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From: Thomas Gleixner <tglx@linutronix.de>
To: Steven Price <steven.price@arm.com>
Cc: "Mark Rutland" <mark.rutland@arm.com>,
	x86@kernel.org, "Arnd Bergmann" <arnd@arndb.de>,
	"Ard Biesheuvel" <ard.biesheuvel@linaro.org>,
	"Peter Zijlstra" <peterz@infradead.org>,
	"Catalin Marinas" <catalin.marinas@arm.com>,
	"Dave Hansen" <dave.hansen@linux.intel.com>,
	linux-kernel@vger.kernel.org, linux-mm@kvack.org,
	"Jérôme Glisse" <jglisse@redhat.com>,
	"Ingo Molnar" <mingo@redhat.com>,
	"Borislav Petkov" <bp@alien8.de>,
	"Andy Lutomirski" <luto@kernel.org>,
	"H. Peter Anvin" <hpa@zytor.com>,
	"James Morse" <james.morse@arm.com>,
	"Will Deacon" <will@kernel.org>,
	"Andrew Morton" <akpm@linux-foundation.org>,
	linux-arm-kernel@lists.infradead.org, "Liang,
	Kan" <kan.liang@linux.intel.com>
Subject: Re: [PATCH v9 00/21] Generic page walk and ptdump
Date: Wed, 24 Jul 2019 15:57:33 +0200 (CEST)
Message-ID: <alpine.DEB.2.21.1907241541570.1791@nanos.tec.linutronix.de> (raw)
In-Reply-To: <e108b8a6-deca-e69c-b338-52a98b14be86@arm.com>

On Wed, 24 Jul 2019, Steven Price wrote:
> On 23/07/2019 11:16, Mark Rutland wrote:
> > Are there any visible changes to the arm64 output?
> 
> arm64 output shouldn't change. I've confirmed that "efi_page_tables" is
> identical on a Juno before/after the change. "kernel_page_tables"
> obviously will vary depending on the exact layout of memory, but the
> format isn't changed.
> 
> x86 output does change due to patch 14. In this case the change is
> removing the lines from the output of the form...
> 
> > 0xffffffff84800000-0xffffffffa0000000         440M                               pmd
> 
> ...which are unpopulated areas of the memory map. Populated lines which
> have attributes are unchanged.

Having the hole size and the level in the dump is a very conveniant thing.

Right now we have:

0xffffffffc0427000-0xffffffffc042b000          16K     ro                     NX pte
0xffffffffc042b000-0xffffffffc042e000          12K     RW                     NX pte
0xffffffffc042e000-0xffffffffc042f000           4K                               pte
0xffffffffc042f000-0xffffffffc0430000           4K     ro                     x  pte
0xffffffffc0430000-0xffffffffc0431000           4K     ro                     NX pte
0xffffffffc0431000-0xffffffffc0433000           8K     RW                     NX pte
0xffffffffc0433000-0xffffffffc0434000           4K                               pte
0xffffffffc0434000-0xffffffffc0436000           8K     ro                     x  pte
0xffffffffc0436000-0xffffffffc0438000           8K     ro                     NX pte
0xffffffffc0438000-0xffffffffc043a000           8K     RW                     NX pte
0xffffffffc043a000-0xffffffffc043f000          20K                               pte
0xffffffffc043f000-0xffffffffc0444000          20K     ro                     x  pte
0xffffffffc0444000-0xffffffffc0447000          12K     ro                     NX pte
0xffffffffc0447000-0xffffffffc0449000           8K     RW                     NX pte
0xffffffffc0449000-0xffffffffc044f000          24K                               pte
0xffffffffc044f000-0xffffffffc0450000           4K     ro                     x  pte
0xffffffffc0450000-0xffffffffc0451000           4K     ro                     NX pte
0xffffffffc0451000-0xffffffffc0453000           8K     RW                     NX pte
0xffffffffc0453000-0xffffffffc0458000          20K                               pte
0xffffffffc0458000-0xffffffffc0459000           4K     ro                     x  pte
0xffffffffc0459000-0xffffffffc045b000           8K     ro                     NX pte

with your change this becomes:

0xffffffffc0427000-0xffffffffc042b000          16K     ro                     NX pte
0xffffffffc042b000-0xffffffffc042e000          12K     RW                     NX pte
0xffffffffc042f000-0xffffffffc0430000           4K     ro                     x  pte
0xffffffffc0430000-0xffffffffc0431000           4K     ro                     NX pte
0xffffffffc0431000-0xffffffffc0433000           8K     RW                     NX pte
0xffffffffc0434000-0xffffffffc0436000           8K     ro                     x  pte
0xffffffffc0436000-0xffffffffc0438000           8K     ro                     NX pte
0xffffffffc0438000-0xffffffffc043a000           8K     RW                     NX pte
0xffffffffc043f000-0xffffffffc0444000          20K     ro                     x  pte
0xffffffffc0444000-0xffffffffc0447000          12K     ro                     NX pte
0xffffffffc0447000-0xffffffffc0449000           8K     RW                     NX pte
0xffffffffc044f000-0xffffffffc0450000           4K     ro                     x  pte
0xffffffffc0450000-0xffffffffc0451000           4K     ro                     NX pte
0xffffffffc0451000-0xffffffffc0453000           8K     RW                     NX pte
0xffffffffc0458000-0xffffffffc0459000           4K     ro                     x  pte
0xffffffffc0459000-0xffffffffc045b000           8K     ro                     NX pte

which is 5 lines less, but a pain to figure out the size of the holes. And
it becomes even more painful when the holes go across different mapping
levels.

From your 14/N changelog:

> This keeps the output shorter and will help with a future change

I don't care about shorter at all. It's debug information.

> switching to using the generic page walk code as we no longer care about
> the 'level' that the page table holes are at.

I really do not understand why you think that WE no longer care about the
level (and the size) of the holes. I assume that WE is pluralis majestatis
and not meant to reflect the opinion of you and everyone else.

I have no idea whether you ever had to do serious work with PT dump, but I
surely have at various occasions including the PTI mess and I definitely
found the size and the level information from holes very useful.

Thanks,

	tglx






  reply index

Thread overview: 62+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-07-22 15:41 Steven Price
2019-07-22 15:41 ` [PATCH v9 01/21] arc: mm: Add p?d_leaf() definitions Steven Price
2019-07-22 15:41 ` [PATCH v9 02/21] arm: " Steven Price
2019-07-22 15:41 ` [PATCH v9 03/21] arm64: " Steven Price
2019-07-22 15:41 ` [PATCH v9 04/21] mips: " Steven Price
2019-07-22 21:47   ` Paul Burton
2019-07-24 13:03     ` Steven Price
2019-07-22 15:41 ` [PATCH v9 05/21] powerpc: " Steven Price
2019-07-22 15:41 ` [PATCH v9 06/21] riscv: " Steven Price
2019-07-22 15:41 ` [PATCH v9 07/21] s390: " Steven Price
2019-07-22 15:41 ` [PATCH v9 08/21] sparc: " Steven Price
2019-07-22 15:41 ` [PATCH v9 09/21] x86: " Steven Price
2019-07-22 15:41 ` [PATCH v9 10/21] mm: Add generic p?d_leaf() macros Steven Price
2019-07-23  9:41   ` Mark Rutland
2019-07-24 13:48     ` Steven Price
2019-07-28 11:44     ` Anshuman Khandual
2019-07-29 11:38       ` Steven Price
2019-08-01  6:09         ` Anshuman Khandual
2019-08-01 12:22           ` Steven Price
2019-07-29 12:50       ` Mark Rutland
2019-08-01  6:13         ` Anshuman Khandual
2019-07-22 15:42 ` [PATCH v9 11/21] mm: pagewalk: Add p4d_entry() and pgd_entry() Steven Price
2019-07-23 10:14   ` Mark Rutland
2019-07-24 13:53     ` Steven Price
2019-07-24 14:09       ` Mark Rutland
2019-07-28 12:33   ` Anshuman Khandual
2019-07-29 12:17     ` Steven Price
2019-07-22 15:42 ` [PATCH v9 12/21] mm: pagewalk: Allow walking without vma Steven Price
2019-07-28 14:20   ` Anshuman Khandual
2019-07-29 12:29     ` Steven Price
2019-08-01  6:41       ` Anshuman Khandual
2019-07-22 15:42 ` [PATCH v9 13/21] mm: pagewalk: Add test_p?d callbacks Steven Price
2019-07-28 13:41   ` Anshuman Khandual
2019-07-29 12:34     ` Steven Price
2019-07-22 15:42 ` [PATCH v9 14/21] x86: mm: Don't display pages which aren't present in debugfs Steven Price
2019-07-22 15:42 ` [PATCH v9 15/21] x86: mm: Point to struct seq_file from struct pg_state Steven Price
2019-07-22 15:42 ` [PATCH v9 16/21] x86: mm+efi: Convert ptdump_walk_pgd_level() to take a mm_struct Steven Price
2019-07-22 15:42 ` [PATCH v9 17/21] x86: mm: Convert ptdump_walk_pgd_level_debugfs() to take an mm_struct Steven Price
2019-07-22 15:42 ` [PATCH v9 18/21] x86: mm: Convert ptdump_walk_pgd_level_core() " Steven Price
2019-07-22 15:42 ` [PATCH v9 19/21] mm: Add generic ptdump Steven Price
2019-07-23  9:57   ` Mark Rutland
2019-07-24 16:36     ` Steven Price
2019-07-29  2:59   ` Anshuman Khandual
2019-07-29 13:56     ` Steven Price
2019-07-22 15:42 ` [PATCH v9 20/21] x86: mm: Convert dump_pagetables to use walk_page_range Steven Price
2019-07-22 15:42 ` [PATCH v9 21/21] arm64: mm: Convert mm/dump.c to use walk_page_range() Steven Price
2019-07-23  6:39 ` [PATCH v9 00/21] Generic page walk and ptdump Anshuman Khandual
2019-07-24 13:35   ` Steven Price
2019-07-25  9:09     ` Anshuman Khandual
2019-07-25  9:30       ` Will Deacon
2019-07-26  6:03         ` Anshuman Khandual
2019-07-25 10:15       ` Steven Price
2019-07-23 10:16 ` Mark Rutland
2019-07-24 13:35   ` Steven Price
2019-07-24 13:57     ` Thomas Gleixner [this message]
2019-07-24 14:07       ` Mark Rutland
2019-07-24 14:18       ` Steven Price
2019-07-24 14:37         ` Thomas Gleixner
2019-07-28 11:20 ` Anshuman Khandual
2019-07-29 11:32   ` Steven Price
2019-07-31  9:27     ` Sven Schnelle
2019-07-31 11:18       ` Steven Price

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