From: Ingo Molnar <mingo@kernel.org>
To: Denys Vlasenko <vda.linux@googlemail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>,
Brian Gerst <brgerst@gmail.com>,
Andy Lutomirski <luto@amacapital.net>,
Borislav Petkov <bp@alien8.de>,
the arch/x86 maintainers <x86@kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: [PATCH] x86/asm/entry/64: better check for canonical address
Date: Tue, 31 Mar 2015 18:43:37 +0200 [thread overview]
Message-ID: <20150331164337.GA8462@gmail.com> (raw)
In-Reply-To: <CAK1hOcOOQAq1sWdnK+nTZBightFaJWiTeQCmCPzhG0-y-UYvOw@mail.gmail.com>
* Denys Vlasenko <vda.linux@googlemail.com> wrote:
> > I guess they could optimize it by adding a single "I am a modern
> > OS executing regular userspace" flag to the descriptor [or
> > expressing the same as a separate instruction], to avoid all that
> > legacy crap that won't trigger on like 99.999999% of systems ...
>
> Yes, that would be a useful addition. Interrupt servicing on x86
> takes a non-negligible hit because of IRET slowness.
But ... to react to your other patch: detecting the common easy case
and doing a POPF+RET ourselves ought to be pretty good as well?
But only if ptregs->rip != the magic RET itself, to avoid recursion.
Even with all those extra checks it should still be much faster.
Thanks,
Ingo
next prev parent reply other threads:[~2015-03-31 16:43 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-03-26 12:42 [PATCH] x86/asm/entry/64: better check for canonical address Denys Vlasenko
2015-03-26 18:45 ` Andy Lutomirski
2015-03-27 8:57 ` Borislav Petkov
2015-03-30 14:27 ` Denys Vlasenko
2015-03-30 14:30 ` Andy Lutomirski
2015-03-30 14:45 ` Andy Lutomirski
2015-03-27 8:11 ` Ingo Molnar
2015-03-27 10:45 ` Denys Vlasenko
2015-03-27 11:17 ` Ingo Molnar
2015-03-27 11:28 ` Brian Gerst
2015-03-27 11:34 ` Ingo Molnar
2015-03-27 12:14 ` Denys Vlasenko
2015-03-27 12:16 ` Ingo Molnar
2015-03-27 12:31 ` Denys Vlasenko
2015-03-28 9:11 ` Ingo Molnar
2015-03-29 19:36 ` Denys Vlasenko
2015-03-29 21:12 ` Andy Lutomirski
2015-03-29 21:46 ` Denys Vlasenko
2015-03-31 16:43 ` Ingo Molnar [this message]
2015-03-31 17:08 ` Andy Lutomirski
2015-03-31 17:31 ` Denys Vlasenko
2015-03-27 11:27 ` Brian Gerst
2015-03-27 11:31 ` Ingo Molnar
2015-03-27 21:37 ` Andy Lutomirski
2015-04-02 17:37 ` Denys Vlasenko
2015-04-02 18:10 ` Ingo Molnar
-- strict thread matches above, loose matches on Subject: below --
2015-04-21 16:27 Denys Vlasenko
2015-04-21 18:08 ` Andy Lutomirski
2015-04-23 15:10 ` Borislav Petkov
2015-04-23 15:41 ` Andy Lutomirski
2015-04-23 15:49 ` Borislav Petkov
2015-04-23 15:52 ` Andy Lutomirski
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