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From: Peter Zijlstra <peterz@infradead.org>
To: Nadav Amit <namit@vmware.com>
Cc: Ingo Molnar <mingo@redhat.com>,
LKML <linux-kernel@vger.kernel.org>, X86 ML <x86@kernel.org>,
"H. Peter Anvin" <hpa@zytor.com>,
Thomas Gleixner <tglx@linutronix.de>,
Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
Andy Lutomirski <luto@kernel.org>,
Kees Cook <keescook@chromium.org>,
Dave Hansen <dave.hansen@intel.com>,
Masami Hiramatsu <mhiramat@kernel.org>
Subject: Re: [PATCH v3 6/7] x86/alternatives: use temporary mm for text poking
Date: Tue, 6 Nov 2018 14:11:19 +0100 [thread overview]
Message-ID: <20181106131119.GA9828@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20181106082019.GF22431@hirez.programming.kicks-ass.net>
On Tue, Nov 06, 2018 at 09:20:19AM +0100, Peter Zijlstra wrote:
> By our current way of thinking, kmap_atomic simply is not correct.
Something like the below; which weirdly builds an x86_32 kernel.
Although I imagine a very sad one.
---
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index ba7e3464ee92..e273f3879d04 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -1449,6 +1449,16 @@ config PAGE_OFFSET
config HIGHMEM
def_bool y
depends on X86_32 && (HIGHMEM64G || HIGHMEM4G)
+ depends on !SMP || BROKEN
+ help
+ By current thinking kmap_atomic() is broken, since it relies on per
+ CPU PTEs in the global (kernel) address space and relies on CPU local
+ TLB invalidates to completely invalidate these PTEs. However there is
+ nothing that guarantees other CPUs will not speculatively touch upon
+ 'our' fixmap PTEs and load then into their TLBs, after which our
+ local TLB invalidate will not invalidate them.
+
+ There are AMD chips that will #MC on inconsistent TLB states.
config X86_PAE
bool "PAE (Physical Address Extension) Support"
next prev parent reply other threads:[~2018-11-06 13:11 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-02 23:29 [PATCH v3 0/7] x86/alternatives: text_poke() fixes Nadav Amit
2018-11-02 23:29 ` [PATCH v3 1/7] Fix "x86/alternatives: Lockdep-enforce text_mutex in text_poke*()" Nadav Amit
2018-11-03 10:11 ` Jiri Kosina
2018-11-04 20:58 ` Thomas Gleixner
2018-11-05 18:14 ` Nadav Amit
2018-11-02 23:29 ` [PATCH v3 2/7] x86/jump_label: Use text_poke_early() during early_init Nadav Amit
2018-11-05 12:39 ` Peter Zijlstra
2018-11-05 13:33 ` Peter Zijlstra
2018-11-05 14:09 ` Peter Zijlstra
2018-11-05 17:22 ` Andy Lutomirski
2018-11-05 17:49 ` Nadav Amit
2018-11-05 19:03 ` Andy Lutomirski
2018-11-05 19:25 ` Nadav Amit
2018-11-05 20:05 ` Andy Lutomirski
2018-11-05 20:28 ` Thomas Gleixner
2018-11-05 21:31 ` Nadav Amit
2018-11-07 19:13 ` Nadav Amit
2018-11-08 10:41 ` Peter Zijlstra
2018-11-02 23:29 ` [PATCH v3 3/7] x86/mm: temporary mm struct Nadav Amit
2018-11-02 23:29 ` [PATCH v3 4/7] fork: provide a function for copying init_mm Nadav Amit
2018-11-02 23:29 ` [PATCH v3 5/7] x86/alternatives: initializing temporary mm for patching Nadav Amit
2018-11-02 23:29 ` [PATCH v3 6/7] x86/alternatives: use temporary mm for text poking Nadav Amit
2018-11-05 13:19 ` Peter Zijlstra
2018-11-05 13:30 ` Peter Zijlstra
2018-11-05 18:04 ` Nadav Amit
2018-11-06 8:20 ` Peter Zijlstra
2018-11-06 13:11 ` Peter Zijlstra [this message]
2018-11-06 18:11 ` Nadav Amit
2018-11-06 19:08 ` Peter Zijlstra
2018-11-02 23:29 ` [PATCH v3 7/7] x86/alternatives: remove text_poke() return value Nadav Amit
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