From: Mark Brown <broonie@kernel•org>
To: Suzuki K Poulose <suzuki.poulose@arm•com>
Cc: Catalin Marinas <catalin.marinas@arm•com>,
Will Deacon <will@kernel•org>,
linux-arm-kernel@lists•infradead.org
Subject: Re: [PATCH v2 2/2] arm64: Don't use KPTI where we have E0PD
Date: Wed, 9 Oct 2019 18:52:05 +0100 [thread overview]
Message-ID: <20191009175205.GN2036@sirena.org.uk> (raw)
In-Reply-To: <6834da7b-553c-2ad3-9b05-25ca982252e9@arm.com>
[-- Attachment #1.1: Type: text/plain, Size: 1600 bytes --]
On Tue, Sep 24, 2019 at 10:13:18AM +0100, Suzuki K Poulose wrote:
> On 16/08/2019 13:10, Mark Brown wrote:
> > We definitely need some variable I think, and I think you're right that
> > making the decision on the boot CPU would simplify things a lot. The
> relocating the kernel. So, we may be able to perform "raw cpuid check" on
> the boot CPU with MMU turned on, before we re-write the pagetables for KASLR
> displacement and nG if that is needed (by maybe updating SWWAPPER_MMU_FLAGS) for
> the boot CPU and store this information somewhere. Thus we may be able to
> avoid another re-write of the pagetables after we have booted the secondaries.
The boot CPU is straightforward, there is only an issue on the
secondaries where IIRC the rewrite code needs some updates as we
get left with non-global mappings lying around.
> Discussing this with Catalin, he suggests to use a variable for the status
> of "nG" flag for PTE/PMD_MAYBE_NG, to avoid calling the helper function
> all the time. By using the per-CPU check we can make sure the flag is uptodate.
That was the discussion about the variable above. We need one
for non-optimization reasons anyway since we can't rely on
checking the state on the current CPU.
> Also, we can continue to fail the hotplugged CPUs if we detect that the
> pagetables are Global and the new CPU requires nG (for heterogeneous
> systems).
There's no continuing to reject those CPUs unfortunately, we
don't reject anything currently. Any such systems would
experience a regression when moving to a kernel where E0PD is
enabled which doesn't seem ideal.
[-- Attachment #1.2: signature.asc --]
[-- Type: application/pgp-signature, Size: 488 bytes --]
[-- Attachment #2: Type: text/plain, Size: 176 bytes --]
_______________________________________________
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:[~2019-10-09 17:52 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-14 18:31 [PATCH v2 0/2] arm64: E0PD support Mark Brown
2019-08-14 18:31 ` [PATCH v2 1/2] arm64: Add initial support for E0PD Mark Brown
2019-10-10 16:13 ` Mark Rutland
2019-10-11 11:17 ` Mark Brown
2019-10-11 11:40 ` Will Deacon
2019-10-11 12:57 ` Mark Rutland
2019-10-11 12:58 ` Catalin Marinas
2019-10-11 13:46 ` Mark Brown
2019-08-14 18:31 ` [PATCH v2 2/2] arm64: Don't use KPTI where we have E0PD Mark Brown
2019-08-15 16:35 ` Will Deacon
2019-08-15 18:00 ` Mark Brown
2019-08-16 11:31 ` Mark Brown
2019-08-16 10:24 ` Catalin Marinas
2019-08-16 12:10 ` Mark Brown
2019-09-24 9:13 ` Suzuki K Poulose
2019-10-09 17:52 ` Mark Brown [this message]
2019-10-10 10:24 ` Suzuki K Poulose
2019-10-10 16:04 ` Mark Brown
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=20191009175205.GN2036@sirena.org.uk \
--to=broonie@kernel$(echo .)org \
--cc=catalin.marinas@arm$(echo .)com \
--cc=linux-arm-kernel@lists$(echo .)infradead.org \
--cc=suzuki.poulose@arm$(echo .)com \
--cc=will@kernel$(echo .)org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
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