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From: Borislav Petkov <bp@alien8.de>
To: Andy Lutomirski <luto@amacapital.net>
Cc: KVM list <kvm@vger.kernel.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	X86 ML <x86@kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	xen-devel <Xen-devel@lists.xen.org>,
	Andy Lutomirski <luto@kernel.org>,
	Paolo Bonzini <pbonzini@redhat.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Arjan van de Ven <arjan@linux.intel.com>
Subject: Re: [PATCH v5 4/9] x86/traps: Enable all exception handler callbacks early
Date: Sat, 2 Apr 2016 22:52:48 +0200	[thread overview]
Message-ID: <20160402205248.GD2538__11457.2582104758$1459630454$gmane$org@pd.tnic> (raw)
In-Reply-To: <CALCETrV7PxgmhU_yXjJSugY88T8Do=vBDuG54fOFSyLp7nGcJA@mail.gmail.com>

On Sat, Apr 02, 2016 at 01:16:07PM -0700, Andy Lutomirski wrote:
> I have no idea why it was explicitly unsupported, but I'm guessing it
> was just to avoid duplicating the code.  Early "ext" uaccess failures
> are certainly not going to work, but I don't think this is a problem
> -- there's no userspace before trap_init runs, so how exactly is an
> "ext" uaccess going to happen in the first place?
> 
> In any event, if it did happen in older kernels, it would have
> immediately panicked due to that code.  At least with my code it just
> might manage to EFAULT correctly.

Yeah, I was wondering what that early thing meant.

Linus or tip guys probably remember what this whole deal with early
uaccess was about. I'll try to do some git archeology tomorrow.

In any event, it would be a good idea IMO, to hold that situation down
in a comment somewhere. Once we've figured it out...

-- 
Regards/Gruss,
    Boris.

ECO tip #101: Trim your mails when you reply.

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  reply	other threads:[~2016-04-02 20:52 UTC|newest]

