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>

1 files changed, 262 insertions, 0 deletions

diff --git a/arch/powerpc/kvm/book3s_64_slb.S b/arch/powerpc/kvm/book3s_64_slb.S
new file mode 100644
index 000000000000..ecd237a03fd0
--- /dev/null
+++ b/arch/powerpc/kvm/book3s_64_slb.S
@@ -0,0 +1,262 @@
+/*
+ * 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:
+