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Re: [Qemu-arm] [PATCH for-4.1?] target/arm: Deliver BKPT/BRK exceptions

From: Richard Henderson
Subject: Re: [Qemu-arm] [PATCH for-4.1?] target/arm: Deliver BKPT/BRK exceptions to correct exception level
Date: Tue, 30 Jul 2019 07:54:18 -0700
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0

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 <address@hidden>

Reviewed-by: Richard Henderson <address@hidden>

> 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.


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