Thread overview: 101+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-04-02 14:01 [PATCH v5 0/9] Improve non-"safe" MSR access failure handling Andy Lutomirski
2016-04-02 14:01 ` [PATCH v5 1/9] x86/head: Pass a real pt_regs and trapnr to early_fixup_exception Andy Lutomirski
2016-04-02 14:01   ` Andy Lutomirski
2016-04-13 11:43   ` [tip:x86/asm] x86/head: Pass a real pt_regs and trapnr to early_fixup_exception() tip-bot for Andy Lutomirski
2016-04-13 11:43   ` tip-bot for Andy Lutomirski
2016-04-02 14:01 ` [PATCH v5 2/9] x86/head: Move the early NMI fixup into C Andy Lutomirski
2016-04-02 14:01 ` Andy Lutomirski
2016-04-13 11:43   ` [tip:x86/asm] " tip-bot for Andy Lutomirski
2016-04-13 11:43   ` tip-bot for Andy Lutomirski
2016-04-02 14:01 ` [PATCH v5 3/9] x86/head: Move early exception panic code into early_fixup_exception Andy Lutomirski
2016-04-02 14:01   ` Andy Lutomirski
2016-04-02 18:39   ` Borislav Petkov
2016-04-02 18:39   ` Borislav Petkov
2016-04-02 20:13     ` Andy Lutomirski
2016-04-02 20:47       ` Borislav Petkov
2016-04-02 20:47       ` Borislav Petkov
2016-04-02 20:58         ` Andy Lutomirski
2016-04-02 20:58         ` Andy Lutomirski
2016-04-04 11:52           ` Jan Kara
2016-04-04 11:52           ` Jan Kara
2016-04-04 12:46             ` Peter Zijlstra
2016-04-04 12:46             ` Peter Zijlstra
2016-04-04 15:32             ` Andy Lutomirski
2016-04-04 15:36               ` Arjan van de Ven
2016-04-04 15:36               ` Arjan van de Ven
2016-04-04 16:00               ` Peter Zijlstra
2016-04-04 16:00               ` Peter Zijlstra
2016-04-04 19:38                 ` Borislav Petkov
2016-04-04 19:38                 ` Borislav Petkov
2016-04-04 21:31                   ` Andy Lutomirski
2016-04-04 21:40                     ` Borislav Petkov
2016-04-04 21:40                     ` Borislav Petkov
2016-04-04 21:31                   ` Andy Lutomirski
2016-04-04 15:32             ` Andy Lutomirski
2016-04-02 20:13     ` Andy Lutomirski
2016-04-13 11:44   ` [tip:x86/asm] x86/head: Move early exception panic code into early_fixup_exception() tip-bot for Andy Lutomirski
2016-04-13 11:44   ` tip-bot for Andy Lutomirski
2016-04-02 14:01 ` [PATCH v5 4/9] x86/traps: Enable all exception handler callbacks early Andy Lutomirski
2016-04-02 18:52   ` Borislav Petkov
2016-04-02 20:16     ` Andy Lutomirski
2016-04-02 20:52       ` Borislav Petkov [this message]
2016-04-02 20:52       ` Borislav Petkov
2016-04-03  8:07         ` Borislav Petkov
2016-04-03  8:07         ` Borislav Petkov
2016-04-03 13:22           ` Andy Lutomirski
2016-04-03 13:22           ` Andy Lutomirski
2016-04-03 13:51           ` Linus Torvalds
2016-04-03 13:51           ` Linus Torvalds
2016-04-03 13:55             ` Andy Lutomirski
2016-04-03 14:10               ` Borislav Petkov
2016-04-03 14:10               ` Borislav Petkov
2016-04-04 15:47                 ` Andy Lutomirski
2016-04-04 15:47                 ` Andy Lutomirski
2016-04-03 14:17               ` Linus Torvalds
2016-04-03 14:17               ` Linus Torvalds
2016-04-03 13:55             ` Andy Lutomirski
2016-04-02 20:16     ` Andy Lutomirski
2016-04-02 18:52   ` Borislav Petkov
2016-04-13 11:44   ` [tip:x86/asm] " tip-bot for Andy Lutomirski
2016-04-13 11:44   ` tip-bot for Andy Lutomirski
2016-04-02 14:01 ` [PATCH v5 4/9] " Andy Lutomirski
2016-04-02 14:01 ` [PATCH v5 5/9] x86/paravirt: Add _safe to the read_msr and write_msr PV hooks Andy Lutomirski
2016-04-02 14:01   ` Andy Lutomirski
2016-04-03  8:41   ` Borislav Petkov
2016-04-03 13:23     ` Andy Lutomirski
2016-04-03 14:07       ` Borislav Petkov
2016-04-03 14:07       ` Borislav Petkov
2016-04-03 13:23     ` Andy Lutomirski
2016-04-03  8:41   ` Borislav Petkov
2016-04-13 11:44   ` [tip:x86/asm] x86/paravirt: Add _safe to the read_ms()r and write_msr() PV callbacks tip-bot for Andy Lutomirski
2016-04-13 11:44   ` tip-bot for Andy Lutomirski
2016-04-02 14:01 ` [PATCH v5 6/9] x86/msr: Carry on after a non-"safe" MSR access fails Andy Lutomirski
2016-04-02 14:01 ` Andy Lutomirski
2016-04-13 11:45   ` [tip:x86/asm] " tip-bot for Andy Lutomirski
2016-04-13 11:45   ` tip-bot for Andy Lutomirski
2016-04-02 14:01 ` [PATCH v5 7/9] x86/paravirt: Add paravirt_{read, write}_msr Andy Lutomirski
2016-04-02 14:01 ` [PATCH v5 7/9] x86/paravirt: Add paravirt_{read,write}_msr Andy Lutomirski
2016-04-04 16:33   ` [PATCH v5 7/9] x86/paravirt: Add paravirt_{read, write}_msr David Vrabel
2016-04-04 16:33   ` [Xen-devel] " David Vrabel
2016-04-04 16:40     ` Andy Lutomirski
2016-04-04 16:40     ` Andy Lutomirski
2016-04-13 11:45   ` [tip:x86/asm] x86/paravirt: Add paravirt_{read, write}_msr() tip-bot for Andy Lutomirski
2016-04-13 11:45   ` [tip:x86/asm] x86/paravirt: Add paravirt_{read,write}_msr() tip-bot for Andy Lutomirski
2016-04-02 14:01 ` [PATCH v5 8/9] x86/paravirt: Make "unsafe" MSR accesses unsafe even if PARAVIRT=y Andy Lutomirski
2016-04-02 14:01   ` Andy Lutomirski
2016-04-13 11:46   ` [tip:x86/asm] " tip-bot for Andy Lutomirski
2016-04-13 11:46   ` tip-bot for Andy Lutomirski
2016-04-02 14:01 ` [PATCH v5 9/9] x86/msr: Set the return value to zero when native_rdmsr_safe fails Andy Lutomirski
2016-04-13 11:46   ` [tip:x86/asm] x86/msr: Set the return value to zero when native_rdmsr_safe() fails tip-bot for Andy Lutomirski
2016-04-13 11:46   ` tip-bot for Andy Lutomirski
2016-04-02 14:01 ` [PATCH v5 9/9] x86/msr: Set the return value to zero when native_rdmsr_safe fails Andy Lutomirski
2016-04-02 14:24 ` [PATCH v5 0/9] Improve non-"safe" MSR access failure handling Linus Torvalds
2016-04-02 15:13   ` Andy Lutomirski
2016-04-02 15:21     ` Linus Torvalds
2016-04-02 15:21     ` Linus Torvalds
2016-04-02 15:13   ` Andy Lutomirski
2016-04-02 14:24 ` Linus Torvalds
2016-04-04 16:23 ` Borislav Petkov
2016-04-04 16:23 ` Borislav Petkov
2016-04-05 15:38 ` Boris Ostrovsky
2016-04-05 15:38 ` [Xen-devel] " Boris Ostrovsky

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