[MODERATED] FYI - Reading uncached memory

[MODERATED] FYI - Reading uncached memory

[Jon Masters]

FYI Graz have been able to prove the Intel processors will allow
speculative reads of /explicitly/ UC memory (e.g. marked in MTRR). I
believe they actually use the QPI SAD table to determine what memory is
speculation safe and what memory has side effects (i.e. if it's HA'able
memory then it's deemed ok to rampantly speculate from it).

Just in case anyone thought UC was safe against attacks.

Jon.

-- 
Computer Architect | Sent from my Fedora powered laptop

[MODERATED] Encrypted Message

[Tim Chen]

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From: Tim Chen <tim.c.chen@linux.intel.com>
To: speck for Jon Masters <speck@linutronix.de>
Subject: Re: FYI - Reading uncached memory

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On 06/12/2018 10:29 AM, speck for Jon Masters wrote:
> FYI Graz have been able to prove the Intel processors will allow
> speculative reads of /explicitly/ UC memory (e.g. marked in MTRR). I
> believe they actually use the QPI SAD table to determine what memory is
> speculation safe and what memory has side effects (i.e. if it's HA'able
> memory then it's deemed ok to rampantly speculate from it).
> 
> Just in case anyone thought UC was safe against attacks.
> 
> Jon.
> 

Thanks for forwarding the info.  Yes, the internal Intel team
is aware of this issue.

Tim