[PATCH 2/6] KVM: PPC: Book3S HV: Do SLB load/unload with guest LPCR value loaded

[Paul Mackerras <paulus@ozlabs.org>]

This moves the code that loads and unloads the guest SLB values so that
it is done while the guest LPCR value is loaded in the LPCR register.
The reason for doing this is that on POWER9, the behaviour of the
slbmte instruction depends on the LPCR[UPRT] bit.  If UPRT is 1, as
it is for a radix host (or guest), the SLB index is truncated to
2 bits.  This means that for a HPT guest on a radix host, the SLB
was not being loaded correctly, causing the guest to crash.

The SLB is now loaded much later in the guest entry path, after the
LPCR is loaded, which for a secondary thread is after it sees that
the primary thread has switched the MMU to the guest.  The loop that
waits for the primary thread has a branch out to the exit code that
is taken if it sees that other threads have commenced exiting the
guest.  Since we have now not loaded the SLB at this point, we make
this path branch to a new label 'guest_bypass' and we move the SLB
unload code to before this label.

Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
---
 arch/powerpc/kvm/book3s_hv_rmhandlers.S | 109 ++++++++++++++++----------------
 1 file changed, 55 insertions(+), 54 deletions(-)

diff --git a/arch/powerpc/kvm/book3s_hv_rmhandlers.S b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
index 76332a3..30ece4c 100644
--- a/arch/powerpc/kvm/book3s_hv_rmhandlers.S
+++ b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
@@ -617,13 +617,6 @@ kvmppc_hv_entry:
 	lbz	r0, KVM_RADIX(r9)
 	cmpwi	cr7, r0, 0
 
-	/* Clear out SLB if hash */
-	bne	cr7, 2f
-	li	r6,0
-	slbmte	r6,r6
-	slbia
-	ptesync
-2:
 	/*
 	 * POWER7/POWER8 host -> guest partition switch code.
 	 * We don't have to lock against concurrent tlbies,
@@ -738,19 +731,6 @@ END_FTR_SECTION_IFSET(CPU_FTR_ARCH_207S)
 10:	cmpdi	r4, 0
 	beq	kvmppc_primary_no_guest
 kvmppc_got_guest:
-
-	/* Load up guest SLB entries (N.B. slb_max will be 0 for radix) */
-	lwz	r5,VCPU_SLB_MAX(r4)
-	cmpwi	r5,0
-	beq	9f
-	mtctr	r5
-	addi	r6,r4,VCPU_SLB
-1:	ld	r8,VCPU_SLB_E(r6)
-	ld	r9,VCPU_SLB_V(r6)
-	slbmte	r9,r8
-	addi	r6,r6,VCPU_SLB_SIZE
-	bdnz	1b
-9:
 	/* Increment yield count if they have a VPA */
 	ld	r3, VCPU_VPA(r4)
 	cmpdi	r3, 0
@@ -1017,6 +997,29 @@ ALT_FTR_SECTION_END_IFCLR(CPU_FTR_ARCH_300)
 	cmpdi	r3, 512		/* 1 microsecond */
 	blt	hdec_soon
 
+	/* For hash guest, clear out and reload the SLB */
+	ld	r6, VCPU_KVM(r4)
+	lbz	r0, KVM_RADIX(r6)
+	cmpwi	r0, 0
+	bne	9f
+	li	r6, 0
+	slbmte	r6, r6
+	slbia
+	ptesync
+
+	/* Load up guest SLB entries (N.B. slb_max will be 0 for radix) */
+	lwz	r5,VCPU_SLB_MAX(r4)
+	cmpwi	r5,0
+	beq	9f
+	mtctr	r5
+	addi	r6,r4,VCPU_SLB
+1:	ld	r8,VCPU_SLB_E(r6)
+	ld	r9,VCPU_SLB_V(r6)
+	slbmte	r9,r8
+	addi	r6,r6,VCPU_SLB_SIZE
+	bdnz	1b
+9:
+
 #ifdef CONFIG_KVM_XICS
 	/* We are entering the guest on that thread, push VCPU to XIVE */
 	ld	r10, HSTATE_XIVE_TIMA_PHYS(r13)
@@ -1193,7 +1196,7 @@ hdec_soon:
 	addi	r3, r4, VCPU_TB_RMEXIT
 	bl	kvmhv_accumulate_time
 #endif
-	b	guest_exit_cont
+	b	guest_bypass
 
