KVM: PPC: Implement MMIO emulation support for Book3S HV guests

This provides the low-level support for MMIO emulation in Book3S HV
guests.  When the guest tries to map a page which is not covered by
any memslot, that page is taken to be an MMIO emulation page.  Instead
of inserting a valid HPTE, we insert an HPTE that has the valid bit
clear but another hypervisor software-use bit set, which we call
HPTE_V_ABSENT, to indicate that this is an absent page.  An
absent page is treated much like a valid page as far as guest hcalls
(H_ENTER, H_REMOVE, H_READ etc.) are concerned, except of course that
an absent HPTE doesn't need to be invalidated with tlbie since it
was never valid as far as the hardware is concerned.

When the guest accesses a page for which there is an absent HPTE, it
will take a hypervisor data storage interrupt (HDSI) since we now set
the VPM1 bit in the LPCR.  Our HDSI handler for HPTE-not-present faults
looks up the hash table and if it finds an absent HPTE mapping the
requested virtual address, will switch to kernel mode and handle the
fault in kvmppc_book3s_hv_page_fault(), which at present just calls
kvmppc_hv_emulate_mmio() to set up the MMIO emulation.

This is based on an earlier patch by Benjamin Herrenschmidt, but since
heavily reworked.

Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Avi Kivity <avi@redhat.com>

1 files changed, 105 insertions, 22 deletions

diff --git a/arch/powerpc/kvm/book3s_hv_rmhandlers.S b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
index 5c8b26183f5..d07b64d5f37 100644
--- a/arch/powerpc/kvm/book3s_hv_rmhandlers.S
+++ b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
@@ -601,6 +601,28 @@ kvmppc_interrupt:
 
 	stw	r12,VCPU_TRAP(r9)
 
+	/* Save HEIR (HV emulation assist reg) in last_inst
+	   if this is an HEI (HV emulation interrupt, e40) */
+	li	r3,KVM_INST_FETCH_FAILED
+BEGIN_FTR_SECTION
+	cmpwi	r12,BOOK3S_INTERRUPT_H_EMUL_ASSIST
+	bne	11f
+	mfspr	r3,SPRN_HEIR
+END_FTR_SECTION_IFSET(CPU_FTR_ARCH_206)
+11:	stw	r3,VCPU_LAST_INST(r9)
+
+	/* these are volatile across C function calls */
+	mfctr	r3
+	mfxer	r4
+	std	r3, VCPU_CTR(r9)
+	stw	r4, VCPU_XER(r9)
+
+BEGIN_FTR_SECTION
+	/* If this is a page table miss then see if it's theirs or ours */
+	cmpwi	r12, BOOK3S_INTERRUPT_H_DATA_STORAGE
+	beq	kvmppc_hdsi
+END_FTR_SECTION_IFSET(CPU_FTR_ARCH_206)
+
 	/* See if this is a leftover HDEC interrupt */
 	cmpwi	r12,BOOK3S_INTERRUPT_HV_DECREMENTER
 	bne	2f
@@ -608,7 +630,7 @@ kvmppc_interrupt:
 	cmpwi	r3,0
 	bge	ignore_hdec
 2:
-	/* See if this is something we can handle in real mode */
+	/* See if this is an hcall we can handle in real mode */
 	cmpwi	r12,BOOK3S_INTERRUPT_SYSCALL
 	beq	hcall_try_real_mode
 
@@ -624,6 +646,7 @@ BEGIN_FTR_SECTION
 1:
 END_FTR_SECTION_IFSET(CPU_FTR_ARCH_206)
 
+nohpte_cont:
 hcall_real_cont:		/* r9 = vcpu, r12 = trap, r13 = paca */
 	/* Save DEC */
 	mfspr	r5,SPRN_DEC
@@ -632,36 +655,21 @@ hcall_real_cont:		/* r9 = vcpu, r12 = trap, r13 = paca */
 	add	r5,r5,r6
 	std	r5,VCPU_DEC_EXPIRES(r9)
 
-	/* Save HEIR (HV emulation assist reg) in last_inst
-	   if this is an HEI (HV emulation interrupt, e40) */
-	li	r3,-1
-BEGIN_FTR_SECTION
-	cmpwi	r12,BOOK3S_INTERRUPT_H_EMUL_ASSIST
-	bne	11f
-	mfspr	r3,SPRN_HEIR
-END_FTR_SECTION_IFSET(CPU_FTR_ARCH_206)
-11:	stw	r3,VCPU_LAST_INST(r9)
-
 	/* Save more register state  */
-	mfxer	r5
 	mfdar	r6
 	mfdsisr	r7
-	mfctr	r8
-
-	stw	r5, VCPU_XER(r9)
 	std	r6, VCPU_DAR(r9)
 	stw	r7, VCPU_DSISR(r9)
-	std	r8, VCPU_CTR(r9)
-	/* grab HDAR & HDSISR if HV data storage interrupt (HDSI) */
 BEGIN_FTR_SECTION
+	/* don't overwrite fault_dar/fault_dsisr if HDSI */
 	cmpwi	r12,BOOK3S_INTERRUPT_H_DATA_STORAGE
 	beq	6f
 END_FTR_SECTION_IFSET(CPU_FTR_ARCH_206)
-7:	std	r6, VCPU_FAULT_DAR(r9)
+	std	r6, VCPU_FAULT_DAR(r9)
 	stw	r7, VCPU_FAULT_DSISR(r9)
 
