linux-kernel - Re: [PATCH] x86/pat: Fix off-by-one bugs in interval tree search

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Message-ID: <20191201203058.GA82131@gmail.com>
Date:   Sun, 1 Dec 2019 21:30:58 +0100
From:   Ingo Molnar <mingo@...nel.org>
To:     "Kenneth R. Crudup" <kenny@...ix.com>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>, mceier@...il.com,
        Davidlohr Bueso <dave@...olabs.net>,
        kernel test robot <rong.a.chen@...el.com>,
        Davidlohr Bueso <dbueso@...e.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Borislav Petkov <bp@...en8.de>,
        LKML <linux-kernel@...r.kernel.org>, lkp@...ts.01.org
Subject: Re: [PATCH] x86/pat: Fix off-by-one bugs in interval tree search


* Kenneth R. Crudup <kenny@...ix.com> wrote:

> > > write-combining @ 0x604a800000-0x604b000000
> > > uncached-minus @ 0x604b100000-0x604b110000
> 
> > This WC region was probably unaffected by the bug.
> 
> For my education, and for completeness' sake, is there a proc/sys entry
> that would tell me which device/module has reserved which PAT region?

Not that I know of :-/

I suspect you could run the attached patch and run:

  dmesg | grep -i 'x86/pat'

To see all the ioremap() activities, with a symbolic name of the caller printed.

I'm quite sure 0x604a800000 will be among them, pointing to somewhere 
like i915_vma_pin_iomap(), ggtt_init_hw() or ggtt_probe_common() in the 
i915 GPU driver?

Another possibility is that this is the FB framebuffer, mapped by 
efifb_probe() or so?

Patch is untested though. :-)

Thanks,

	Ingo

=================>

 arch/x86/mm/ioremap.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/x86/mm/ioremap.c b/arch/x86/mm/ioremap.c
index 1ff9c2030b4f..2f0a4f99471a 100644
--- a/arch/x86/mm/ioremap.c
+++ b/arch/x86/mm/ioremap.c
@@ -166,6 +166,8 @@ __ioremap_caller(resource_size_t phys_addr, unsigned long size,
 	int retval;
 	void __iomem *ret_addr;
 
+	printk("# x86/pat: ioremap(%016Lx, %08lx, pcm: %d), caller: %pS\n", phys_addr, size, pcm, caller);
+
 	/* Don't allow wraparound or zero size */
 	last_addr = phys_addr + size - 1;
 	if (!size || last_addr < phys_addr)