KVM: PPC: Add generic segment switching code

This is the code that will later be used instead of book3s_64_slb.S. It
does the last step of guest entry and the first generic steps of guest
exiting, once we have determined the interrupt is a KVM interrupt.

It also reads the last used instruction from the guest virtual address
space if necessary, to speed up that path.

The new thing about this file is that it makes use of generic long load
and store functions and calls a macro to fill in the actual segment
switching code. That still needs to be done differently for book3s_32 and
book3s_64.
Signed-off-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Avi Kivity <avi@redhat.com>

arch/powerpc/kvm/book3s_segment.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 2010
+ *
+ * Authors: Alexander Graf <agraf@suse.de>
+ */
+
+/* Real mode helpers */
+
+#if defined(CONFIG_PPC_BOOK3S_64)
+
+#define GET_SHADOW_VCPU(reg)    \
+	addi    reg, r13, PACA_KVM_SVCPU
+
+#elif defined(CONFIG_PPC_BOOK3S_32)
+
+#define GET_SHADOW_VCPU(reg)    			\
+	tophys(reg, r2);       			\
+	lwz     reg, (THREAD + THREAD_KVM_SVCPU)(reg);	\
+	tophys(reg, reg)
+
+#endif
+
+/* Disable for nested KVM */
+#define USE_QUICK_LAST_INST
+
+
+/* Get helper functions for subarch specific functionality */
+
+#if defined(CONFIG_PPC_BOOK3S_64)
+#include "book3s_64_slb.S"
+#elif defined(CONFIG_PPC_BOOK3S_32)
+#include "book3s_32_sr.S"
+#endif
+
+/******************************************************************************
+ *                                                                            *
+ *                               Entry code                                   *
+ *                                                                            *
+ *****************************************************************************/
+
+.global kvmppc_handler_trampoline_enter
+kvmppc_handler_trampoline_enter:
+
+	/* Required state:
+	 *
+	 * MSR = ~IR|DR
+	 * R13 = PACA
+	 * R1 = host R1
+	 * R2 = host R2
+	 * R10 = guest MSR
+	 * all other volatile GPRS = free
+	 * SVCPU[CR] = guest CR
+	 * SVCPU[XER] = guest XER
+	 * SVCPU[CTR] = guest CTR
+	 * SVCPU[LR] = guest LR
+	 */
+
+	/* r3 = shadow vcpu */
+	GET_SHADOW_VCPU(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, SVCPU_IN_GUEST(r3)
+
+	/* Switch to guest segment. This is subarch specific. */
+	LOAD_GUEST_SEGMENTS
+
+	/* Enter guest */
+
+	PPC_LL	r4, (SVCPU_CTR)(r3)
+	PPC_LL	r5, (SVCPU_LR)(r3)
+	lwz	r6, (SVCPU_CR)(r3)
+	lwz	r7, (SVCPU_XER)(r3)
+
+	mtctr	r4
+	mtlr	r5
+	mtcr	r6
+	mtxer	r7
+
+	PPC_LL	r0, (SVCPU_R0)(r3)
+	PPC_LL	r1, (SVCPU_R1)(r3)
+	PPC_LL	r2, (SVCPU_R2)(r3)
+	PPC_LL	r4, (SVCPU_R4)(r3)
+	PPC_LL	r5, (SVCPU_R5)(r3)
+	PPC_LL	r6, (SVCPU_R6)(r3)
+	PPC_LL	r7, (SVCPU_R7)(r3)
+	PPC_LL	r8, (SVCPU_R8)(r3)
+	PPC_LL	r9, (SVCPU_R9)(r3)
+	PPC_LL	r10, (SVCPU_R10)(r3)
+	PPC_LL	r11, (SVCPU_R11)(r3)
+	PPC_LL	r12, (SVCPU_R12)(r3)
+	PPC_LL	r13, (SVCPU_R13)(r3)
+
+	PPC_LL	r3, (SVCPU_R3)(r3)
+
