lkml.org 
[lkml]   [2017]   [Nov]   [1]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH 04/23] x86, tlb: make CR4-based TLB flushes more robust
From
Date
On 11/01/2017 02:25 PM, Thomas Gleixner wrote:
>> cr4 = this_cpu_read(cpu_tlbstate.cr4);
>> - /* clear PGE */
>> - native_write_cr4(cr4 & ~X86_CR4_PGE);
>> - /* write old PGE again and flush TLBs */
>> + /*
>> + * This function is only called on systems that support X86_CR4_PGE
>> + * and where always set X86_CR4_PGE. Warn if we are called without
>> + * PGE set.
>> + */
>> + WARN_ON_ONCE(!(cr4 & X86_CR4_PGE));
> Because if CR4_PGE is not set, this warning triggers. So this defeats the
> toggle mode you are implementing.

The warning is there because there is probably plenty of *other* stuff
that breaks if we have X86_FEATURE_PGE=1, but CR4.PGE=0.

The point of this was to make this function do the right thing no matter
what, but warn if it gets called in an unexpected way.

\
 
 \ /
  Last update: 2017-11-01 23:24    [W:0.166 / U:2.372 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site