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From: Peter Zijlstra <peterz@infradead.org>
To: Ingo Molnar <mingo@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>,
	LKML <linux-kernel@vger.kernel.org>,
	x86@kernel.org, Juergen Gross <jgross@suse.com>,
	Andi Kleen <ak@linux.intel.com>
Subject: Re: x86/paravirt: Detect over-sized patching bugs in paravirt_patch_call()
Date: Thu, 25 Apr 2019 12:22:10 +0200	[thread overview]
Message-ID: <20190425102210.GM4038@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20190425095039.GC115378@gmail.com>

On Thu, Apr 25, 2019 at 11:50:39AM +0200, Ingo Molnar wrote:
> 
> * Peter Zijlstra <peterz@infradead.org> wrote:
> 
> > On Thu, Apr 25, 2019 at 11:17:17AM +0200, Ingo Molnar wrote:
> > > It basically means that we silently won't do any patching and the kernel 
> > > will crash later on in mysterious ways, because paravirt patching is 
> > > usually relied on.
> > 
> > That's OK. The compiler emits an indirect CALL/JMP to the pv_ops
> > structure contents. That _should_ stay valid and function correctly at
> > all times.
> 
> It might result in a correctly executing kernel in terms of code 
> generation, but it doesn't result in a viable kernel: some of the places 
> rely on the patching going through and don't know what to do when it 
> doesn't and misbehave or crash in interesting ways.
> 
> Guess how I know this. ;-)

What sites would that be? It really should work AFAIK.

  reply	other threads:[~2019-04-25 10:22 UTC|newest]

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-04-24 13:41 [patch 0/3] x86/paravirt: Rework paravirt patching Thomas Gleixner
2019-04-24 13:41 ` [patch 1/3] x86/paravirt: Remove bogus extern declarations Thomas Gleixner
2019-04-25  7:31   ` [tip:x86/paravirt] " tip-bot for Thomas Gleixner
2019-05-24  7:58   ` tip-bot for Thomas Gleixner
2019-04-24 13:41 ` [patch 2/3] x86/paravirt: Unify 32/64 bit patch code Thomas Gleixner
2019-04-25  7:32   ` [tip:x86/paravirt] " tip-bot for Thomas Gleixner
2019-05-24  8:00   ` [tip:x86/paravirt] x86/paravirt: Unify the 32/64 bit paravirt patching code tip-bot for Thomas Gleixner
2019-04-24 13:41 ` [patch 3/3] x86/paravirt: Replace paravirt patch asm magic Thomas Gleixner
2019-04-25  6:52   ` Ingo Molnar
2019-04-25  7:22     ` Thomas Gleixner
2019-04-25  7:46       ` Juergen Gross
2019-04-25  8:10       ` [PATCH] x86/paravirt: Match paravirt patchlet field definition ordering to initialization ordering Ingo Molnar
2019-04-25  9:17         ` [PATCH] x86/paravirt: Detect oversized patching bugs as they happen and BUG_ON() to avoid later crashes Ingo Molnar
2019-04-25  9:21           ` Peter Zijlstra
2019-04-25  9:50             ` x86/paravirt: Detect over-sized patching bugs in paravirt_patch_call() Ingo Molnar
2019-04-25 10:22               ` Peter Zijlstra [this message]
2019-04-25 10:57                 ` Ingo Molnar
2019-04-25 11:30                   ` Juergen Gross
2019-04-25 12:30                     ` Juergen Gross
2019-04-25 11:40                   ` Peter Zijlstra
2019-04-25 12:30                     ` Peter Zijlstra
2019-05-24  7:59               ` [tip:x86/paravirt] " tip-bot for Ingo Molnar
2019-05-24  7:58           ` [tip:x86/paravirt] x86/paravirt: Detect over-sized patching bugs in paravirt_patch_insns() tip-bot for Ingo Molnar
2019-05-24  8:01         ` [tip:x86/paravirt] x86/paravirt: Match paravirt patchlet field definition ordering to initialization ordering tip-bot for Ingo Molnar
2019-04-25  8:08     ` [patch 3/3] x86/paravirt: Replace paravirt patch asm magic Peter Zijlstra
2019-04-25  8:19       ` Peter Zijlstra
2019-04-25  9:20       ` Ingo Molnar
2019-05-24  8:00   ` [tip:x86/paravirt] x86/paravirt: Replace the " tip-bot for Thomas Gleixner

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