Re: Privilege Levels Below User

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Sujet : Re: Privilege Levels Below User
De : paaronclayton (at) *nospam* gmail.com (Paul A. Clayton)
Groupes : comp.arch
Date : 21. Oct 2024, 01:42:32
Autres entêtes
Organisation : A noiseless patient Spider
Message-ID : <vf8rrr$1jtma$1@dont-email.me>
References : 1 2 3 4 5 6 7 8 9
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THREAD NECROMANCY
On 6/11/24 5:18 PM, MitchAlsup1 wrote:
[snip]
I doubt that RowHammer still works when refreshes are interspersed
between accesses--RowHammer generally works because the events are
not protected by refreshes--the DRC sees the right ROW open and
simple streams at the open bank.
If one refreshes the two adjacent rows to avoid data disruption, those refreshes would be adjacent reads to two other rows so it
seems one would have to be a little cautious about excessively
frequent refreshes.

Also note, there are no instructions in My 66000 that force a cache
to DRAM whereas there are instructions that can force a cache line
into L3.
How does a system suspend to DRAM if it cannot force a writeback
of all dirty lines to memory? I am *guessing* this would not use a
special instruction but rather configuration of power management
that would cause hardware/firmware to clean the cache.
Writing back specific data to persistent memory might also
motivate cache block cleaning operations. Perhaps one could
implement such by copying from a cacheable mapping to a
non-cacheable(I/O?) memory?? (I simply remember that Intel added
instructions to write cache lines to persistent memory.)

L3 is the buffer to DRAM. Nothing gets to DRAM without
going through L3 and nothing comes out of DRM that is not also
buffer by L3. So, if 96 cores simultaneously read a line residing in
DRAM, DRAM is read once and 95 cores are serviced through L3. So,
you can't RowHammer based on reading DRAM, either.
If 128 cores read distinct cache lines from the same page quickly
enough to hammer the adjacent pages but not quickly enough to get
DRAM page open hits, this would seem to require relatively
frequent refreshes of adjacent DRAM rows.
Since the L3/memory controller could see that the DRAM row was
unusually active, it could increase prefetching while the DRAM
row was open and/or queue the accesses longer so that the
hammering frequency was reduced and page open hits would be more
common.
The simple statement that L3 would avoid RowHammer by providing the same cache line to all requesters seemed a bit too simple.
Your design may very well handle all the problematic cases,
perhaps even with minimal performance penalties for inadvertent
hammering and logging/notification for questionable activity just
like for error correction (and has been proposed for detected race
conditions). I just know that these are hard problems.

