lkml.org 
[lkml]   [2020]   [Mar]   [20]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH 21/70] x86/boot/compressed/64: Add function to map a page unencrypted
From
Date
On 3/20/20 1:53 PM, David Rientjes wrote:
>> +
>> + /* Clear encryption flag and write new pte */
>> + pte = pte_clear_flags(*ptep, _PAGE_ENC);
>> + set_pte(ptep, pte);
>> +
>> + /* Flush TLB to map the page unencrypted */
>> + write_cr3(top_level_pgt);
>> +
> Is there a guarantee that this flushes the tlb if cr3 == top_level_pgt
> alrady without an invlpg?

Ahh, good catch.

It *never* flushes global pages. For a generic function like this, that
seems pretty dangerous because the PTEs it goes after could quite easily
be Global. It's also not _obviously_ correct if PCIDs are in play
(which I don't think they are on AMD).

A flush_tlb_global() is probably more appropriate. Better yet, is there
a reason not to use flush_tlb_kernel_range()? I don't think it's
necessary to whack the entire TLB for one PTE set.

\
 
 \ /
  Last update: 2020-03-20 22:02    [W:0.103 / U:8.608 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site