 	/* Save guest CTRL register, set runlatch to 1 */
-	mfspr	r6,SPRN_CTRLF
+6:	mfspr	r6,SPRN_CTRLF
 	stw	r6,VCPU_CTRL(r9)
 	andi.	r0,r6,1
 	bne	4f
@@ -1094,9 +1102,84 @@ END_FTR_SECTION_IFSET(CPU_FTR_ARCH_201)
 	mtspr	SPRN_HSRR1, r7
 	ba	0x500
 
-6:	mfspr	r6,SPRN_HDAR
-	mfspr	r7,SPRN_HDSISR
-	b	7b
+/*
+ * Check whether an HDSI is an HPTE not found fault or something else.
+ * If it is an HPTE not found fault that is due to the guest accessing
+ * a page that they have mapped but which we have paged out, then
+ * we continue on with the guest exit path.  In all other cases,
+ * reflect the HDSI to the guest as a DSI.
+ */
+kvmppc_hdsi:
+	mfspr	r4, SPRN_HDAR
+	mfspr	r6, SPRN_HDSISR
+	/* HPTE not found fault? */
+	andis.	r0, r6, DSISR_NOHPTE@h
+	beq	1f			/* if not, send it to the guest */
+	andi.	r0, r11, MSR_DR		/* data relocation enabled? */
+	beq	3f
+	clrrdi	r0, r4, 28
+	PPC_SLBFEE_DOT(r5, r0)		/* if so, look up SLB */
+	bne	1f			/* if no SLB entry found */
+4:	std	r4, VCPU_FAULT_DAR(r9)
+	stw	r6, VCPU_FAULT_DSISR(r9)
+
+	/* Search the hash table. */
+	mr	r3, r9			/* vcpu pointer */
+	bl	.kvmppc_hpte_hv_fault
+	ld	r9, HSTATE_KVM_VCPU(r13)
+	ld	r10, VCPU_PC(r9)
+	ld	r11, VCPU_MSR(r9)
+	li	r12, BOOK3S_INTERRUPT_H_DATA_STORAGE
+	cmpdi	r3, 0			/* retry the instruction */
+	beq	6f
+	cmpdi	r3, -1			/* handle in kernel mode */
+	beq	nohpte_cont
+	cmpdi	r3, -2			/* MMIO emulation; need instr word */
+	beq	2f
+
+	/* Synthesize a DSI for the guest */
+	ld	r4, VCPU_FAULT_DAR(r9)
+	mr	r6, r3
+1:	mtspr	SPRN_DAR, r4
+	mtspr	SPRN_DSISR, r6
+	mtspr	SPRN_SRR0, r10
+	mtspr	SPRN_SRR1, r11
+	li	r10, BOOK3S_INTERRUPT_DATA_STORAGE
+	li	r11, (MSR_ME << 1) | 1	/* synthesize MSR_SF | MSR_ME */
+	rotldi	r11, r11, 63
+6:	ld	r7, VCPU_CTR(r9)
+	lwz	r8, VCPU_XER(r9)
+	mtctr	r7
+	mtxer	r8
+	mr	r4, r9
+	b	fast_guest_return
+
+3:	ld	r5, VCPU_KVM(r9)	/* not relocated, use VRMA */
+	ld	r5, KVM_VRMA_SLB_V(r5)
+	b	4b
+
+	/* If this is for emulated MMIO, load the instruction word */
+2:	li	r8, KVM_INST_FETCH_FAILED	/* In case lwz faults */
+
+	/* Set guest mode to 'jump over instruction' so if lwz faults
+	 * we'll just continue at the next IP. */
+	li	r0, KVM_GUEST_MODE_SKIP
+	stb	r0, HSTATE_IN_GUEST(r13)
+
+	/* Do the access with MSR:DR enabled */
+	mfmsr	r3
+	ori	r4, r3, MSR_DR		/* Enable paging for data */
+	mtmsrd	r4
+	lwz	r8, 0(r10)
+	mtmsrd	r3
+
+	/* Store the result */
+	stw	r8, VCPU_LAST_INST(r9)
+
+	/* Unset guest mode. */
+	li	r0, KVM_GUEST_MODE_NONE
+	stb	r0, HSTATE_IN_GUEST(r13)
+	b	nohpte_cont
 
 /*
  * Try to handle an hcall in real mode.