Date Sujet#  Auteur
7 Jun 24 * Privilege Levels Below User119John Savard
7 Jun 24 +- Re: Privilege Levels Below User1MitchAlsup1
7 Jun 24 +* Re: Privilege Levels Below User9MitchAlsup1
9 Jun 24 i`* Re: Privilege Levels Below User8John Savard
10 Jun 24 i `* Re: Privilege Levels Below User7Lawrence D'Oliveiro
10 Jun 24 i  `* Re: Privilege Levels Below User6John Savard
10 Jun 24 i   +* Re: Privilege Levels Below User4MitchAlsup1
11 Jun 24 i   i+* Re: Privilege Levels Below User2John Savard
11 Jun 24 i   ii`- Re: Privilege Levels Below User1Lawrence D'Oliveiro
11 Jun 24 i   i`- Re: Privilege Levels Below User1Lawrence D'Oliveiro
11 Jun 24 i   `- Re: Privilege Levels Below User1Lawrence D'Oliveiro
8 Jun 24 +* Re: Privilege Levels Below User4Lawrence D'Oliveiro
8 Jun 24 i+- Re: Privilege Levels Below User1John Dallman
8 Jun 24 i`* Re: Not history, Privilege Levels Below User2John Levine
9 Jun 24 i `- Re: Not history, Privilege Levels Below User1Lawrence D'Oliveiro
8 Jun 24 +* Re: Privilege Levels Below User66MitchAlsup1
9 Jun 24 i+* Re: Privilege Levels Below User14Lawrence D'Oliveiro
9 Jun 24 ii+- Re: Privilege Levels Below User1David Schultz
10 Jun 24 ii+* Re: Privilege Levels Below User11Lawrence D'Oliveiro
11 Jun 24 iii+- Re: Privilege Levels Below User1Lawrence D'Oliveiro
11 Jun 24 iii`* Re: time-sharing history, Privilege Levels Below User9John Levine
12 Jun 24 iii `* Re: time-sharing history, Privilege Levels Below User8Lawrence D'Oliveiro
12 Jun 24 iii  `* Re: time-sharing history, Privilege Levels Below User7John Levine
12 Jun 24 iii   +- Re: time-sharing history, Privilege Levels Below User1Lawrence D'Oliveiro
12 Jun 24 iii   `* Re: time-sharing history, Privilege Levels Below User5Lynn Wheeler
13 Jun 24 iii    `* Re: time-sharing history, Privilege Levels Below User4Lawrence D'Oliveiro
13 Jun 24 iii     `* Re: time-sharing history, Privilege Levels Below User3Lynn Wheeler
13 Jun 24 iii      `* Re: time-sharing history, Privilege Levels Below User2Lawrence D'Oliveiro
13 Jun 24 iii       `- Re: time-sharing history, Privilege Levels Below User1Lynn Wheeler
24 Oct 24 ii`- Re: Privilege Levels Below User1MitchAlsup1
9 Jun 24 i+* Re: Privilege Levels Below User2Anton Ertl
10 Jun 24 ii`- Re: Privilege Levels Below User1Lawrence D'Oliveiro
10 Jun 24 i+* Re: Privilege Levels Below User8Anton Ertl
11 Jun 24 ii+* Re: Privilege Levels Below User4Lawrence D'Oliveiro
12 Jun 24 iii+- Re: Privilege Levels Below User1Lawrence D'Oliveiro
12 Jun 24 iii`* Re: Privilege Levels Below User2Thomas Koenig
12 Jun 24 iii `- Re: Privilege Levels Below User1Lawrence D'Oliveiro
11 Jun 24 ii`* Re: Privilege Levels Below User3Lawrence D'Oliveiro
12 Jun 24 ii +- Re: Privilege Levels Below User1George Neuner
12 Jun 24 ii `- Re: Privilege Levels Below User1John Dallman
10 Jun 24 i+* Re: Privilege Levels Below User15Terje Mathisen
10 Jun 24 ii+* Re: Privilege Levels Below User4Michael S
11 Jun 24 iii`* Re: Privilege Levels Below User3Lawrence D'Oliveiro
11 Jun 24 iii `* Re: Privilege Levels Below User2MitchAlsup1
12 Jun 24 iii  `- Re: Privilege Levels Below User1Lawrence D'Oliveiro
11 Jun 24 ii+* Re: Privilege Levels Below User5Lawrence D'Oliveiro
12 Jun 24 iii+- Re: Privilege Levels Below User1Lawrence D'Oliveiro
13 Jun 24 iii`* Re: Privilege Levels Below User3MitchAlsup1
13 Jun 24 iii `* Re: Privilege Levels Below User2Lawrence D'Oliveiro
13 Jun 24 iii  `- Re: Privilege Levels Below User1Michael S
11 Jun 24 ii`* Re: Privilege Levels Below User5Terje Mathisen
