From: Bhupesh Sharma <bhsharma@redhat.com>
To: Steve Capper <steve.capper@arm.com>,
linux-arm-kernel@lists.infradead.org
Cc: crecklin@redhat.com, Ard Biesheuvel <ard.biesheuvel@linaro.org>,
marc.zyngier@arm.com, Catalin Marinas <catalin.marinas@arm.com>,
Suzuki K Poulose <suzuki.poulose@arm.com>,
will.deacon@arm.com, Dave Anderson <anderson@redhat.com>,
James Morse <james.morse@arm.com>,
Bhupesh SHARMA <bhupesh.linux@gmail.com>
Subject: Re: [PATCH 0/9] 52-bit kernel + user VAs
Date: Wed, 3 Apr 2019 13:39:36 +0530 [thread overview]
Message-ID: <0b20407f-71ab-165b-2fce-ae8c43fc3316@redhat.com> (raw)
In-Reply-To: <20190218170245.14915-1-steve.capper@arm.com>
Hi Steve,
On 02/18/2019 10:32 PM, Steve Capper wrote:
> This patch series adds support for 52-bit kernel VAs using some of the
> machinery already introduced by the 52-bit userspace VA code in 5.0.
>
> As 52-bit virtual address support is an optional hardware feature,
> software support for 52-bit kernel VAs needs to be deduced at early boot
> time. If HW support is not available, the kernel falls back to 48-bit.
>
> A significant proportion of this series focuses on "de-constifying"
> VA_BITS related constants.
>
> In order to allow for a KASAN shadow that changes size at boot time, one
> must fix the KASAN_SHADOW_END for both 48 & 52-bit VAs and "grow" the
> start address. Also, it is highly desirable to maintain the same
> function addresses in the kernel .text between VA sizes. Both of these
> requirements necessitate us to flip the kernel address space halves s.t.
> the direct linear map occupies the lower addresses.
>
> One obvious omission is 52-bit kernel VA + 48-bit userspace VA which I
> can add with some more #ifdef'ery if needed.
Thanks for the patchset.
I did some work on the user-space side to see how user-space tools like
makedumpfile and kexec-tools are affected by these changes. I see that
Dave Anderson (in Cc) also did some work on crash-utility side [0] to
have the basic framework in place to have the user-space tools work with
the inverted memory map.
I have a couple of concerns regarding:
1. VA_BITS_ACTUAL, and how user-space gets to know its value.
2. Overall bits that we need to be aware in user-space now to address
the following combinations of address space (phew ..):
a) 48-bit Kernel VA + 48-bit User-space VA + 48-bit PA
b) 48-bit Kernel VA + 48-bit User-space VA + 52-bit PA
c) 48-bit Kernel VA + 52-bit User-space VA + 52-bit PA
d) 52-bit Kernel VA + 52-bit User-space VA + 52-bit PA
e) 52-bit Kernel VA + 48-bit User-space VA + 52-bit PA (is this even
used-somewhere? Not sure but James [in Cc] had some queries on this [1].
Personally, I am not aware of any users of this combination).
I have added detailed comments/concerns in individual patches in mails
to follow regarding the above points.
[0].
https://github.com/crash-utility/crash/commit/b0b3ef2eda543413762b32710b8a63dd9ed55de5
[1]. http://lists.infradead.org/pipermail/kexec/2019-April/022729.html
Thanks,
Bhupesh
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2019-04-03 8:09 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-02-18 17:02 [PATCH 0/9] 52-bit kernel + user VAs Steve Capper
2019-02-18 17:02 ` [PATCH 1/9] arm/arm64: KVM: Formalise end of direct linear map Steve Capper
2019-02-18 17:02 ` [PATCH 2/9] arm64: mm: Flip kernel VA space Steve Capper
2019-04-03 11:44 ` Bhupesh Sharma
2019-02-18 17:02 ` [PATCH 3/9] arm64: kasan: Switch to using KASAN_SHADOW_OFFSET Steve Capper
2019-02-18 17:02 ` [PATCH 4/9] arm64: mm: Replace fixed map BUILD_BUG_ON's with BUG_ON's Steve Capper
2019-02-18 17:02 ` [PATCH 5/9] arm64: dump: Make kernel page table dumper dynamic again Steve Capper
2019-02-18 17:02 ` [PATCH 6/9] arm64: mm: Introduce VA_BITS_MIN Steve Capper
2019-02-18 17:02 ` [PATCH 7/9] arm64: mm: Introduce VA_BITS_ACTUAL Steve Capper
2019-02-18 17:02 ` [PATCH 8/9] arm64: mm: Logic to make offset_ttbr1 conditional Steve Capper
2019-04-03 11:26 ` Bhupesh Sharma
2019-02-18 17:02 ` [PATCH 9/9] arm64: mm: Introduce 52-bit Kernel VAs Steve Capper
2019-03-25 18:17 ` Catalin Marinas
2019-02-19 12:13 ` [PATCH 0/9] 52-bit kernel + user VAs Ard Biesheuvel
2019-02-19 12:48 ` Will Deacon
2019-02-19 12:51 ` Ard Biesheuvel
2019-02-19 13:01 ` Will Deacon
2019-02-19 13:15 ` Ard Biesheuvel
2019-02-19 13:56 ` Steve Capper
2019-02-19 16:18 ` Ard Biesheuvel
2019-02-26 17:30 ` Steve Capper
2019-02-26 20:17 ` Ard Biesheuvel
2019-02-28 10:35 ` Steve Capper
2019-02-28 11:22 ` Ard Biesheuvel
2019-02-28 11:45 ` Steve Capper
2019-03-25 18:38 ` Catalin Marinas
2019-03-25 20:32 ` Ard Biesheuvel
2019-04-03 8:09 ` Bhupesh Sharma [this message]
2019-05-03 14:57 ` Steve Capper
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=0b20407f-71ab-165b-2fce-ae8c43fc3316@redhat.com \
--to=bhsharma@redhat.com \
--cc=anderson@redhat.com \
--cc=ard.biesheuvel@linaro.org \
--cc=bhupesh.linux@gmail.com \
--cc=catalin.marinas@arm.com \
--cc=crecklin@redhat.com \
--cc=james.morse@arm.com \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=marc.zyngier@arm.com \
--cc=steve.capper@arm.com \
--cc=suzuki.poulose@arm.com \
--cc=will.deacon@arm.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).