + void (*mk_noaccess)(struct dax_device *dax_dev);
So the dax code just recently jettisoned -the >copy_{to,from}_iter() ops and it would be shame to grow more ops. Given that the implementation is pgmap generic I think all that is needed is way to go from a daxdev to a pgmap and then use the pgmap helpers directly rather than indirecting through the pmem driver just to get the pgmap.
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