11 Jun 24 ii `* Re: Privilege Levels Below User4Michael S
12 Jun 24 ii  +- Re: Privilege Levels Below User1Stefan Monnier
13 Jun 24 ii  `* Re: Privilege Levels Below User2Lawrence D'Oliveiro
14 Jun 24 ii   `- Re: Privilege Levels Below User1Lawrence D'Oliveiro
14 Jun 24 i`* Re: Privilege Levels Below User26Paul A. Clayton
14 Jun 24 i `* Re: Privilege Levels Below User25MitchAlsup1
14 Jun 24 i  +* Re: Privilege Levels Below User4Lawrence D'Oliveiro
14 Jun 24 i  i`* Re: Privilege Levels Below User3John Savard
14 Jun 24 i  i `* Re: Privilege Levels Below User2Lawrence D'Oliveiro
15 Jun 24 i  i  `- Re: Privilege Levels Below User1John Dallman
14 Jun 24 i  `* Re: Privilege Levels Below User20John Savard
15 Jun 24 i   `* Re: Privilege Levels Below User19Thomas Koenig
15 Jun 24 i    `* Re: Privilege Levels Below User18Lawrence D'Oliveiro
15 Jun 24 i     +* Re: Privilege Levels Below User3Anton Ertl
15 Jun 24 i     i+- Re: Privilege Levels Below User1Thomas Koenig
16 Jun 24 i     i`- Re: Privilege Levels Below User1Lawrence D'Oliveiro
15 Jun 24 i     `* Re: Privilege Levels Below User14John Dallman
16 Jun 24 i      +* Re: Privilege Levels Below User12Lawrence D'Oliveiro
16 Jun 24 i      i`* Re: Privilege Levels Below User11Michael S
16 Jun 24 i      i `* Re: Privilege Levels Below User10Lawrence D'Oliveiro
16 Jun 24 i      i  `* Re: Privilege Levels Below User9Michael S
16 Jun 24 i      i   +* Re: Privilege Levels Below User3Thomas Koenig
16 Jun 24 i      i   i`* Re: Privilege Levels Below User2Michael S
16 Jun 24 i      i   i `- Re: Privilege Levels Below User1Terje Mathisen
16 Jun 24 i      i   `* Re: Privilege Levels Below User5Lawrence D'Oliveiro
16 Jun 24 i      i    `* Re: Privilege Levels Below User4Michael S
16 Jun 24 i      i     +- Re: Privilege Levels Below User1Lawrence D'Oliveiro
16 Jun 24 i      i     `* Re: Privilege Levels Below User2Torbjorn Lindgren
17 Jun 24 i      i      `- Re: Privilege Levels Below User1Lawrence D'Oliveiro
16 Jun 24 i      `- Re: Privilege Levels Below User1Robert Swindells
8 Jun 24 +* Re: Privilege Levels Below User7BGB
9 Jun 24 i+* Re: Privilege Levels Below User3MitchAlsup1
9 Jun 24 ii`* Re: Privilege Levels Below User2BGB
10 Jun 24 ii `- Re: Privilege Levels Below User1Lawrence D'Oliveiro
10 Jun 24 i`* Re: Privilege Levels Below User3Terje Mathisen
10 Jun 24 i `* Re: Privilege Levels Below User2Anton Ertl
10 Jun 24 i  `- Re: Privilege Levels Below User1BGB
8 Jun 24 +- Re: Privilege Levels Below User1Chris M. Thomasson
9 Jun 24 +* Re: Privilege Levels Below User2John Savard
11 Jun 24 i`- Re: Privilege Levels Below User1Lawrence D'Oliveiro
9 Jun 24 `* Re: Privilege Levels Below User28John Savard
9 Jun 24  +* Re: Privilege Levels Below User25Anton Ertl
9 Jun 24  i`* Re: Privilege Levels Below User24John Savard
9 Jun 24  i +- Re: Privilege Levels Below User1MitchAlsup1
10 Jun 24  i `* Re: Privilege Levels Below User22Anton Ertl
10 Jun 24  i  +- Re: Privilege Levels Below User1MitchAlsup1
11 Jun 24  i  `* Re: Privilege Levels Below User20John Savard
11 Jun 24  i   +* Re: Privilege Levels Below User14MitchAlsup1
11 Jun 24  i   i+* Re: Privilege Levels Below User3MitchAlsup1
11 Jun 24  i   ii`* Re: Privilege Levels Below User2John Savard
11 Jun 24  i   i`* Re: Privilege Levels Below User10John Savard
11 Jun 24  i   `* Re: Privilege Levels Below User5Niklas Holsti
9 Jun 24  `* Re: Privilege Levels Below User2MitchAlsup1

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