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

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

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________________________________________
From: Alexander Graf [agraf@suse.de]
Sent: Saturday, July 07, 2012 2:11 AM
To: Caraman Mihai Claudiu-B02008
Cc: Benjamin Herrenschmidt; <redacted>; KVM list; =

linuxppc-dev; qemu-ppc@nongnu.org List

quoted

Subject: Re: [Qemu-ppc] [RFC PATCH 12/17] PowerPC: booke64: Add =

DO_KVM kernel hooks

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=20
On 07.07.2012, at 00:33, Caraman Mihai Claudiu-B02008 wrote:
=20

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-----Original Message-----
From: Benjamin Herrenschmidt [mailto:benh@kernel.crashing.org]
Sent: Thursday, July 05, 2012 1:26 AM
To: Alexander Graf
Cc: Caraman Mihai Claudiu-B02008; <redacted>; KVM =

list;

quoted

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linuxppc-dev; qemu-ppc@nongnu.org List
Subject: Re: [Qemu-ppc] [RFC PATCH 12/17] PowerPC: booke64: Add =

DO_KVM

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kernel hooks
=20
You can't but in any case I don't see the point of the conditional =

here,

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we'll eventually have to load srr1 no ? We can move the load up to =

here

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in all cases or can't we ?

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I like the idea, but there is a problem with addition macros which =

may clobber

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r11 and PROLOG_ADDITION_MASKABLE_GEN is such a case.

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Mike -v please :)

=20
Ben suggested something like this:
=09
#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 */ \=09
+	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 */ \
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But one of the addition looks like this:
=09
#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=09
=20
So for maskable gen we end up with:
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#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 */ \
=09
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.

=20
#define EXCEPTION_PROLOG(n, type, addition) \
	mtspr SPRN_SPRG_##type##_SCRATCH,r13; /* get spare registers */ =

\

	mfspr r13,SPRN_SPRG_PACA; /* get PACA */ \	=09
	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 */ \
=09
-Mike
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