+	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
+	 * R12            = exit handler id
+	 * R13            = shadow vcpu - SHADOW_VCPU_OFF [=PACA on PPC64]
+	 * SVCPU.SCRATCH0 = guest R12
+	 * SVCPU.SCRATCH1 = guest CR
+	 *
+	 */
+
+	/* Save registers */
+
+	PPC_STL	r0, (SHADOW_VCPU_OFF + SVCPU_R0)(r13)
+	PPC_STL	r1, (SHADOW_VCPU_OFF + SVCPU_R1)(r13)
+	PPC_STL	r2, (SHADOW_VCPU_OFF + SVCPU_R2)(r13)
+	PPC_STL	r3, (SHADOW_VCPU_OFF + SVCPU_R3)(r13)
+	PPC_STL	r4, (SHADOW_VCPU_OFF + SVCPU_R4)(r13)
+	PPC_STL	r5, (SHADOW_VCPU_OFF + SVCPU_R5)(r13)
+	PPC_STL	r6, (SHADOW_VCPU_OFF + SVCPU_R6)(r13)
+	PPC_STL	r7, (SHADOW_VCPU_OFF + SVCPU_R7)(r13)
+	PPC_STL	r8, (SHADOW_VCPU_OFF + SVCPU_R8)(r13)
+	PPC_STL	r9, (SHADOW_VCPU_OFF + SVCPU_R9)(r13)
+	PPC_STL	r10, (SHADOW_VCPU_OFF + SVCPU_R10)(r13)
+	PPC_STL	r11, (SHADOW_VCPU_OFF + SVCPU_R11)(r13)
+
+	/* Restore R1/R2 so we can handle faults */
+	PPC_LL	r1, (SHADOW_VCPU_OFF + SVCPU_HOST_R1)(r13)
+	PPC_LL	r2, (SHADOW_VCPU_OFF + SVCPU_HOST_R2)(r13)
+
+	/* Save guest PC and MSR */
+	mfsrr0	r3
+	mfsrr1	r4
+
+	PPC_STL	r3, (SHADOW_VCPU_OFF + SVCPU_PC)(r13)
+	PPC_STL	r4, (SHADOW_VCPU_OFF + SVCPU_SHADOW_SRR1)(r13)
+
+	/* Get scratch'ed off registers */
+	mfspr	r9, SPRN_SPRG_SCRATCH0
+	PPC_LL	r8, (SHADOW_VCPU_OFF + SVCPU_SCRATCH0)(r13)
+	lwz	r7, (SHADOW_VCPU_OFF + SVCPU_SCRATCH1)(r13)
+
+	PPC_STL	r9, (SHADOW_VCPU_OFF + SVCPU_R13)(r13)
+	PPC_STL	r8, (SHADOW_VCPU_OFF + SVCPU_R12)(r13)
+	stw	r7, (SHADOW_VCPU_OFF + SVCPU_CR)(r13)
+
+	/* Save more register state  */
+
+	mfxer	r5
+	mfdar	r6
+	mfdsisr	r7
+	mfctr	r8
+	mflr	r9
+
+	stw	r5, (SHADOW_VCPU_OFF + SVCPU_XER)(r13)
+	PPC_STL	r6, (SHADOW_VCPU_OFF + SVCPU_FAULT_DAR)(r13)
+	stw	r7, (SHADOW_VCPU_OFF + SVCPU_FAULT_DSISR)(r13)
+	PPC_STL	r8, (SHADOW_VCPU_OFF + SVCPU_CTR)(r13)
+	PPC_STL	r9, (SHADOW_VCPU_OFF + SVCPU_LR)(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 */
+
+	/* In case lwz faults */
+	li	r0, KVM_INST_FETCH_FAILED
+
+#ifdef USE_QUICK_LAST_INST
+
+	/* Set guest mode to 'jump over instruction' so if lwz faults
+	 * we'll just continue at the next IP. */
+	li	r9, KVM_GUEST_MODE_SKIP
+	stb	r9, (SHADOW_VCPU_OFF + SVCPU_IN_GUEST)(r13)
+
+	/*    1) enable paging for data */
+	mfmsr	r9
+	ori	r11, r9, MSR_DR			/* Enable paging for data */
+	mtmsr	r11
+	sync
+	/*    2) fetch the instruction */
+	lwz	r0, 0(r3)
+	/*    3) disable paging again */
+	mtmsr	r9
+	sync
+
+#endif
+	stw	r0, (SHADOW_VCPU_OFF + SVCPU_LAST_INST)(r13)
+
+no_ld_last_inst:
+
+	/* Unset guest mode */
+	li	r9, KVM_GUEST_MODE_NONE
+	stb	r9, (SHADOW_VCPU_OFF + SVCPU_IN_GUEST)(r13)
+
+	/* Switch back to host MMU */
+	LOAD_HOST_SEGMENTS
+
+	/* Register usage at this point:
+	 *
+	 * R1       = host R1
+	 * R2       = host R2
+	 * R12      = exit handler id
+	 * R13      = shadow vcpu - SHADOW_VCPU_OFF [=PACA on PPC64]
+	 * SVCPU.*  = guest *
+	 *
+	 */
+
+	/* 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	r8, (SHADOW_VCPU_OFF + SVCPU_VMHANDLER)(r13)
+	mtsrr0	r8
+
+	RFI
+kvmppc_handler_trampoline_exit_end: