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Re: [PATCH v2 10/21] target/arm: Stop assuming DBGDIDR always exists

From: Richard Henderson
Subject: Re: [PATCH v2 10/21] target/arm: Stop assuming DBGDIDR always exists
Date: Fri, 14 Feb 2020 12:15:21 -0800
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.4.1

On 2/14/20 9:51 AM, Peter Maydell wrote:
> The AArch32 DBGDIDR defines properties like the number of
> breakpoints, watchpoints and context-matching comparators.  On an
> AArch64 CPU, the register may not even exist if AArch32 is not
> supported at EL1.
> Currently we hard-code use of DBGDIDR to identify the number of
> breakpoints etc; this works for all our TCG CPUs, but will break if
> we ever add an AArch64-only CPU.  We also have an assert() that the
> AArch32 and AArch64 registers match, which currently works only by
> luck for KVM because we don't populate either of these ID registers
> from the KVM vCPU and so they are both zero.
> Clean this up so we have functions for finding the number
> of breakpoints, watchpoints and context comparators which look
> in the appropriate ID register.
> This allows us to drop the "check that AArch64 and AArch32 agree
> on the number of breakpoints etc" asserts:
>  * we no longer look at the AArch32 versions unless that's the
>    right place to be looking
>  * it's valid to have a CPU (eg AArch64-only) where they don't match
>  * we shouldn't have been asserting the validity of ID registers
>    in a codepath used with KVM anyway
> Signed-off-by: Peter Maydell <address@hidden>
> ---
>  target/arm/cpu.h          |  7 +++++++
>  target/arm/internals.h    | 42 +++++++++++++++++++++++++++++++++++++++
>  target/arm/debug_helper.c |  6 +++---
>  target/arm/helper.c       | 21 +++++---------------
>  4 files changed, 57 insertions(+), 19 deletions(-)

Reviewed-by: Richard Henderson <address@hidden>


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