From: Ard Biesheuvel <ardb@kernel.org>
To: Peter Maydell <peter.maydell@linaro.org>
Cc: qemu-devel@nongnu.org, "Philippe Mathieu-Daudé" <f4bug@amsat.org>,
"Richard Henderson" <richard.henderson@linaro.org>
Subject: Re: [PATCH] target/arm: Use signed quantity to represent VMSAv8-64 translation level
Date: Tue, 22 Nov 2022 16:49:48 +0100 [thread overview]
Message-ID: <CAMj1kXEwe48nwV3QkrWLx5=+_qgqwRqW8+otz890WteNvJQtSA@mail.gmail.com> (raw)
In-Reply-To: <CAFEAcA-_D8JnCPEVt6pmAPGeB3cEro+n4Hk0hxoyVD0zToz+HA@mail.gmail.com>
On Tue, 22 Nov 2022 at 14:21, Peter Maydell <peter.maydell@linaro.org> wrote:
>
> On Mon, 21 Nov 2022 at 19:02, Ard Biesheuvel <ardb@kernel.org> wrote:
> >
> > On Mon, 21 Nov 2022 at 19:51, Peter Maydell <peter.maydell@linaro.org> wrote:
> > >
> > > On Mon, 21 Nov 2022 at 17:43, Ard Biesheuvel <ardb@kernel.org> wrote:
> > > >
> > > > The LPA2 extension implements 52-bit virtual addressing for 4k and 16k
> > > > translation granules, and for the former, this means an additional level
> > > > of translation is needed. This means we start counting at -1 instead of
> > > > 0 when doing a walk, and so 'level' is now a signed quantity, and should
> > > > be typed as such. So turn it from uint32_t into int32_t.
> > > >
> > >
> > > Does this cause any visible wrong behaviour, or is it just
> > > a cleanup thing ?
> > >
> >
> > No, 5 level paging is completely broken because of this, given that
> > the 'level < 3' tests give the wrong result for (uint32_t)-1
>
> Right, thanks. This seems like a bug worth fixing for 7.2.
>
Indeed. And the other patch I sent is needed too if you want to run with LPA2
'target/arm: Limit LPA2 effective output address when TCR.DS == 0'
In case it is useful, I have a WIP kernel branch here which can be
built with 52-bit virtual addressing for 4k or 16k pages.
https://git.kernel.org/pub/scm/linux/kernel/git/ardb/linux.git/log/?h=arm64-4k-lpa2
> We should make 'uint32_t startlevel' also an int32_t
> for consistency, I think, given that it is also sometimes
> negative, though in that case it doesn't get used in any
> comparisons so it's not going to cause wrong behaviour.
>
Indeed. I'll send a v2 and fold that in.
prev parent reply other threads:[~2022-11-22 15:50 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-11-21 17:43 [PATCH] target/arm: Use signed quantity to represent VMSAv8-64 translation level Ard Biesheuvel
2022-11-21 18:51 ` Peter Maydell
2022-11-21 19:02 ` Ard Biesheuvel
2022-11-22 13:20 ` Peter Maydell
2022-11-22 15:49 ` Ard Biesheuvel [this message]
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