Commit f33e0702 authored by Nicholas Piggin's avatar Nicholas Piggin Committed by Michael Ellerman
Browse files

KVM: PPC: Book3S 64: Move GUEST_MODE_SKIP test into KVM 



Move the GUEST_MODE_SKIP logic into KVM code. This is quite a KVM
internal detail that has no real need to be in common handlers.

Add a comment explaining the what and why of KVM "skip" interrupts.

Signed-off-by: default avatarNicholas Piggin <npiggin@gmail.com>
Reviewed-by: default avatarDaniel Axtens <dja@axtens.net>
Reviewed-by: default avatarFabiano Rosas <farosas@linux.ibm.com>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210528090752.3542186-3-npiggin@gmail.com
parent f3601156

arch/powerpc/kernel/exceptions-64s.S

+0 −60
Original line number Diff line number Diff line
@@ -133,7 +133,6 @@ name: 
#define IBRANCH_TO_COMMON	.L_IBRANCH_TO_COMMON_\name\() /* ENTRY branch to common */

#define IREALMODE_COMMON	.L_IREALMODE_COMMON_\name\() /* Common runs in realmode */

#define IMASK		.L_IMASK_\name\()	/* IRQ soft-mask bit */

#define IKVM_SKIP	.L_IKVM_SKIP_\name\()	/* Generate KVM skip handler */

#define IKVM_REAL	.L_IKVM_REAL_\name\()	/* Real entry tests KVM */

#define __IKVM_REAL(name)	.L_IKVM_REAL_ ## name

#define IKVM_VIRT	.L_IKVM_VIRT_\name\()	/* Virt entry tests KVM */
@@ -190,9 +189,6 @@ do_define_int n 
	.ifndef IMASK

		IMASK=0

	.endif

	.ifndef IKVM_SKIP

		IKVM_SKIP=0

	.endif

	.ifndef IKVM_REAL

		IKVM_REAL=0

	.endif
@@ -250,15 +246,10 @@ do_define_int n 
	.balign IFETCH_ALIGN_BYTES

\name\()_kvm:



	.if IKVM_SKIP

	cmpwi	r10,KVM_GUEST_MODE_SKIP

	beq	89f

	.else

BEGIN_FTR_SECTION

	ld	r10,IAREA+EX_CFAR(r13)

	std	r10,HSTATE_CFAR(r13)

END_FTR_SECTION_IFSET(CPU_FTR_CFAR)

	.endif



	ld	r10,IAREA+EX_CTR(r13)

	mtctr	r10
@@ -285,27 +276,6 @@ END_FTR_SECTION_IFSET(CPU_FTR_HAS_PPR) 
	ori	r12,r12,(IVEC)

	.endif

	b	kvmppc_interrupt



	.if IKVM_SKIP

89:	mtocrf	0x80,r9

	ld	r10,IAREA+EX_CTR(r13)

	mtctr	r10

	ld	r9,IAREA+EX_R9(r13)

	ld	r10,IAREA+EX_R10(r13)

	ld	r11,IAREA+EX_R11(r13)

	ld	r12,IAREA+EX_R12(r13)

	.if IHSRR_IF_HVMODE

	BEGIN_FTR_SECTION

	b	kvmppc_skip_Hinterrupt

	FTR_SECTION_ELSE

	b	kvmppc_skip_interrupt

	ALT_FTR_SECTION_END_IFSET(CPU_FTR_HVMODE | CPU_FTR_ARCH_206)

	.elseif IHSRR

	b	kvmppc_skip_Hinterrupt

	.else

	b	kvmppc_skip_interrupt

	.endif

	.endif

.endm



#else
@@ -1064,7 +1034,6 @@ INT_DEFINE_BEGIN(machine_check) 
	ISET_RI=0

	IDAR=1

	IDSISR=1

	IKVM_SKIP=1

	IKVM_REAL=1

INT_DEFINE_END(machine_check)
@@ -1336,7 +1305,6 @@ INT_DEFINE_BEGIN(data_access) 
	IVEC=0x300

	IDAR=1

	IDSISR=1

	IKVM_SKIP=1

	IKVM_REAL=1

INT_DEFINE_END(data_access)
@@ -1390,7 +1358,6 @@ ALT_MMU_FTR_SECTION_END_IFCLR(MMU_FTR_TYPE_RADIX) 
INT_DEFINE_BEGIN(data_access_slb)

	IVEC=0x380

	IDAR=1

	IKVM_SKIP=1

	IKVM_REAL=1

INT_DEFINE_END(data_access_slb)
@@ -2057,7 +2024,6 @@ INT_DEFINE_BEGIN(h_data_storage) 
	IHSRR=1

	IDAR=1

	IDSISR=1

	IKVM_SKIP=1

	IKVM_REAL=1

	IKVM_VIRT=1

INT_DEFINE_END(h_data_storage)
@@ -3003,32 +2969,6 @@ EXPORT_SYMBOL(do_uaccess_flush) 
MASKED_INTERRUPT

MASKED_INTERRUPT hsrr=1



#ifdef CONFIG_KVM_BOOK3S_64_HANDLER

kvmppc_skip_interrupt:

	/*

	 * Here all GPRs are unchanged from when the interrupt happened

	 * except for r13, which is saved in SPRG_SCRATCH0.

