KVM: PPC: book3s_pr: Simplify transitions between virtual and real mode

This simplifies the way that the book3s_pr makes the transition to
real mode when entering the guest.  We now call kvmppc_entry_trampoline
(renamed from kvmppc_rmcall) in the base kernel using a normal function
call instead of doing an indirect call through a pointer in the vcpu.
If kvm is a module, the module loader takes care of generating a
trampoline as it does for other calls to functions outside the module.

kvmppc_entry_trampoline then disables interrupts and jumps to
kvmppc_handler_trampoline_enter in real mode using an rfi[d].
That then uses the link register as the address to return to
(potentially in module space) when the guest exits.

This also simplifies the way that we call the Linux interrupt handler
when we exit the guest due to an external, decrementer or performance
monitor interrupt.  Instead of turning on the MMU, then deciding that
we need to call the Linux handler and turning the MMU back off again,
we now go straight to the handler at the point where we would turn the
MMU on.  The handler will then return to the virtual-mode code
(potentially in the module).

Along the way, this moves the setting and clearing of the HID5 DCBZ32
bit into real-mode interrupts-off code, and also makes sure that
we clear the MSR[RI] bit before loading values into SRR0/1.

The net result is that we no longer need any code addresses to be
stored in vcpu->arch.

Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Alexander Graf <agraf@suse.de>

1 files changed, 5 insertions, 124 deletions

diff --git a/arch/powerpc/kvm/book3s_interrupts.S b/arch/powerpc/kvm/book3s_interrupts.S
index c54b0e3..0a8515a 100644
--- a/arch/powerpc/kvm/book3s_interrupts.S
+++ b/arch/powerpc/kvm/book3s_interrupts.S
@@ -29,27 +29,11 @@
 #define ULONG_SIZE 		8
 #define FUNC(name) 		GLUE(.,name)
 
-#define GET_SHADOW_VCPU_R13
-
-#define DISABLE_INTERRUPTS	\
-	mfmsr   r0;		\
-	rldicl  r0,r0,48,1;	\
-	rotldi  r0,r0,16;	\
-	mtmsrd  r0,1;		\
-
 #elif defined(CONFIG_PPC_BOOK3S_32)
 
 #define ULONG_SIZE              4
 #define FUNC(name)		name
 
-#define GET_SHADOW_VCPU_R13	\
-	lwz	r13, (THREAD + THREAD_KVM_SVCPU)(r2)
-
-#define DISABLE_INTERRUPTS	\
-	mfmsr   r0;		\
-	rlwinm  r0,r0,0,17,15;	\
-	mtmsr   r0;		\
-
 #endif /* CONFIG_PPC_BOOK3S_XX */
 
 
@@ -108,44 +92,17 @@ kvm_start_entry:
 
 kvm_start_lightweight:
 
-	GET_SHADOW_VCPU_R13
-	PPC_LL	r3, VCPU_HIGHMEM_HANDLER(r4)
-	PPC_STL	r3, HSTATE_VMHANDLER(r13)
-
-	PPC_LL	r10, VCPU_SHADOW_MSR(r4)	/* r10 = vcpu->arch.shadow_msr */
-
-	DISABLE_INTERRUPTS
-
 #ifdef CONFIG_PPC_BOOK3S_64
-	/* Some guests may need to have dcbz set to 32 byte length.
-	 *
-	 * Usually we ensure that by patching the guest's instructions
-	 * to trap on dcbz and emulate it in the hypervisor.
-	 *
-	 * If we can, we should tell the CPU to use 32 byte dcbz though,
-	 * because that's a lot faster.
-	 */
-
 	PPC_LL	r3, VCPU_HFLAGS(r4)
-	rldicl.	r3, r3, 0, 63		/* CR = ((r3 & 1) == 0) */
-	beq	no_dcbz32_on
-
-	mfspr   r3,SPRN_HID5
-	ori     r3, r3, 0x80		/* XXX HID5_dcbz32 = 0x80 */
-	mtspr   SPRN_HID5,r3
-
-no_dcbz32_on:
-
+	rldicl	r3, r3, 0, 63		/* r3 &= 1 */
+	stb	r3, HSTATE_RESTORE_HID5(r13)
 #endif /* CONFIG_PPC_BOOK3S_64 */
 
