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From: Richard Henderson <richard.henderson@linaro.org>
To: Peter Maydell <peter.maydell@linaro.org>,
	qemu-arm@nongnu.org, qemu-devel@nongnu.org
Cc: "Alex Bennée" <alex.bennee@linaro.org>
Subject: Re: [Qemu-devel] [PATCH for-4.1?] target/arm: Deliver BKPT/BRK exceptions to correct exception level
Date: Tue, 30 Jul 2019 07:54:18 -0700	[thread overview]
Message-ID: <6788a31f-a46a-0fd3-0513-a2fe558d0703@linaro.org> (raw)
In-Reply-To: <20190730132522.27086-1-peter.maydell@linaro.org>

On 7/30/19 6:25 AM, Peter Maydell wrote:
> Most Arm architectural debug exceptions (eg watchpoints) are ignored
> if the configured "debug exception level" is below the current
> exception level (so for example EL1 can't arrange to get debug exceptions
> for EL2 execution). Exceptions generated by the BRK or BPKT instructions
> are a special case -- they must always cause an exception, so if
> we're executing above the debug exception level then we
> must take them to the current exception level.
> 
> This fixes a bug where executing BRK at EL2 could result in an
> exception being taken at EL1 (which is strictly forbidden by the
> architecture).
> 
> Fixes: https://bugs.launchpad.net/qemu/+bug/1838277
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>

> At this point in the release cycle I'm not sure we should put this
> into 4.1 -- it is definitely a bug but it's not a regression as
> we've been wrong like this for multiple releases, pretty much
> since we put in the debug handling code I suspect.

I'd lean to putting it in, fwiw.


r~


  reply	other threads:[~2019-07-30 14:54 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-07-30 13:25 [Qemu-devel] [PATCH for-4.1?] target/arm: Deliver BKPT/BRK exceptions to correct exception level Peter Maydell
2019-07-30 14:54 ` Richard Henderson [this message]
2019-07-30 15:31 ` Philippe Mathieu-Daudé
2019-07-30 16:41   ` Peter Maydell

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