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From: Arjan van de Ven <arjan@infradead.org>
To: Pekka Paalanen <pq@iki.fi>
Cc: Ingo Molnar <mingo@elte.hu>, Pekka Paalanen <pq@iki.fi>,
	Harvey Harrison <harvey.harrison@gmail.com>,
	linux-kernel@vger.kernel.org,
	Peter Zijlstra <a.p.zijlstra@chello.nl>
Subject: Re: [RFC PATCH v2] x86: mmiotrace - trace memory mapped IO
Date: Thu, 31 Jan 2008 08:29:06 -0800	[thread overview]
Message-ID: <20080131082906.6a1befba@laptopd505.fenrus.org> (raw)
In-Reply-To: <20080131181630.10cb1eac@daedalus.pq.iki.fi>

On Thu, 31 Jan 2008 18:16:30 +0200
Pekka Paalanen <pq@iki.fi> wrote:

> > > could you please send us a patch for the whole mmiotrace
> > > kernel-side feature, so that we can have a look at the general
> > > structure of this? (and the interaction with change_page_attr(),
> > > etc.) Even if it's not functional (and wont even build/boot) at
> > > the moment. Thanks,
> 
> And here's mmiotrace. This works for me (amd64), but not for a test
> user who has 32-bit x86. We have not had the chance to debug it yet.
> The symptom is "everything locked up" after insmodding
> testmmiotrace.ko, targeting the mid-point of his VRAM. And there's
> the "undefined symbol init_mm" problem on 32-bit, but we just put the
> export back in (not included in these patches).
> 
> No-one has tried this on SMP. I have a Core 2 Duo laptop where I will
> test this when I get the chance.

 +static void print_pte(unsigned long address)
> +{
> +	pgd_t *pgd = pgd_offset_k(address);
> +	pud_t *pud = pud_offset(pgd, address);
> +	pmd_t *pmd = pmd_offset(pud, address);
> +	if (pmd_large(*pmd)) {
> +		printk(KERN_EMERG MODULE_NAME ": 4MB pages are not "
> +						"currently
> supported: %lx\n",
> +						address);
> +		BUG();
> +	}
> +	printk(KERN_DEBUG MODULE_NAME ": pte for 0x%lx: 0x%lx
> 0x%lx\n",
> +		address,
> +		pte_val(*pte_offset_kernel(pmd, address)),
> +		pte_val(*pte_offset_kernel(pmd, address)) &
> _PAGE_PRESENT); +}

ok this wants to use some of the page_address() and other helpers from pageattr.c;
that should be easy to solve during integration
(I can even see a more generic version of this function moving there)


> +/* file_create() callback.  Creates relay file in debugfs. */
> +static struct dentry *create_buf_file_handler(const char *filename,
> +						struct dentry
> *parent,
> +						int mode,
> +						struct rchan_buf
> *buf,
> +						int *is_global)
> +{
> +	struct dentry *buf_file;
> +
> +	mmio_fops.read = relay_file_operations.read;
> +	mmio_fops.open = relay_file_operations.open;
> +	mmio_fops.poll = relay_file_operations.poll;
> +	mmio_fops.mmap = relay_file_operations.mmap;
> +	mmio_fops.release = relay_file_operations.release;
> +	mmio_fops.splice_read = relay_file_operations.splice_read;

can't we do this at compile time?


> +
> +void __iomem *ioremap_cache_trace(unsigned long offset, unsigned
> long size) +{
> +	void __iomem *p = ioremap_cache(offset, size);
> +	printk(KERN_DEBUG MODULE_NAME ": ioremap_cache(0x%lx, 0x%lx)
> = %p\n",
> +							offset,
> size, p);
> +	ioremap_trace_core(offset, size, p);
> +	return p;
> +}
> +EXPORT_SYMBOL(ioremap_cache_trace);
> +
> +void __iomem *ioremap_nocache_trace(unsigned long offset, unsigned
> long size) +{
> +	void __iomem *p = ioremap_nocache(offset, size);
> +	printk(KERN_DEBUG MODULE_NAME ": ioremap_nocache(0x%lx,
> 0x%lx) = %p\n",
> +							offset,
> size, p);
> +	ioremap_trace_core(offset, size, p);
> +	return p;
> +}
> +EXPORT_SYMBOL(ioremap_nocache_trace);

