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, 92 insertions, 20 deletions

diff --git a/arch/powerpc/kvm/book3s_segment.S b/arch/powerpc/kvm/book3s_segment.S
index 678b6be31693..0676ae249b9f 100644
--- a/arch/powerpc/kvm/book3s_segment.S
+++ b/arch/powerpc/kvm/book3s_segment.S
@@ -23,6 +23,7 @@
 
 #define GET_SHADOW_VCPU(reg)    \
 	mr	reg, r13
+#define MTMSR_EERI(reg)		mtmsrd	(reg),1
 
 #elif defined(CONFIG_PPC_BOOK3S_32)
 
@@ -30,6 +31,7 @@
 	tophys(reg, r2);       			\
 	lwz     reg, (THREAD + THREAD_KVM_SVCPU)(reg);	\
 	tophys(reg, reg)
+#define MTMSR_EERI(reg)		mtmsr	(reg)
 
 #endif
 
@@ -57,10 +59,12 @@ kvmppc_handler_trampoline_enter:
 	/* Required state:
 	 *
 	 * MSR = ~IR|DR
-	 * R13 = PACA
 	 * R1 = host R1
 	 * R2 = host R2
-	 * R10 = guest MSR
+	 * R4 = guest shadow MSR
+	 * R5 = normal host MSR
+	 * R6 = current host MSR (EE, IR, DR off)
+	 * LR = highmem guest exit code
 	 * all other volatile GPRS = free
 	 * SVCPU[CR] = guest CR
 	 * SVCPU[XER] = guest XER
@@ -71,15 +75,15 @@ kvmppc_handler_trampoline_enter:
 	/* r3 = shadow vcpu */
 	GET_SHADOW_VCPU(r3)
 
+	/* Save guest exit handler address and MSR */
+	mflr	r0
+	PPC_STL	r0, HSTATE_VMHANDLER(r3)
+	PPC_STL	r5, HSTATE_HOST_MSR(r3)
+
 	/* Save R1/R2 in the PACA (64-bit) or shadow_vcpu (32-bit) */
 	PPC_STL	r1, HSTATE_HOST_R1(r3)
 	PPC_STL	r2, HSTATE_HOST_R2(r3)
 
-	/* Move SRR0 and SRR1 into the respective regs */
-	PPC_LL  r9, SVCPU_PC(r3)
-	mtsrr0	r9
-	mtsrr1	r10
-
 	/* Activate guest mode, so faults get handled by KVM */
 	li	r11, KVM_GUEST_MODE_GUEST
 	stb	r11, HSTATE_IN_GUEST(r3)
@@ -87,17 +91,46 @@ kvmppc_handler_trampoline_enter:
 	/* Switch to guest segment. This is subarch specific. */
 	LOAD_GUEST_SEGMENTS
 
+#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.
+	 */
+	lbz	r0, HSTATE_RESTORE_HID5(r3)
+	cmpwi	r0, 0
+	beq	no_dcbz32_on
+
+	mfspr   r0,SPRN_HID5
+	ori     r0, r0, 0x80		/* XXX HID5_dcbz32 = 0x80 */
+	mtspr   SPRN_HID5,r0
+no_dcbz32_on:
+
+#endif /* CONFIG_PPC_BOOK3S_64 */
+
 	/* Enter guest */
 
-	PPC_LL	r4, SVCPU_CTR(r3)
-	PPC_LL	r5, SVCPU_LR(r3)
-	lwz	r6, SVCPU_CR(r3)
-	lwz	r7, SVCPU_XER(r3)
+	PPC_LL	r8, SVCPU_CTR(r3)
+	PPC_LL	r9, SVCPU_LR(r3)
+	lwz	r10, SVCPU_CR(r3)
+	lwz	r11, SVCPU_XER(r3)
+
+	mtctr	r8
+	mtlr	r9
+	mtcr	r10
+	mtxer	r11
 
-	mtctr	r4
-	mtlr	r5
-	mtcr	r6
-	mtxer	r7
+	/* Move SRR0 and SRR1 into the respective regs */
+	PPC_LL  r9, SVCPU_PC(r3)
+	/* First clear RI in our current MSR value */
+	li	r0, MSR_RI
+	andc	r6, r6, r0
+	MTMSR_EERI(r6)
+	mtsrr0	r9
+	mtsrr1	r4
 
 	PPC_LL	r0, SVCPU_R0(r3)
 	PPC_LL	r1, SVCPU_R1(r3)
@@ -259,6 +292,43 @@ no_ld_last_inst:
 	/* Switch back to host MMU */
 	LOAD_HOST_SEGMENTS
 
+#ifdef CONFIG_PPC_BOOK3S_64
+
+	lbz	r5, HSTATE_RESTORE_HID5(r13)
+	cmpwi	r5, 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 */
+
+	/*
+	 * 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.
+	 *
+	 * Having set up SRR0/1 with the address where we want
+	 * to continue with relocation on (potentially in module
+	 * space), we either just go straight there with rfi[d],
+	 * or we jump to an interrupt handler with bctr if there
+	 * is an interrupt to be handled first.  In the latter
+	 * case, the rfi[d] at the end of the interrupt handler
+	 * will get us back to where we want to continue.
+	 */
+
+	cmpwi	r12, BOOK3S_INTERRUPT_EXTERNAL
+	beq	1f
+	cmpwi	r12, BOOK3S_INTERRUPT_DECREMENTER
+	beq	1f
+	cmpwi	r12, BOOK3S_INTERRUPT_PERFMON
+1:	mtctr	r12
+
 	/* Register usage at this point:
 	 *
 	 * R1       = host R1
@@ -269,13 +339,15 @@ no_ld_last_inst:
 	 *
 	 */
 
-	/* RFI into the highmem handler */
-	mfmsr	r7
-	ori	r7, r7, MSR_IR|MSR_DR|MSR_RI|MSR_ME	/* Enable paging */
-	mtsrr1	r7
-	/* Load highmem handler address */
+	PPC_LL	r6, HSTATE_HOST_MSR(r13)
 	PPC_LL	r8, HSTATE_VMHANDLER(r13)
+
+	/* Restore host msr -> SRR1 */
+	mtsrr1	r6
+	/* Load highmem handler address */
 	mtsrr0	r8
 
+	/* RFI into the highmem handler, or jump to interrupt handler */
+	beqctr
 	RFI
 kvmppc_handler_trampoline_exit_end: