From: Linus Torvalds <torvalds@linux-foundation.org>
To: speck@linutronix.de
Subject: [MODERATED] Re: AMD SSBD extension document
Date: Fri, 18 May 2018 10:04:29 -0700 (PDT) [thread overview]
Message-ID: <alpine.LFD.2.21.999.1805181000250.11543@i7.lan> (raw)
In-Reply-To: <20180518164002.gp72oy264fmtjb6t@ast-mbp.dhcp.thefacebook.com>
On Fri, 18 May 2018, speck for Alexei Starovoitov wrote:
>
> Like, does it disable store-to-load forwarding out of store queue as well?
It really shouldn't, and based on the (limited) performance data I've seen
I don't think it does.
Afaik it only disabled the speculative case of reading the data early when
a previous store hasn't even entered the store buffer yet because the
store address isn't known.
So it's actually the exact reverse of your worry - the bug is that CPU's
will *not* snoop the store buffer (or snoop an even earlier wrong entry in
the store buffer), because they'll try to do the read speculatively early.
Linus
prev parent reply other threads:[~2018-05-18 17:04 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-05-18 15:26 [MODERATED] AMD SSBD extension document Tom Lendacky
2018-05-18 16:40 ` [MODERATED] " Alexei Starovoitov
2018-05-18 17:04 ` Linus Torvalds [this message]
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