linux-kernel - Re: [PATCH v4 2/5] x86/msr: Carry on after a non-"safe" MSR access fails without !panic_on

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Message-ID: <20160315102631.GA27227@gmail.com>
Date:	Tue, 15 Mar 2016 11:26:31 +0100
From:	Ingo Molnar <mingo@...nel.org>
To:	Andy Lutomirski <luto@...capital.net>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Paolo Bonzini <pbonzini@...hat.com>,
	xen-devel <Xen-devel@...ts.xen.org>,
	Arjan van de Ven <arjan@...ux.intel.com>,
	Borislav Petkov <bp@...en8.de>, X86 ML <x86@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	KVM list <kvm@...r.kernel.org>,
	Andy Lutomirski <luto@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH v4 2/5] x86/msr: Carry on after a non-"safe" MSR access
 fails without !panic_on_oops


* Ingo Molnar <mingo@...nel.org> wrote:

> * Andy Lutomirski <luto@...capital.net> wrote:
> 
> > On Mon, Mar 14, 2016 at 11:40 AM, Linus Torvalds
> > <torvalds@...ux-foundation.org> wrote:
> > > On Mon, Mar 14, 2016 at 11:24 AM, Andy Lutomirski <luto@...capital.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.
> > 
> > OK, will do.  I need to rewrork the early IDT code a bit so it
> > generates a real pt_regs layout, but that's arguably a cleanup anyway.
> 
> Ok, with that's I'm pretty happy about it as well.

Note, I think it's pretty clear at this point that this is v4.7 material.

Thanks,

	Ingo