I would rather keep the split I think and make the trace call explicit

or.. even nicer, we could go fancy and allow the mmio tracer to "subscribe"
to, say, a PCI bar, and auto-enable tracing when the bar gets ioremap'd



about the isntruction decoding.. would be nice if we can share that with kvm
so that we can debug that stuff once ;-)


other than that I think the code is quite nice already, seems getting this merge
ready isn't going to be an enormous deal in terms of complexity

  reply	other threads:[~2008-01-31 16:29 UTC|newest]

Thread overview: 43+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-01-27 16:52 [PATCH] x86: Add a list for custom page fault handlers Pekka Paalanen
2008-01-27 17:55 ` [RFC PATCH] x86: mmiotrace - trace memory mapped IO Pekka Paalanen
2008-01-30 22:39   ` Pekka Paalanen
2008-01-27 19:29 ` [PATCH] x86: Add a list for custom page fault handlers Ingo Molnar
2008-01-27 21:03 ` Peter Zijlstra
2008-01-30  2:28 ` Harvey Harrison
2008-01-30  2:34   ` Harvey Harrison
2008-01-30 18:08     ` Pekka Paalanen
2008-01-31 15:07       ` Ingo Molnar
2008-01-31 16:02         ` [PATCH v2] " Pekka Paalanen
2008-01-31 16:15           ` Arjan van de Ven
2008-02-03  6:55             ` Pekka Paalanen
2008-02-03  7:03               ` Ingo Molnar
2008-02-03 21:40                 ` Pekka Paalanen
2008-02-05 20:28                 ` [PATCH 1/4] x86 mmiotrace: use lookup_address() Pekka Paalanen
2008-02-05 20:30                   ` [PATCH 2/4] x86 mmiotrace: fix relay-buffer-full flag for SMP Pekka Paalanen
2008-02-05 20:44                     ` Eric Dumazet
2008-02-05 21:14                       ` Pekka Paalanen
2008-02-05 21:35                         ` Eric Dumazet
2008-02-09 17:53                           ` [PATCH] x86 mmiotrace: Use percpu instead of arrays Pekka Paalanen
2008-02-05 20:31                   ` [PATCH 3/4] x86 mmiotrace: comment about user space ABI Pekka Paalanen
2008-02-05 20:39                   ` [PATCH 4/4] x86 mmiotrace: move files into arch/x86/mm/ Pekka Paalanen
2008-02-06  3:02                     ` Randy Dunlap
2008-02-09 11:21                       ` Pekka Paalanen
2008-02-07 12:53                     ` Ingo Molnar
2008-02-07 12:56                       ` Christoph Hellwig
2008-02-09 17:52                         ` [RFC PATCH] x86: explicit call to mmiotrace in do_page_fault() Pekka Paalanen
2008-02-09 18:01                           ` Arjan van de Ven
2008-02-09 18:23                             ` Pekka Paalanen
2008-02-09 18:56                               ` Pekka Enberg
2008-02-09 19:11                                 ` Pekka Paalanen
2008-02-09 19:19                                   ` Pekka Enberg
2008-02-09 18:39                             ` Peter Zijlstra
2008-02-09 18:39                           ` Peter Zijlstra
2008-02-10 18:05                             ` [RFC PATCH v2] " Pekka Paalanen
2008-02-11  2:12                               ` Pavel Roskin
2008-02-11 18:04                                 ` Pekka Paalanen
2008-02-06  5:00                   ` [PATCH 1/4] x86 mmiotrace: use lookup_address() Christoph Hellwig
2008-02-07 12:52                     ` Ingo Molnar
2008-01-31 16:16           ` [RFC PATCH v2] x86: mmiotrace - trace memory mapped IO Pekka Paalanen
2008-01-31 16:29             ` Arjan van de Ven [this message]
2008-02-03  7:21               ` Pekka Paalanen
2008-01-30 18:20 ` [PATCH] x86: Add a list for custom page fault handlers Arjan van de Ven

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