	 */

	mfspr	r13, SPRN_SRR0

	addi	r13, r13, 4

	mtspr	SPRN_SRR0, r13

	GET_SCRATCH0(r13)

	RFI_TO_KERNEL

	b	.



kvmppc_skip_Hinterrupt:

	/*

	 * Here all GPRs are unchanged from when the interrupt happened

	 * except for r13, which is saved in SPRG_SCRATCH0.

	 */

	mfspr	r13, SPRN_HSRR0

	addi	r13, r13, 4

	mtspr	SPRN_HSRR0, r13

	GET_SCRATCH0(r13)

	HRFI_TO_KERNEL

	b	.

#endif



	/*

	 * Relocation-on interrupts: A subset of the interrupts can be delivered

	 * with IR=1/DR=1, if AIL==2 and MSR.HV won't be changed by delivering

arch/powerpc/kvm/book3s_64_entry.S

+58 −1
Original line number Diff line number Diff line 
/* SPDX-License-Identifier: GPL-2.0-only */

#include <asm/asm-offsets.h>

#include <asm/cache.h>

#include <asm/exception-64s.h>

#include <asm/kvm_asm.h>

#include <asm/kvm_book3s_asm.h>

#include <asm/ppc_asm.h>
@@ -20,9 +21,12 @@ kvmppc_interrupt: 
	 * guest R12 saved in shadow VCPU SCRATCH0

	 * guest R13 saved in SPRN_SCRATCH0

	 */

#ifdef CONFIG_KVM_BOOK3S_HV_POSSIBLE

	std	r9,HSTATE_SCRATCH2(r13)

	lbz	r9,HSTATE_IN_GUEST(r13)

	cmpwi	r9,KVM_GUEST_MODE_SKIP

	beq-	.Lmaybe_skip

.Lno_skip:

#ifdef CONFIG_KVM_BOOK3S_HV_POSSIBLE

	cmpwi	r9,KVM_GUEST_MODE_HOST_HV

	beq	kvmppc_bad_host_intr

#ifdef CONFIG_KVM_BOOK3S_PR_POSSIBLE
@@ -32,5 +36,58 @@ kvmppc_interrupt: 
#endif

	b	kvmppc_interrupt_hv

#else

	ld	r9,HSTATE_SCRATCH2(r13)

	b	kvmppc_interrupt_pr

#endif



/*

 * "Skip" interrupts are part of a trick KVM uses a with hash guests to load

 * the faulting instruction in guest memory from the the hypervisor without

 * walking page tables.

 *

 * When the guest takes a fault that requires the hypervisor to load the

 * instruction (e.g., MMIO emulation), KVM is running in real-mode with HV=1

 * and the guest MMU context loaded. It sets KVM_GUEST_MODE_SKIP, and sets

 * MSR[DR]=1 while leaving MSR[IR]=0, so it continues to fetch HV instructions

 * but loads and stores will access the guest context. This is used to load

 * the faulting instruction using the faulting guest effective address.

 *

 * However the guest context may not be able to translate, or it may cause a

 * machine check or other issue, which results in a fault in the host

 * (even with KVM-HV).

 *

 * These faults come here because KVM_GUEST_MODE_SKIP was set, so if they

 * are (or are likely) caused by that load, the instruction is skipped by

 * just returning with the PC advanced +4, where it is noticed the load did

 * not execute and it goes to the slow path which walks the page tables to

 * read guest memory.

 */

.Lmaybe_skip:

	cmpwi	r12,BOOK3S_INTERRUPT_MACHINE_CHECK

	beq	1f

	cmpwi	r12,BOOK3S_INTERRUPT_DATA_STORAGE

	beq	1f

	cmpwi	r12,BOOK3S_INTERRUPT_DATA_SEGMENT

	beq	1f

#ifdef CONFIG_KVM_BOOK3S_HV_POSSIBLE

	/* HSRR interrupts get 2 added to interrupt number */

	cmpwi	r12,BOOK3S_INTERRUPT_H_DATA_STORAGE | 0x2

	beq	2f

#endif

	b	.Lno_skip

1:	mfspr	r9,SPRN_SRR0

	addi	r9,r9,4

	mtspr	SPRN_SRR0,r9

	ld	r12,HSTATE_SCRATCH0(r13)

	ld	r9,HSTATE_SCRATCH2(r13)

	GET_SCRATCH0(r13)

	RFI_TO_KERNEL

#ifdef CONFIG_KVM_BOOK3S_HV_POSSIBLE

2:	mfspr	r9,SPRN_HSRR0

	addi	r9,r9,4

	mtspr	SPRN_HSRR0,r9

	ld	r12,HSTATE_SCRATCH0(r13)

	ld	r9,HSTATE_SCRATCH2(r13)

	GET_SCRATCH0(r13)

	HRFI_TO_KERNEL

#endif