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Date:   Sat, 06 Feb 2021 12:30:35 +1000
From:   Nicholas Piggin <npiggin@gmail.com>
Subject: Re: [PATCH] powerpc/8xx: Fix software emulation interrupt
To:     Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Christophe Leroy <christophe.leroy@csgroup.eu>,
        Michael Ellerman <mpe@ellerman.id.au>,
        Paul Mackerras <paulus@samba.org>
Cc:     linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org
References: <ad782af87a222efc79cfb06079b0fd23d4224eaf.1612515180.git.christophe.leroy@csgroup.eu>
In-Reply-To: <ad782af87a222efc79cfb06079b0fd23d4224eaf.1612515180.git.christophe.leroy@csgroup.eu>
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Excerpts from Christophe Leroy's message of February 5, 2021 6:56 pm:
> For unimplemented instructions or unimplemented SPRs, the 8xx triggers
> a "Software Emulation Exception" (0x1000). That interrupt doesn't set
> reason bits in SRR1 as the "Program Check Exception" does.
>=20
> Go through emulation_assist_interrupt() to set REASON_ILLEGAL.
>=20
> Fixes: fbbcc3bb139e ("powerpc/8xx: Remove SoftwareEmulation()")
> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
> ---
> I'm wondering whether it wouldn't be better to set REASON_ILLEGAL
> in the exception prolog and still call program_check_exception.
> And do the same in book3s/64 to avoid the nightmare of an
> INTERRUPT_HANDLER calling another INTERRUPT_HANDLER.

Hmm, I missed this. We just change program_check_exception to
a common function which is called by both.

Thanks,
Nick