Add SLB switching code for entry/exit

This is the really low level of guest entry/exit code.

Book3s_64 has an SLB, which stores all ESID -> VSID mappings we're
currently aware of.

The segments in the guest differ from the ones on the host, so we need
to switch the SLB to tell the MMU that we're in a new context.

So we store a shadow of the guest's SLB in the PACA, switch to that on
entry and only restore bolted entries on exit, leaving the rest to the
Linux SLB fault handler.

That way we get a really clean way of switching the SLB.
Signed-off-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/kvm/book3s_64_slb.S

+/*
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License, version 2, as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+ *
+ * Copyright SUSE Linux Products GmbH 2009
+ *
+ * Authors: Alexander Graf <agraf@suse.de>
+ */
+
+#define SHADOW_SLB_ESID(num)	(SLBSHADOW_SAVEAREA + (num * 0x10))
+#define SHADOW_SLB_VSID(num)	(SLBSHADOW_SAVEAREA + (num * 0x10) + 0x8)
+#define UNBOLT_SLB_ENTRY(num) \
+	ld	r9, SHADOW_SLB_ESID(num)(r12); \
+	/* Invalid? Skip. */; \
+	rldicl. r0, r9, 37, 63; \
+	beq	slb_entry_skip_ ## num; \
+	xoris	r9, r9, SLB_ESID_V@h; \
+	std	r9, SHADOW_SLB_ESID(num)(r12); \
+  slb_entry_skip_ ## num:
+
+#define REBOLT_SLB_ENTRY(num) \
+	ld	r10, SHADOW_SLB_ESID(num)(r11); \
+	cmpdi	r10, 0; \
+	beq	slb_exit_skip_1; \
+	oris	r10, r10, SLB_ESID_V@h; \
+	ld	r9, SHADOW_SLB_VSID(num)(r11); \
+	slbmte	r9, r10; \
+	std	r10, SHADOW_SLB_ESID(num)(r11); \
+slb_exit_skip_ ## num:
+
+/******************************************************************************
+ *                                                                            *
+ *                               Entry code                                   *
+ *                                                                            *
+ *****************************************************************************/
+
+.global kvmppc_handler_trampoline_enter
+kvmppc_handler_trampoline_enter:
+
+	/* Required state:
+	 *
+	 * MSR = ~IR|DR
+	 * R13 = PACA
+	 * R9 = guest IP
+	 * R10 = guest MSR
+	 * R11 = free
+	 * R12 = free
+	 * PACA[PACA_EXMC + EX_R9] = guest R9
+	 * PACA[PACA_EXMC + EX_R10] = guest R10
+	 * PACA[PACA_EXMC + EX_R11] = guest R11
+	 * PACA[PACA_EXMC + EX_R12] = guest R12
+	 * PACA[PACA_EXMC + EX_R13] = guest R13
+	 * PACA[PACA_EXMC + EX_CCR] = guest CR
+	 * PACA[PACA_EXMC + EX_R3] = guest XER
+	 */
+
+	mtsrr0	r9
+	mtsrr1	r10
+
+	mtspr	SPRN_SPRG_SCRATCH0, r0
+
+	/* Remove LPAR shadow entries */
+
+#if SLB_NUM_BOLTED == 3
+
+	ld	r12, PACA_SLBSHADOWPTR(r13)
+
+	/* Save off the first entry so we can slbie it later */
+	ld	r10, SHADOW_SLB_ESID(0)(r12)
+	ld	r11, SHADOW_SLB_VSID(0)(r12)
+
+	/* Remove bolted entries */
+	UNBOLT_SLB_ENTRY(0)
+	UNBOLT_SLB_ENTRY(1)
+	UNBOLT_SLB_ENTRY(2)
+	
+#else
+#error unknown number of bolted entries
+#endif
+
+	/* Flush SLB */
+
+	slbia
+
+	/* r0 = esid & ESID_MASK */
+	rldicr  r10, r10, 0, 35
+	/* r0 |= CLASS_BIT(VSID) */
+	rldic   r12, r11, 56 - 36, 36
+	or      r10, r10, r12
+	slbie	r10
+
+	isync
+
+	/* Fill SLB with our shadow */
+
+	lbz	r12, PACA_KVM_SLB_MAX(r13)
+	mulli	r12, r12, 16
+	addi	r12, r12, PACA_KVM_SLB
+	add	r12, r12, r13
+
+	/* for (r11 = kvm_slb; r11 < kvm_slb + kvm_slb_size; r11+=slb_entry) */
+	li	r11, PACA_KVM_SLB
+	add	r11, r11, r13
+
+slb_loop_enter:
+
