From: Peter Zijlstra <peterz@infradead.org>
To: Dave Hansen <dave.hansen@linux.intel.com>
Cc: linux-kernel@vger.kernel.org, Andy Lutomirski <luto@kernel.org>,
Ingo Molnar <mingo@kernel.org>, Borislav Petkov <bp@alien8.de>,
Brian Gerst <brgerst@gmail.com>,
Denys Vlasenko <dvlasenk@redhat.com>,
"H. Peter Anvin" <hpa@zytor.com>,
Josh Poimboeuf <jpoimboe@redhat.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Rik van Riel <riel@redhat.com>,
daniel.gruss@iaik.tugraz.at, hughd@google.com,
keescook@google.com, linux-mm@kvack.org,
michael.schwarz@iaik.tugraz.at, moritz.lipp@iaik.tugraz.at,
richard.fellner@student.tugraz.at
Subject: Re: [PATCH 4/5] x86/mm/kaiser: Remove superfluous SWITCH_TO_KERNEL
Date: Mon, 27 Nov 2017 23:53:06 +0100 [thread overview]
Message-ID: <20171127225306.6f7iueus7fq2hg7h@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <b96a07a3-9fd5-f4c1-a4d5-433c590d006e@linux.intel.com>
On Mon, Nov 27, 2017 at 02:47:08PM -0800, Dave Hansen wrote:
> On 11/27/2017 02:31 PM, Peter Zijlstra wrote:
> > We never use this code-path with KAISER enabled.
> ...
> > @@ -201,14 +201,6 @@ ENTRY(entry_SYSCALL_64)
> >
> > swapgs
> > movq %rsp, PER_CPU_VAR(rsp_scratch)
> > -
> > - /*
> > - * The kernel CR3 is needed to map the process stack, but we
> > - * need a scratch register to be able to load CR3. %rsp is
> > - * clobberable right now, so use it as a scratch register.
> > - * %rsp will look crazy here for a couple instructions.
> > - */
> > - SWITCH_TO_KERNEL_CR3 scratch_reg=%rsp
> > movq PER_CPU_VAR(cpu_current_top_of_stack), %rsp
>
> What's the mechanism that we use to switch between the two versions of
> the SYSCALL entry? It wasn't obvious from some grepping.
the next patch, the code in tip will in fact never use this code.
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next prev parent reply other threads:[~2017-11-27 22:53 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-11-27 22:31 [PATCH 0/5] KAISER fixlets Peter Zijlstra
2017-11-27 22:31 ` [PATCH 1/5] x86/mm/kaiser: Alternative ESPFIX Peter Zijlstra
2017-11-27 22:39 ` Peter Zijlstra
2017-11-27 22:41 ` Dave Hansen
2017-11-27 22:31 ` [PATCH 2/5] x86/mm/kaiser: Add a banner Peter Zijlstra
2017-11-28 3:36 ` Andy Lutomirski
2017-11-28 5:03 ` Josh Poimboeuf
2017-11-28 5:23 ` Andy Lutomirski
2017-11-28 12:54 ` Borislav Petkov
2017-11-27 22:31 ` [PATCH 3/5] x86/mm/kaiser: Revert ("Map the entry stack variables") Peter Zijlstra
2017-11-27 22:31 ` [PATCH 4/5] x86/mm/kaiser: Remove superfluous SWITCH_TO_KERNEL Peter Zijlstra
2017-11-27 22:47 ` Dave Hansen
2017-11-27 22:53 ` Peter Zijlstra [this message]
2017-11-27 22:31 ` [PATCH 5/5] x86/mm/kaiser: Disable the SYSCALL-64 trampoline along with KAISER Peter Zijlstra
2017-11-27 22:53 ` Dave Hansen
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