Re: [RFC PATCH 12/15] kmap: Add stray write protection for device pages

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On Tue, Jul 14, 2020 at 12:42:11PM -0700, Dave Hansen wrote:
> On 7/14/20 12:29 PM, Peter Zijlstra wrote:
> > On Tue, Jul 14, 2020 at 12:06:16PM -0700, Ira Weiny wrote:
> >> On Tue, Jul 14, 2020 at 10:44:51AM +0200, Peter Zijlstra wrote:
> >>> So, if I followed along correctly, you're proposing to do a WRMSR per
> >>> k{,un}map{_atomic}(), sounds like excellent performance all-round :-(
> >> Only to pages which have this additional protection, ie not DRAM.
> >>
> >> User mappings of this memory is not affected (would be covered by User PKeys if
> >> desired).  User mappings to persistent memory are the primary use case and the
> >> performant path.
> > Because performance to non-volatile memory doesn't matter? I think Dave
> > has a better answer here ...
> 
> So, these WRMSRs are less evil than normal.  They're architecturally
> non-serializing instructions,

Excellent, that should make these a fair bit faster than regular MSRs.

> But, either way, this *will* make accessing PMEM more expensive from the
> kernel.  No escaping that. 

There's no free lunch, it's just that regular MSRs are fairly horrible.



[Index of Archives]     [Kernel Newbies]     [Security]     [Netfilter]     [Bugtraq]     [Linux FS]     [Yosemite Forum]     [MIPS Linux]     [ARM Linux]     [Linux Security]     [Linux RAID]     [Samba]     [Video 4 Linux]     [Device Mapper]     [Linux Resources]

  Powered by Linux