[Qemu-ppc] [RFC PATCH 12/17] PowerPC: booke64: Add DO_KVM kernel hooks

[Alexander Graf]

On 07.07.2012, at 10:39, Caraman Mihai Claudiu-B02008 wrote:

>> ________________________________________
>> From: Alexander Graf [agraf at suse.de]
>> Sent: Saturday, July 07, 2012 2:11 AM
>> To: Caraman Mihai Claudiu-B02008
>> Cc: Benjamin Herrenschmidt; <kvm-ppc at vger.kernel.org>; KVM list; linuxppc-dev; qemu-ppc at nongnu.org List
>> Subject: Re: [Qemu-ppc] [RFC PATCH 12/17] PowerPC: booke64: Add DO_KVM kernel hooks
>> 
>> On 07.07.2012, at 00:33, Caraman Mihai Claudiu-B02008 wrote:
>> 
>>>> -----Original Message-----
>>>> From: Benjamin Herrenschmidt [mailto:benh at kernel.crashing.org]
>>>> Sent: Thursday, July 05, 2012 1:26 AM
>>>> To: Alexander Graf
>>>> Cc: Caraman Mihai Claudiu-B02008; <kvm-ppc at vger.kernel.org>; KVM list;
>>>> linuxppc-dev; qemu-ppc at nongnu.org List
>>>> Subject: Re: [Qemu-ppc] [RFC PATCH 12/17] PowerPC: booke64: Add DO_KVM
>>>> kernel hooks
>>>> 
>>>> You can't but in any case I don't see the point of the conditional here,
>>>> we'll eventually have to load srr1 no ? We can move the load up to here
>>>> in all cases or can't we ?
>>> 
>>> I like the idea, but there is a problem with addition macros which may clobber
>>> r11 and PROLOG_ADDITION_MASKABLE_GEN is such a case.
>> 
>> Mike -v please :)
> 
> Ben suggested something like this:
> 	
> #define EXCEPTION_PROLOG(n, type, addition) \
> 	mtspr SPRN_SPRG_##type##_SCRATCH,r13; /* get spare registers */ \
> 	mfspr r13,SPRN_SPRG_PACA; /* get PACA */ \
> 	std r10,PACA_EX##type+EX_R10(r13); \
> 	std r11,PACA_EX##type+EX_R11(r13); \
> 	mfcr r10; /* save CR */ \	
> +	mfspr r11,SPRN_##type##_SRR1;/* what are we coming from */ \
> 	DO_KVM	intnum,srr1; \
> 	addition; /* additional code for that exc. */ \
> 	std r1,PACA_EX##type+EX_R1(r13); /* save old r1 in the PACA */ \
> 	stw r10,PACA_EX##type+EX_CR(r13); /* save old CR in the PACA */ \
> -	mfspr r11,SPRN_##type##_SRR1;/* what are we coming from */ \
> 	type##_SET_KSTACK; /* get special stack if necessary */\
> 	andi. r10,r11,MSR_PR; /* save stack pointer */ \
> 
> But one of the addition looks like this:
> 	
> #define PROLOG_ADDITION_MASKABLE_GEN(n) \
> 	lbz r11,PACASOFTIRQEN(r13); /* are irqs soft-disabled ? */ \
> 	cmpwi cr0,r11,0; /* yes -> go out of line */ \
> 	beq masked_interrupt_book3e_##n	
> 
> So for maskable gen we end up with:
> 
> #define EXCEPTION_PROLOG(n, type, addition) \
> 	mtspr SPRN_SPRG_##type##_SCRATCH,r13; /* get spare registers */ \
> 	mfspr r13,SPRN_SPRG_PACA; /* get PACA */ \
> 	std r10,PACA_EX##type+EX_R10(r13); \
> 	std r11,PACA_EX##type+EX_R11(r13); \
> 	mfcr r10; /* save CR */ \
> 	mfspr r11,SPRN_##type##_SRR1;/* what are we coming from */ \
> 	DO_KVM	intnum,srr1; \
> 	lbz r11,PACASOFTIRQEN(r13); /* are irqs soft-disabled ? */ \
> 	cmpwi cr0,r11,0; /* yes -> go out of line */ \
> 	beq masked_interrupt_book3e_##n	\
> 	std r1,PACA_EX##type+EX_R1(r13); /* save old r1 in the PACA */ \
> 	stw r10,PACA_EX##type+EX_CR(r13); /* save old CR in the PACA */ \
> 	type##_SET_KSTACK; /* get special stack if necessary */\
> 	andi. r10,r11,MSR_PR; /* save stack pointer */ \
> 	
> This affects the last asm line, we load srr1 into r11 but clobber it in-between.
> We need a spare register for maskable gen addition. I think we can free r10 sooner
> and used it in addition like this:

Ah, makes sense, yes.

> 
> #define EXCEPTION_PROLOG(n, type, addition) \
> 	mtspr SPRN_SPRG_##type##_SCRATCH,r13; /* get spare registers */ \
> 	mfspr r13,SPRN_SPRG_PACA; /* get PACA */ \		
> 	std r10,PACA_EX##type+EX_R10(r13); \
> 	std r11,PACA_EX##type+EX_R11(r13); \

Or just free up another register early on, like here.


Alex

> +	mfspr r11,SPRN_##type##_SRR1;/* what are we coming from */ \
> 	mfcr r10; /* save CR */ \
> + 	stw r10,PACA_EX##type+EX_CR(r13); /* save old CR in the PACA */ \
> 	DO_KVM	intnum,srr1; \
> -	lbz r11,PACASOFTIRQEN(r13); /* are irqs soft-disabled ? */ \
> -	cmpwi cr0,r11,0; /* yes -> go out of line */ \
> +	lbz r10,PACASOFTIRQEN(r13); /* are irqs soft-disabled ? */ \
> +	cmpwi cr0,r10,0; /* yes -> go out of line */ \
> 	beq masked_interrupt_book3e_##n	\
> 	std r1,PACA_EX##type+EX_R1(r13); /* save old r1 in the PACA */ \
> - 	stw r10,PACA_EX##type+EX_CR(r13); /* save old CR in the PACA */ \
> -	mfspr r11,SPRN_##type##_SRR1;/* what are we coming from */ \
> 	type##_SET_KSTACK; /* get special stack if necessary */\
> 	andi. r10,r11,MSR_PR; /* save stack pointer */ \
> 	
> -Mike
> --
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