linux-arm-kernel.lists.infradead.org archive mirror
 help / color / mirror / Atom feed
From: Ard Biesheuvel <ard.biesheuvel@linaro.org>
To: Will Deacon <will@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Mark Brown <broonie@kernel.org>,
	Richard Henderson <richard.henderson@linaro.org>,
	linux-arm-kernel <linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH v10 2/3] arm64: random: Add data to pool from setup_arch()
Date: Wed, 15 Jan 2020 10:22:03 +0100	[thread overview]
Message-ID: <CAKv+Gu9=L6hPSHbvf1qHa7N9hyJ7m7KSYJHBf1em8E0Db_Lghw@mail.gmail.com> (raw)
In-Reply-To: <20200115091615.GA21692@willie-the-truck>

On Wed, 15 Jan 2020 at 10:16, Will Deacon <will@kernel.org> wrote:
>
> On Wed, Jan 15, 2020 at 08:48:46AM +0100, Ard Biesheuvel wrote:
> > On Fri, 10 Jan 2020 at 13:23, Mark Brown <broonie@kernel.org> wrote:
> > >
> > > Since the arm64 ARCH_RANDOM implementation is not available until
> > > cpufeature has determined the system capabilities it can't be used by
> > > the generic random code to initialize the entropy pool for early use.
> > > Instead explicitly add some data to the pool from setup_arch() if the
> > > boot CPU supports v8.5-RNG, this is the point recommended by the generic
> > > code.
> > >
> > > Note that we are only adding data here, it will be mixed into the pool
> > > but won't be credited as entropy. There are currently no suitable
> > > interfaces for that at present - extending the random code to provide
> > > those will be done as a future step. Providing data is better than not
> > > doing so as it will still provide an increase in variation in the output
> > > from the random code and there will be no impact on the rate at which
> > > entropy is credited compared to what we have without this patch.
> > >
> >
> > This is slightly unfortunate, as this way, we lose the ability to use
> > random.trust_cpu=1 to get the entropy credited and initialize CRNG
> > early.
>
> Agreed. Do you think we should wait for that support before merging the
> series? Given that I don't know of any CPUs implementing this extension,
> we can probably afford not to rush this in.
>

In a previous iteration, we did have a functional
arch_get_random_seed_long() early on, which would solve this issue
without even needing a patch like this.

Perhaps Mark (Rutland) can give a recap of his concerns at the time?

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

  reply	other threads:[~2020-01-15  9:22 UTC|newest]

Thread overview: 30+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-10 12:23 [PATCH v10 0/3] ARMv8.5-RNG support Mark Brown
2020-01-10 12:23 ` [PATCH v10 1/3] arm64: Implement archrandom.h for ARMv8.5-RNG Mark Brown
2020-01-14 17:44   ` Will Deacon
2020-01-15  7:40     ` Ard Biesheuvel
2020-01-15  9:16       ` Will Deacon
2020-01-15  9:24         ` Ard Biesheuvel
2020-01-15 11:07           ` Mark Brown
2020-01-15 11:16             ` Will Deacon
2020-01-15 14:26             ` Catalin Marinas
2020-01-16  0:23               ` Richard Henderson
2020-01-16 11:02                 ` Catalin Marinas
2020-01-16 11:10                   ` Ard Biesheuvel
2020-01-16 11:40                     ` Catalin Marinas
2020-01-10 12:23 ` [PATCH v10 2/3] arm64: random: Add data to pool from setup_arch() Mark Brown
2020-01-10 12:35   ` Mark Rutland
2020-01-13 19:09   ` Richard Henderson
2020-01-15  7:48   ` Ard Biesheuvel
2020-01-15  9:16     ` Will Deacon
2020-01-15  9:22       ` Ard Biesheuvel [this message]
2020-01-15 10:11         ` Mark Rutland
2020-01-15 14:01           ` Mark Brown
2020-01-15 12:07       ` Mark Brown
2020-01-15 12:42         ` Will Deacon
2020-01-15 13:36           ` Ard Biesheuvel
2020-01-15 17:04             ` Mark Brown
2020-01-16 11:33               ` Will Deacon
2020-01-15 15:40           ` Mark Brown
2020-01-10 12:23 ` [PATCH v10 3/3] arm64: Use v8.5-RNG entropy for KASLR seed Mark Brown
2020-01-10 12:35   ` Mark Rutland
2020-01-13 19:09   ` Richard Henderson

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='CAKv+Gu9=L6hPSHbvf1qHa7N9hyJ7m7KSYJHBf1em8E0Db_Lghw@mail.gmail.com' \
    --to=ard.biesheuvel@linaro.org \
    --cc=broonie@kernel.org \
    --cc=catalin.marinas@arm.com \
    --cc=linux-arm-kernel@lists.infradead.org \
    --cc=mark.rutland@arm.com \
    --cc=richard.henderson@linaro.org \
    --cc=will@kernel.org \
    /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).