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From: Linus Torvalds <torvalds@linux-foundation.org>
To: Andy Lutomirski <luto@amacapital.net>
Cc: Paolo Bonzini <pbonzini@redhat.com>,
	xen-devel <Xen-devel@lists.xen.org>,
	Arjan van de Ven <arjan@linux.intel.com>,
	Borislav Petkov <bp@alien8.de>, X86 ML <x86@kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	KVM list <kvm@vger.kernel.org>, Andy Lutomirski <luto@kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Peter Zijlstra <peterz@infradead.org>
Subject: Re: [PATCH v4 2/5] x86/msr: Carry on after a non-"safe" MSR access fails without !panic_on_oops
Date: Mon, 14 Mar 2016 11:40:58 -0700	[thread overview]
Message-ID: <CA+55aFy2dNgBJwjd+fRUYQf9OxqGkkcjUEarv+o3QSFTJ6+gJQ@mail.gmail.com> (raw)
In-Reply-To: <CALCETrXAAOcGP7DK+7aKn=2pu=SQ0n_PhG9bV4DcoYcv9epn4A@mail.gmail.com>

On Mon, Mar 14, 2016 at 11:24 AM, Andy Lutomirski <luto@amacapital.net> wrote:
>
> The code in my queue is, literally:
>
> bool ex_handler_rdmsr_unsafe(const struct exception_table_entry *fixup,
>                  struct pt_regs *regs, int trapnr)
> {
>     WARN_ONCE(1, "unchecked MSR access error: RDMSR from 0x%x",
>           (unsigned int)regs->cx);
>
>     /* Pretend that the read succeeded and returned 0. */
>     regs->ip = ex_fixup_addr(fixup);
>     regs->ax = 0;
>     regs->dx = 0;
>     return true;
> }
> EXPORT_SYMBOL(ex_handler_rdmsr_unsafe);

I guess I can live with this, as long as we also extend the
early-fault handling to work with the special exception handlers.

And as long as people start understanding that killing the machine is
a bad bad bad thing. It's a debugging nightmare.

               Linus

  reply	other threads:[~2016-03-14 18:41 UTC|newest]

Thread overview: 46+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-03-12 18:08 [PATCH v4 0/5] [PATCH v3 0/5] Improve non-"safe" MSR access failure handling Andy Lutomirski
2016-03-12 18:08 ` [PATCH v4 1/5] x86/paravirt: Add _safe to the read_msr and write_msr PV hooks Andy Lutomirski
2016-03-14 11:57   ` Borislav Petkov
2016-03-14 17:07     ` Andy Lutomirski
2016-03-14 17:07     ` Andy Lutomirski
2016-03-14 11:57   ` Borislav Petkov
2016-03-12 18:08 ` Andy Lutomirski
2016-03-12 18:08 ` [PATCH v4 2/5] x86/msr: Carry on after a non-"safe" MSR access fails without !panic_on_oops Andy Lutomirski
2016-03-14 12:02   ` Borislav Petkov
2016-03-14 12:02   ` Borislav Petkov
2016-03-14 17:05     ` Andy Lutomirski
2016-03-14 17:11       ` Linus Torvalds
2016-03-14 17:17         ` Andy Lutomirski
2016-03-14 18:04           ` Linus Torvalds
2016-03-14 18:10             ` Andy Lutomirski
2016-03-14 18:15               ` Linus Torvalds
2016-03-14 18:15               ` Linus Torvalds
2016-03-14 18:24                 ` Andy Lutomirski
2016-03-14 18:24                 ` Andy Lutomirski
2016-03-14 18:40                   ` Linus Torvalds [this message]
2016-03-14 18:48                     ` Andy Lutomirski
2016-03-15 10:22                       ` Ingo Molnar
2016-03-15 10:26                         ` Ingo Molnar
2016-03-15 10:26                         ` Ingo Molnar
2016-03-15 10:22                       ` Ingo Molnar
2016-03-14 18:48                     ` Andy Lutomirski
2016-03-14 18:40                   ` Linus Torvalds
2016-03-14 20:18               ` Peter Zijlstra
2016-03-14 20:18               ` Peter Zijlstra
2016-03-14 18:10             ` Andy Lutomirski
2016-03-14 18:10             ` Linus Torvalds
2016-03-14 18:10             ` Linus Torvalds
2016-03-15 10:21             ` Ingo Molnar
2016-03-15 10:21             ` Ingo Molnar
2016-03-14 18:04           ` Linus Torvalds
2016-03-14 17:17         ` Andy Lutomirski
2016-03-14 17:05     ` Andy Lutomirski
2016-03-12 18:08 ` Andy Lutomirski
2016-03-12 18:08 ` [PATCH v4 3/5] x86/paravirt: Add paravirt_{read,write}_msr Andy Lutomirski
2016-03-12 18:08 ` [PATCH v4 3/5] x86/paravirt: Add paravirt_{read, write}_msr Andy Lutomirski
2016-03-12 18:08 ` [PATCH v4 4/5] x86/paravirt: Make "unsafe" MSR accesses unsafe even if PARAVIRT=y Andy Lutomirski
2016-03-12 18:08 ` Andy Lutomirski
2016-03-12 18:08 ` [PATCH v4 5/5] x86/msr: Set the return value to zero when native_rdmsr_safe fails Andy Lutomirski
2016-03-12 18:08   ` Andy Lutomirski
2016-03-14 14:32 ` [Xen-devel] [PATCH v4 0/5] [PATCH v3 0/5] Improve non-"safe" MSR access failure handling Boris Ostrovsky
2016-03-14 14:32 ` Boris Ostrovsky

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