Re: [PATCH v2] sparc64: Add support for Application Data Integrity (ADI)
From: Khalid Aziz
Date: Mon Mar 07 2016 - 10:47:18 EST
On 03/07/2016 08:30 AM, Rob Gardner wrote:
On 03/07/2016 07:07 AM, Khalid Aziz wrote:
On 03/05/2016 09:07 PM, David Miller wrote:
From: Khalid Aziz <khalid.aziz@xxxxxxxxxx>
Date: Wed, 2 Mar 2016 13:39:37 -0700
In this
first implementation I am enabling ADI for hugepages only
since these pages are locked in memory and hence avoid the
issue of saving and restoring tags.
This makes the feature almost entire useless.
Non-hugepages must be in the initial implementation.
Hi David,
Thanks for the feedback. I will get this working for non-hugepages as
well. ADI state of each VMA region is already stored in the VMA itself
in my first implementation, so I do not lose it when the page is
swapped out. The trouble is ADI version tags for each VMA region have
to be stored on the swapped out pages since the ADI version tags are
flushed when TLB entry for a page is flushed.
Khalid,
Are you sure about that last statement? My understanding is that the
tags are stored in physical memory, and remain there until explicitly
changed or removed, and so flushing a TLB entry has no effect on the ADI
tags. If it worked the way you think, then somebody would have to
potentially reload a long list of ADI tags on every TLB miss.
Rob
Hi Rob,
I am fairly sure that is the case. This is what I found from the
processor guys and others working on ADI. I tested it out by setting up
ADI on normal malloc'd pages that got swapped out and I got MCD
exceptions when those pages were swapped back in on access.
I mis-spoke when I said "....ADI version tags are flushed when TLB entry
for a page is flushed". I meant ADI version tags are flushed when
mapping for a virtual address is removed from TSB, not when TLB entry is
flushed. Yes, ADI tags are stored in physical memory and removed when
mapping is removed.
Thanks,
Khalid