 /******************************************************************************
  *                                                                            *
@@ -1481,34 +1484,12 @@ mc_cont:
 1:
 #endif /* CONFIG_KVM_XICS */
 
-	mr 	r3, r12
-	/* Increment exit count, poke other threads to exit */
-	bl	kvmhv_commence_exit
-	nop
-	ld	r9, HSTATE_KVM_VCPU(r13)
-	lwz	r12, VCPU_TRAP(r9)
-
-	/* Stop others sending VCPU interrupts to this physical CPU */
-	li	r0, -1
-	stw	r0, VCPU_CPU(r9)
-	stw	r0, VCPU_THREAD_CPU(r9)
-
-	/* Save guest CTRL register, set runlatch to 1 */
-	mfspr	r6,SPRN_CTRLF
-	stw	r6,VCPU_CTRL(r9)
-	andi.	r0,r6,1
-	bne	4f
-	ori	r6,r6,1
-	mtspr	SPRN_CTRLT,r6
-4:
-	/* Check if we are running hash or radix and store it in cr2 */
+	/* For hash guest, read the guest SLB and save it away */
 	ld	r5, VCPU_KVM(r9)
 	lbz	r0, KVM_RADIX(r5)
-	cmpwi	cr2,r0,0
-
-	/* Read the guest SLB and save it away */
 	li	r5, 0
-	bne	cr2, 3f			/* for radix, save 0 entries */
+	cmpwi	r0, 0
+	bne	3f			/* for radix, save 0 entries */
 	lwz	r0,VCPU_SLB_NR(r9)	/* number of entries in SLB */
 	mtctr	r0
 	li	r6,0
@@ -1524,8 +1505,34 @@ mc_cont:
 	addi	r5,r5,1
 2:	addi	r6,r6,1
 	bdnz	1b
+	/* Finally clear out the SLB */
+	li	r0,0
+	slbmte	r0,r0
+	slbia
+	ptesync
 3:	stw	r5,VCPU_SLB_MAX(r9)
 
+guest_bypass:
+	mr 	r3, r12
+	/* Increment exit count, poke other threads to exit */
+	bl	kvmhv_commence_exit
+	nop
+	ld	r9, HSTATE_KVM_VCPU(r13)
+	lwz	r12, VCPU_TRAP(r9)
+
+	/* Stop others sending VCPU interrupts to this physical CPU */
+	li	r0, -1
+	stw	r0, VCPU_CPU(r9)
+	stw	r0, VCPU_THREAD_CPU(r9)
+
+	/* Save guest CTRL register, set runlatch to 1 */
+	mfspr	r6,SPRN_CTRLF
+	stw	r6,VCPU_CTRL(r9)
+	andi.	r0,r6,1
+	bne	4f
+	ori	r6,r6,1
+	mtspr	SPRN_CTRLT,r6
+4:
 	/*
 	 * Save the guest PURR/SPURR
 	 */
@@ -1803,7 +1810,7 @@ END_FTR_SECTION_IFSET(CPU_FTR_ARCH_300)
 	ld	r5, VCPU_KVM(r9)
 	lbz	r0, KVM_RADIX(r5)
 	cmpwi	cr2, r0, 0
-	beq	cr2, 3f
+	beq	cr2, 4f
 
 	/* Radix: Handle the case where the guest used an illegal PID */
 	LOAD_REG_ADDR(r4, mmu_base_pid)
@@ -1839,15 +1846,9 @@ END_FTR_SECTION_IFSET(CPU_FTR_ARCH_300)
 BEGIN_FTR_SECTION
 	PPC_INVALIDATE_ERAT
 END_FTR_SECTION_IFSET(CPU_FTR_POWER9_DD1)
-	b	4f
+4:
 #endif /* CONFIG_PPC_RADIX_MMU */
 
-	/* Hash: clear out SLB */
-3:	li	r5,0
-	slbmte	r5,r5
-	slbia
-	ptesync
-4:
 	/*
 	 * POWER7/POWER8 guest -> host partition switch code.
 	 * We don't have to lock against tlbies but we do
-- 
2.7.4