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From: Dave Young <dyoung@redhat.com>
To: Kazuhito Hagio <k-hagio@ab.jp.nec.com>, anderson@redhat.com
Cc: Mark Rutland <mark.rutland@arm.com>,
	"lijiang@redhat.com" <lijiang@redhat.com>,
	"bhe@redhat.com" <bhe@redhat.com>,
	"ard.biesheuvel@linaro.org" <ard.biesheuvel@linaro.org>,
	"catalin.marinas@arm.com" <catalin.marinas@arm.com>,
	Bhupesh Sharma <bhsharma@redhat.com>,
	"kexec@lists.infradead.org" <kexec@lists.infradead.org>,
	Will Deacon <will.deacon@arm.com>,
	AKASHI Takahiro <takahiro.akashi@linaro.org>,
	James Morse <james.morse@arm.com>, Borislav Petkov <bp@alien8.de>,
	"anderson@redhat.com" <anderson@redhat.com>,
	"linux-arm-kernel@lists.infradead.org"
	<linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH] arm64, vmcoreinfo : Append 'MAX_USER_VA_BITS' and 'MAX_PHYSMEM_BITS' to vmcoreinfo
Date: Wed, 13 Feb 2019 19:15:52 +0800
Message-ID: <20190213111552.GA8265@dhcp-128-65.nay.redhat.com> (raw)
In-Reply-To: <4AE2DC15AC0B8543882A74EA0D43DBEC035683DB@BPXM09GP.gisp.nec.co.jp>

On 02/12/19 at 11:03pm, Kazuhito Hagio wrote:
> 
> On 2/12/2019 2:59 PM, Bhupesh Sharma wrote:
> > BTW, in the makedumpfile enablement patch thread for ARMv8.2 LVA
> > (which I sent out for 52-bit User space VA enablement) (see [0]), Kazu
> > mentioned that the changes look necessary.
> > 
> > [0]. http://lists.infradead.org/pipermail/kexec/2019-February/022431.html
> 
> > > > The increased 'PTRS_PER_PGD' value for such cases needs to be then
> > > > calculated as is done by the underlying kernel (see
> > > > 'arch/arm64/include/asm/pgtable-hwdef.h' for details):
> > > >
> > > > #define PTRS_PER_PGD          (1 << (MAX_USER_VA_BITS - PGDIR_SHIFT))
> 
> Yes, this is the reason why makedumpfile needs the MAX_USER_VA_BITS.
> It is used for pgd_index() also in makedumpfile to walk page tables.
> 
> /* to find an entry in a page-table-directory */
> #define pgd_index(addr)         (((addr) >> PGDIR_SHIFT) & (PTRS_PER_PGD - 1))

Since Dave mentioned crash tool does not need it, but crash should also
travel the pg tables.

If this is really necessary it would be good to describe what will
happen without the patch, eg. some user visible error from an actual test etc.

> 
> Thanks,
> Kazu
> 
> > > >
> > > > Also, note that 'arch/arm64/include/asm/memory.h' defines 'MAX_USER_VA_BITS'
> > > > as 'VA_BITS' in case 'CONFIG_ARM64_USER_VA_BITS_52' is set to 'n':
> > > >
> > > > #ifdef CONFIG_ARM64_USER_VA_BITS_52
> > > > #define MAX_USER_VA_BITS      52
> > > > #else
> > > > #define MAX_USER_VA_BITS      VA_BITS
> > > > #endif
> > > >
> > > > So, makedumpfile will need this symbol exported in vmcore to make the above
> > > > determination.
> > > >
> > > > [0]. http://lists.infradead.org/pipermail/kexec/2019-February/022425.html
> > > >
> > > > Thanks,
> > > > Bhupesh
> > >
> > > Thanks
> > > Dave
> 

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Thread overview: 29+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-01-30 12:23 Bhupesh Sharma
2019-01-30 15:21 ` James Morse
2019-01-30 21:39   ` Bhupesh Sharma
2019-02-04 14:35     ` Bhupesh Sharma
2019-02-04 15:31       ` Robin Murphy
2019-02-12  4:55         ` Bhupesh Sharma
2019-02-12 10:49           ` Robin Murphy
2019-02-04 16:56       ` James Morse
2019-01-31  1:48 ` Dave Young
2019-01-31 10:00   ` Bhupesh Sharma
2019-01-31 14:03   ` Dave Anderson
2019-02-04 16:04   ` Kazuhito Hagio
2019-02-12  5:07     ` Bhupesh Sharma
2019-02-12 10:44       ` Dave Young
2019-02-12 19:59         ` Bhupesh Sharma
2019-02-12 23:03           ` Kazuhito Hagio
2019-02-13 11:15             ` Dave Young [this message]
2019-02-13 18:22               ` James Morse
2019-02-13 19:52                 ` Kazuhito Hagio
2019-02-15 17:34                   ` James Morse
2019-02-15 18:01                     ` Bhupesh Sharma
2019-02-18 15:27                       ` Steve Capper
2019-02-21 16:08                         ` Bhupesh Sharma
2019-02-19 20:47                       ` Kazuhito Hagio
2019-02-21 16:20                         ` Bhupesh Sharma
2019-02-21 16:42                           ` Dave Anderson
2019-02-21 19:02                             ` Kazuhito Hagio
2019-03-01  4:01                               ` Bhupesh Sharma
2019-02-14 19:30                 ` Bhupesh Sharma

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