linux-kernel - RE: [PATCH 09/13] unicore: mmu

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <010601cbdd7b$3e388b00$baa9a100$@mprc.pku.edu.cn>
Date:	Tue, 8 Mar 2011 18:25:57 +0800
From:	"Guan Xuetao" <gxt@...c.pku.edu.cn>
To:	"'Peter Zijlstra'" <a.p.zijlstra@...llo.nl>
Cc:	<linux-kernel@...r.kernel.org>, <linux-arch@...r.kernel.org>,
	<linux-mm@...ck.org>,
	"'Benjamin Herrenschmidt'" <benh@...nel.crashing.org>,
	"'David Miller'" <davem@...emloft.net>,
	"'Hugh Dickins'" <hugh.dickins@...cali.co.uk>,
	"'Mel Gorman'" <mel@....ul.ie>,
	"'Nick Piggin'" <npiggin@...nel.dk>,
	"'Paul McKenney'" <paulmck@...ux.vnet.ibm.com>,
	"'Yanmin Zhang'" <yanmin_zhang@...ux.intel.com>,
	"'Andrea Arcangeli'" <aarcange@...hat.com>,
	"'Avi Kivity'" <avi@...hat.com>,
	"'Thomas Gleixner'" <tglx@...utronix.de>,
	"'Rik van Riel'" <riel@...hat.com>,
	"'Ingo Molnar'" <mingo@...e.hu>, <akpm@...ux-foundation.org>,
	"'Linus Torvalds'" <torvalds@...ux-foundation.org>,
	"'Arnd Bergmann'" <arnd@...db.de>
Subject: RE: [PATCH 09/13] unicore: mmu_gather rework



> -----Original Message-----
> From: Peter Zijlstra [mailto:a.p.zijlstra@...llo.nl]
> Sent: Friday, March 04, 2011 8:17 PM
> To: Guan Xuetao
> Cc: linux-kernel@...r.kernel.org; linux-arch@...r.kernel.org; linux-mm@...ck.org; 'Benjamin Herrenschmidt'; 'David Miller'; 'Hugh
> Dickins'; 'Mel Gorman'; 'Nick Piggin'; 'Paul McKenney'; 'Yanmin Zhang'; 'Andrea Arcangeli'; 'Avi Kivity'; 'Thomas Gleixner'; 'Rik van Riel';
> 'Ingo Molnar'; akpm@...ux-foundation.org; 'Linus Torvalds'; Arnd Bergmann
> Subject: RE: [PATCH 09/13] unicore: mmu_gather rework
> 
> On Fri, 2011-03-04 at 19:56 +0800, Guan Xuetao wrote:
> 
> > Thanks Peter.
> > It looks good to me, though it is dependent on your patch set "mm: Preemptible mmu_gather"
> 
> It is indeed, the split-out per arch is purely to ease review. The final
> commit should be a merge of the first 10 patches so as not to break
> bisection.
> 
> > While I have another look to include/asm-generic/tlb.h, I found it is also suitable for unicore32.
> > And so, I rewrite the tlb.h to use asm-generic version, and then your patch set will also work for me.
> 
> Awesome, I notice you're loosing flush_tlb_range() support for this, if
> you're fine with that I'm obviously not going to argue, but if its
> better for your platform to keep doing this we can work on that as well
> as I'm trying to add generic support for range tracking into the generic
> tlb code.
Yes, I think flush_tlb_range() have no effect in unicore32 architecture.
Or perhaps, it is because no optimization, just as you point it below.

> 
> More importantly, you seem to loose your call to flush_cache_range()
> which isn't a NOP on your platform.
IMO, flush_cache_range() is only used in self-modified codes when cachetype is vipt.
So, it could be neglected here.
Perhaps it's wrong.
 
> 
> Furthermore, while arch/unicore32/mm/tlb-ucv2.S is mostly magic to me, I
> see unicore32 is one of the few architectures that actually uses
> vm_flags in flush_tlb_range(). Do you have independent I/D-TLB flushes
> or are you flushing I-cache on VM_EXEC?
We have both independent and global I/D TLB flushes.
And flushing I-cache on VM_EXEC is also needed in self-modified codes, IMO.

> 
> Also, I notice your flush_tlb_range() implementation looks to be a loop
> invalidating individual pages, which I can imagine is cheaper for small
> ranges but large ranges might be better of with a full invalidate. Did
> you think about this?
> 
Yes, it should be optimized.
However, I doubt its effect in unicore32 which has no asid support.

Thanks & Regards.

Guan Xuetao

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/