linux-kernel - Re: [PATCH] Add a text

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Message-ID: <20131129203550.GA14723@redhat.com>
Date:	Fri, 29 Nov 2013 21:35:50 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Andi Kleen <andi@...stfloor.org>, linux-kernel@...r.kernel.org,
	torvalds@...ux-foundation.org, x86@...nel.org,
	Andi Kleen <ak@...ux.intel.com>,
	Ingo Molnar <mingo@...nel.org>, Borislav Petkov <bp@...en8.de>
Subject: Re: [PATCH] Add a text_poke syscall v2

On 11/29, H. Peter Anvin wrote:
>
> On 11/29/2013 12:05 PM, Oleg Nesterov wrote:
> >
> > Can't we invalidate pte (so that any user will stuck in page fault),
> > update the page(s), restore the pte and drop the locks?
> >
>
> That would require a global TLB shootdown

Well, it is not really global, it is for mm_cpumask() and for good
reason?

And is it really worse than on_each_cpu(do_sync_core) and the usage
of text_mutex?

> (and wouldn't help
> shared-memory code segments, if we care about that at all.)

Well, I think this should only support the private mappings.

> It also
> means much bigger code ranges would be affected.

Yes, this is true.

Oleg.

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