+	ld	r10, 0(r11)
+
+	rldicl. r0, r10, 37, 63
+	beq	slb_loop_enter_skip
+
+	ld	r9, 8(r11)
+	slbmte	r9, r10
+
+slb_loop_enter_skip:
+	addi	r11, r11, 16
+	cmpd	cr0, r11, r12
+	blt	slb_loop_enter
+
+slb_do_enter:
+
+	/* Enter guest */
+
+	mfspr	r0, SPRN_SPRG_SCRATCH0
+
+	ld	r9, (PACA_EXMC+EX_R9)(r13)
+	ld	r10, (PACA_EXMC+EX_R10)(r13)
+	ld	r12, (PACA_EXMC+EX_R12)(r13)
+
+	lwz	r11, (PACA_EXMC+EX_CCR)(r13)
+	mtcr	r11
+
+	ld	r11, (PACA_EXMC+EX_R3)(r13)
+	mtxer	r11
+
+	ld	r11, (PACA_EXMC+EX_R11)(r13)
+	ld	r13, (PACA_EXMC+EX_R13)(r13)
+
+	RFI
+kvmppc_handler_trampoline_enter_end:
+
+
+
+/******************************************************************************
+ *                                                                            *
+ *                               Exit code                                    *
+ *                                                                            *
+ *****************************************************************************/
+
+.global kvmppc_handler_trampoline_exit
+kvmppc_handler_trampoline_exit:
+
+	/* Register usage at this point:
+	 *
+	 * SPRG_SCRATCH0 = guest R13
+	 * R01           = host R1
+	 * R02           = host R2
+	 * R10           = guest PC
+	 * R11           = guest MSR
+	 * R12           = exit handler id
+	 * R13           = PACA
+	 * PACA.exmc.CCR  = guest CR
+	 * PACA.exmc.R9  = guest R1
+	 * PACA.exmc.R10 = guest R10
+	 * PACA.exmc.R11 = guest R11
+	 * PACA.exmc.R12 = guest R12
+	 * PACA.exmc.R13 = guest R2
+	 *
+	 */
+
+	/* Save registers */
+
+	std	r0, (PACA_EXMC+EX_SRR0)(r13)
+	std	r9, (PACA_EXMC+EX_R3)(r13)
+	std	r10, (PACA_EXMC+EX_LR)(r13)
+	std	r11, (PACA_EXMC+EX_DAR)(r13)
+
+	/*
+	 * In order for us to easily get the last instruction,
+	 * we got the #vmexit at, we exploit the fact that the
+	 * virtual layout is still the same here, so we can just
+	 * ld from the guest's PC address
+	 */
+
+	/* We only load the last instruction when it's safe */
+	cmpwi	r12, BOOK3S_INTERRUPT_DATA_STORAGE
+	beq	ld_last_inst
+	cmpwi	r12, BOOK3S_INTERRUPT_PROGRAM
+	beq	ld_last_inst
+
+	b	no_ld_last_inst
+
+ld_last_inst:
+	/* Save off the guest instruction we're at */
+	/*    1) enable paging for data */
+	mfmsr	r9
+	ori	r11, r9, MSR_DR			/* Enable paging for data */
+	mtmsr	r11
+	/*    2) fetch the instruction */
+	lwz	r0, 0(r10)
+	/*    3) disable paging again */
+	mtmsr	r9
+
+no_ld_last_inst:
+
+	/* Restore bolted entries from the shadow and fix it along the way */
+
+	/* We don't store anything in entry 0, so we don't need to take care of it */
+	slbia
+	isync
+
+#if SLB_NUM_BOLTED == 3
+
+	ld	r11, PACA_SLBSHADOWPTR(r13)
+
+	REBOLT_SLB_ENTRY(0)
+	REBOLT_SLB_ENTRY(1)
+	REBOLT_SLB_ENTRY(2)
+	
+#else
+#error unknown number of bolted entries
+#endif
+
+slb_do_exit:
+
+	/* Restore registers */
+
+	ld	r11, (PACA_EXMC+EX_DAR)(r13)
+	ld	r10, (PACA_EXMC+EX_LR)(r13)
+	ld	r9, (PACA_EXMC+EX_R3)(r13)
+
+	/* Save last inst */
+	stw	r0, (PACA_EXMC+EX_LR)(r13)
+
+	/* Save DAR and DSISR before going to paged mode */
+	mfdar	r0
+	std	r0, (PACA_EXMC+EX_DAR)(r13)
+	mfdsisr	r0
+	stw	r0, (PACA_EXMC+EX_DSISR)(r13)
+
+	/* RFI into the highmem handler */
+	mfmsr	r0
+	ori	r0, r0, MSR_IR|MSR_DR|MSR_RI	/* Enable paging */
+	mtsrr1	r0
+	ld	r0, PACASAVEDMSR(r13)		/* Highmem handler address */
+	mtsrr0	r0
+
+	mfspr	r0, SPRN_SPRG_SCRATCH0
+
+	RFI
+kvmppc_handler_trampoline_exit_end:
+