From: Borislav Petkov <bp@alien8.de>
To: Andy Lutomirski <luto@amacapital.net>
Cc: Peter Zijlstra <peterz@infradead.org>,
Valdis Kletnieks <Valdis.Kletnieks@vt.edu>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Paul Mackerras <paulus@samba.org>,
Arnaldo Carvalho de Melo <acme@kernel.org>,
Ingo Molnar <mingo@redhat.com>, Kees Cook <keescook@chromium.org>,
Andrea Arcangeli <aarcange@redhat.com>,
Erik Bosman <ebn310@few.vu.nl>
Subject: Re: [RFC 2/5] x86: Store a per-cpu shadow copy of CR4
Date: Thu, 16 Oct 2014 13:49:17 +0200 [thread overview]
Message-ID: <20141016114917.GD25025@nazgul.tnic> (raw)
In-Reply-To: <808fa43ef6e24d1df47c2666174d997105b9582d.1413323611.git.luto@amacapital.net>
On Tue, Oct 14, 2014 at 03:57:36PM -0700, Andy Lutomirski wrote:
> Context switches and TLB flushes can change individual bits of CR4.
> CR4 reads take several cycles, so store a shadow copy of CR4 in a
> per-cpu variable.
>
> To avoid wasting a cache line, I added the CR4 shadow to
> cpu_tlbstate, which is already touched during context switches.
So does this even show in any workloads as any improvement?
Also, what's the rule with reading the shadow CR4? kvm only? Because
svm_set_cr4() in svm.c reads the host CR4 too.
Should we make all code access the shadow CR4 maybe...
--
Regards/Gruss,
Boris.
--
next prev parent reply other threads:[~2014-10-16 11:49 UTC|newest]
Thread overview: 49+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-10-14 22:57 [RFC 0/5] CR4 handling improvements Andy Lutomirski
2014-10-14 22:57 ` [RFC 1/5] x86: Clean up cr4 manipulation Andy Lutomirski
2014-10-16 8:16 ` Peter Zijlstra
2014-10-16 11:18 ` Borislav Petkov
2014-10-16 11:29 ` Borislav Petkov
2014-10-16 15:32 ` Andy Lutomirski
2014-10-16 15:47 ` Borislav Petkov
2014-10-14 22:57 ` [RFC 2/5] x86: Store a per-cpu shadow copy of CR4 Andy Lutomirski
2014-10-16 8:26 ` Peter Zijlstra
2014-10-16 11:49 ` Borislav Petkov [this message]
2014-10-16 15:30 ` Andy Lutomirski
2014-10-14 22:57 ` [RFC 3/5] x86: Add a comment clarifying LDT context switching Andy Lutomirski
2014-10-16 15:49 ` Borislav Petkov
2014-10-16 16:21 ` Andy Lutomirski
2014-10-21 5:41 ` Borislav Petkov
2014-10-21 5:44 ` Andy Lutomirski
2014-10-21 6:05 ` Borislav Petkov
2014-10-14 22:57 ` [RFC 4/5] perf: Add pmu callbacks to track event mapping and unmapping Andy Lutomirski
2014-10-14 22:57 ` [RFC 5/5] x86,perf: Only allow rdpmc if a perf_event is mapped Andy Lutomirski
2014-10-16 8:42 ` Peter Zijlstra
2014-10-16 15:37 ` Andy Lutomirski
2014-10-16 15:57 ` Borislav Petkov
2014-10-17 0:00 ` Andy Lutomirski
2014-10-19 20:23 ` Andy Lutomirski
2014-10-19 21:33 ` Peter Zijlstra
2014-10-19 22:05 ` Andy Lutomirski
2014-10-19 22:20 ` Peter Zijlstra
2014-10-19 22:57 ` Andy Lutomirski
2014-10-20 8:33 ` Peter Zijlstra
2014-10-20 16:49 ` Andy Lutomirski
2014-10-20 17:39 ` Andy Lutomirski
2014-10-21 8:59 ` Peter Zijlstra
2014-10-19 21:35 ` Peter Zijlstra
2014-10-20 0:08 ` Andy Lutomirski
2014-10-20 8:48 ` Peter Zijlstra
2014-10-20 9:24 ` Martin Schwidefsky
2014-10-20 10:51 ` Hendrik Brueckner
2014-10-21 9:14 ` Peter Zijlstra
2014-10-21 15:52 ` Andy Lutomirski
2014-10-21 4:06 ` [RFC 0/5] CR4 handling improvements Vince Weaver
2014-10-21 4:28 ` Andy Lutomirski
2014-10-21 15:00 ` Vince Weaver
2014-10-21 16:04 ` Peter Zijlstra
2014-10-21 17:05 ` Vince Weaver
2014-10-23 11:42 ` Peter Zijlstra
2014-10-24 12:41 ` Vince Weaver
2014-10-24 22:14 ` Andy Lutomirski
2014-10-15 7:37 [RFC 2/5] x86: Store a per-cpu shadow copy of CR4 Hillf Danton
2014-10-15 14:43 ` Andy Lutomirski
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