-	PPC_LL	r6, VCPU_RMCALL(r4)
-	mtctr	r6
-
-	PPC_LL	r3, VCPU_TRAMPOLINE_ENTER(r4)
-	LOAD_REG_IMMEDIATE(r4, MSR_KERNEL & ~(MSR_IR | MSR_DR))
+	PPC_LL	r4, VCPU_SHADOW_MSR(r4)	/* get shadow_msr */
 
 	/* Jump to segment patching handler and into our guest */
-	bctr
+	bl	FUNC(kvmppc_entry_trampoline)
+	nop
 
 /*
  * This is the handler in module memory. It gets jumped at from the
@@ -170,21 +127,6 @@ kvmppc_handler_highmem:
 	/* R7 = vcpu */
 	PPC_LL	r7, GPR4(r1)
 
-#ifdef CONFIG_PPC_BOOK3S_64
-
-	PPC_LL	r5, VCPU_HFLAGS(r7)
-	rldicl.	r5, r5, 0, 63		/* CR = ((r5 & 1) == 0) */
-	beq	no_dcbz32_off
-
-	li	r4, 0
-	mfspr   r5,SPRN_HID5
-	rldimi  r5,r4,6,56
-	mtspr   SPRN_HID5,r5
-
-no_dcbz32_off:
-
-#endif /* CONFIG_PPC_BOOK3S_64 */
-
 	PPC_STL	r14, VCPU_GPR(r14)(r7)
 	PPC_STL	r15, VCPU_GPR(r15)(r7)
 	PPC_STL	r16, VCPU_GPR(r16)(r7)
@@ -204,67 +146,6 @@ no_dcbz32_off:
 	PPC_STL	r30, VCPU_GPR(r30)(r7)
 	PPC_STL	r31, VCPU_GPR(r31)(r7)
 
-	/* Restore host msr -> SRR1 */
-	PPC_LL	r6, VCPU_HOST_MSR(r7)
-
-	/*
-	 * For some interrupts, we need to call the real Linux
-	 * handler, so it can do work for us. This has to happen
-	 * as if the interrupt arrived from the kernel though,
-	 * so let's fake it here where most state is restored.
-	 *
-	 * Call Linux for hardware interrupts/decrementer
-	 * r3 = address of interrupt handler (exit reason)
-	 */
-
-	cmpwi	r12, BOOK3S_INTERRUPT_EXTERNAL
-	beq	call_linux_handler
-	cmpwi	r12, BOOK3S_INTERRUPT_DECREMENTER
-	beq	call_linux_handler
-	cmpwi	r12, BOOK3S_INTERRUPT_PERFMON
-	beq	call_linux_handler
-
-	/* Back to EE=1 */
-	mtmsr	r6
-	sync
-	b	kvm_return_point
-
-call_linux_handler:
-
-	/*
-	 * If we land here we need to jump back to the handler we
-	 * came from.
-	 *
-	 * We have a page that we can access from real mode, so let's
-	 * jump back to that and use it as a trampoline to get back into the
-	 * interrupt handler!
-	 *
-	 * R3 still contains the exit code,
-	 * R5 VCPU_HOST_RETIP and
-	 * R6 VCPU_HOST_MSR
-	 */
-
-	/* Restore host IP -> SRR0 */
-	PPC_LL	r5, VCPU_HOST_RETIP(r7)
-
-	/* XXX Better move to a safe function?
-	 *     What if we get an HTAB flush in between mtsrr0 and mtsrr1? */
-
-	mtlr	r12
-
-	PPC_LL	r4, VCPU_TRAMPOLINE_LOWMEM(r7)
-	mtsrr0	r4
-	LOAD_REG_IMMEDIATE(r3, MSR_KERNEL & ~(MSR_IR | MSR_DR))
-	mtsrr1	r3
-
-	RFI
-
-.global kvm_return_point
-kvm_return_point:
-
-	/* Jump back to lightweight entry if we're supposed to */
-	/* go back into the guest */
-
 	/* Pass the exit number as 3rd argument to kvmppc_handle_exit */
 	mr	r5, r12