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Subject: Re: [PATCH v3 14/16] powerpc/32: implement fast entry for syscalls on
 BOOKE
To:     Paul Mackerras <paulus@ozlabs.org>
Cc:     Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Michael Ellerman <mpe@ellerman.id.au>,
        Nicholas Piggin <npiggin@gmail.com>,
        linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org
References: <cover.1556627571.git.christophe.leroy@c-s.fr>
 <3e254178a157e7eaeef48f983880f71f97d1f296.1556627571.git.christophe.leroy@c-s.fr>
 <20190523061427.GA19655@blackberry>
From:   Christophe Leroy <christophe.leroy@c-s.fr>
Message-ID: <4f5fa8af-08c2-e71a-dd43-4c1a64018409@c-s.fr>
Date:   Tue, 4 Jun 2019 18:59:51 +0200
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Paul,

Le 23/05/2019 à 08:14, Paul Mackerras a écrit :
> On Tue, Apr 30, 2019 at 12:39:03PM +0000, Christophe Leroy wrote:
>> This patch implements a fast entry for syscalls.
>>
>> Syscalls don't have to preserve non volatile registers except LR.
>>
>> This patch then implement a fast entry for syscalls, where
>> volatile registers get clobbered.
>>
>> As this entry is dedicated to syscall it always sets MSR_EE
>> and warns in case MSR_EE was previously off
>>
>> It also assumes that the call is always from user, system calls are
>> unexpected from kernel.
> 
> This is now upstream as commit 1a4b739bbb4f.  On the e500mc test
> config that I use, I'm getting this build failure:
> 
> arch/powerpc/kernel/head_fsl_booke.o: In function `SystemCall':
> arch/powerpc/kernel/head_fsl_booke.S:416: undefined reference to `kvmppc_handler_BOOKE_INTERRUPT_SYSCALL_SPRN_SRR1'
> Makefile:1052: recipe for target 'vmlinux' failed

Does my patch (https://patchwork.ozlabs.org/patch/1103909/) fixes the 
issue for you ?

Thanks
Christophe

> 
>> +.macro SYSCALL_ENTRY trapno intno
>> +	mfspr	r10, SPRN_SPRG_THREAD
>> +#ifdef CONFIG_KVM_BOOKE_HV
>> +BEGIN_FTR_SECTION
>> +	mtspr	SPRN_SPRG_WSCRATCH0, r10
>> +	stw	r11, THREAD_NORMSAVE(0)(r10)
>> +	stw	r13, THREAD_NORMSAVE(2)(r10)
>> +	mfcr	r13			/* save CR in r13 for now	   */
>> +	mfspr	r11, SPRN_SRR1
>> +	mtocrf	0x80, r11	/* check MSR[GS] without clobbering reg */
>> +	bf	3, 1975f
>> +	b	kvmppc_handler_BOOKE_INTERRUPT_\intno\()_SPRN_SRR1
> 
> It seems to me that the "_SPRN_SRR1" on the end of this line
> isn't meant to be there...  However, it still fails to link with that
> removed.
> 
> Paul.
>