From: Richard Henderson <richard.henderson@linaro.org>
To: Rebecca Cran <rebecca@nuviainc.com>, qemu-devel@nongnu.org
Cc: Peter Maydell <peter.maydell@linaro.org>
Subject: Re: [PATCH 1/2] target/arm: add support for FEAT_DIT, Data Independent Timing
Date: Fri, 11 Dec 2020 13:51:40 -0600 [thread overview]
Message-ID: <46d7b991-d305-bd2f-91f9-cdc2ee1e73ce@linaro.org> (raw)
In-Reply-To: <284b9f4e-55b7-81a3-f1c5-7f7b6d0c9784@nuviainc.com>
On 12/11/20 1:33 PM, Rebecca Cran wrote:
> Is the comment in target/arm/op_helper.c:397 still relevant?
>
> uint32_t HELPER(cpsr_read)(CPUARMState *env)
> {
> /*
> * We store the ARMv8 PSTATE.SS bit in env->uncached_cpsr.
> * This is convenient for populating SPSR_ELx, but must be
> * hidden from aarch32 mode, where it is not visible.
> *
> * TODO: ARMv8.4-DIT -- need to move SS somewhere else.
> */
> return cpsr_read(env) & ~(CPSR_EXEC | PSTATE_SS);
> }
I forgot about this. So we can't "just" store DIT in uncached_cpsr.
I'll let Peter weigh in, but I think it makes sense to move the SS bit
somewhere else (e.g. env->pstate) and merge it into SPSR_ELx upon interrupt.
While what we're doing here is convenient, it's not architectural, and it would
be better to follow GetPSRFromPSTATE pseudocode.
r~
next prev parent reply other threads:[~2020-12-11 19:59 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-11 5:13 [PATCH 0/2] target/arm: Add support for DIT (Data Independent Timing) Rebecca Cran
2020-12-11 5:13 ` [PATCH 1/2] target/arm: add support for FEAT_DIT, Data Independent Timing Rebecca Cran
2020-12-11 14:08 ` Richard Henderson
2020-12-11 19:33 ` Rebecca Cran
2020-12-11 19:51 ` Richard Henderson [this message]
2020-12-11 21:37 ` Peter Maydell
2020-12-14 18:11 ` Rebecca Cran
2020-12-14 18:48 ` Peter Maydell
2020-12-11 5:13 ` [PATCH 2/2] target/arm: Set ID_AA64PFR0.DIT and ID_PFR0.DIT to 1 for "max" AA64 CPU Rebecca Cran
2020-12-11 14:09 ` 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=46d7b991-d305-bd2f-91f9-cdc2ee1e73ce@linaro.org \
--to=richard.henderson@linaro.org \
--cc=peter.maydell@linaro.org \
--cc=qemu-devel@nongnu.org \
--cc=rebecca@nuviainc.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).