Commit 51f04726 authored by Mihai Caraman's avatar Mihai Caraman Committed by Alexander Graf
Browse files

KVM: PPC: Allow kvmppc_get_last_inst() to fail 



On book3e, guest last instruction is read on the exit path using load
external pid (lwepx) dedicated instruction. This load operation may fail
due to TLB eviction and execute-but-not-read entries.

This patch lay down the path for an alternative solution to read the guest
last instruction, by allowing kvmppc_get_lat_inst() function to fail.
Architecture specific implmentations of kvmppc_load_last_inst() may read
last guest instruction and instruct the emulation layer to re-execute the
guest in case of failure.

Make kvmppc_get_last_inst() definition common between architectures.

Signed-off-by: default avatarMihai Caraman <mihai.caraman@freescale.com>
Signed-off-by: default avatarAlexander Graf <agraf@suse.de>
parent 9a26af64

arch/powerpc/include/asm/kvm_book3s.h

+0 −26
Original line number Diff line number Diff line
@@ -276,32 +276,6 @@ static inline bool kvmppc_need_byteswap(struct kvm_vcpu *vcpu) 
	return (kvmppc_get_msr(vcpu) & MSR_LE) != (MSR_KERNEL & MSR_LE);

}



static inline u32 kvmppc_get_last_inst_internal(struct kvm_vcpu *vcpu, ulong pc)

{

	/* Load the instruction manually if it failed to do so in the

	 * exit path */

	if (vcpu->arch.last_inst == KVM_INST_FETCH_FAILED)

		kvmppc_ld(vcpu, &pc, sizeof(u32), &vcpu->arch.last_inst, false);



	return kvmppc_need_byteswap(vcpu) ? swab32(vcpu->arch.last_inst) :

		vcpu->arch.last_inst;

}



static inline u32 kvmppc_get_last_inst(struct kvm_vcpu *vcpu)

{

	return kvmppc_get_last_inst_internal(vcpu, kvmppc_get_pc(vcpu));

}



/*

 * Like kvmppc_get_last_inst(), but for fetching a sc instruction.

 * Because the sc instruction sets SRR0 to point to the following

 * instruction, we have to fetch from pc - 4.

 */

static inline u32 kvmppc_get_last_sc(struct kvm_vcpu *vcpu)

{

	return kvmppc_get_last_inst_internal(vcpu, kvmppc_get_pc(vcpu) - 4);

}



static inline ulong kvmppc_get_fault_dar(struct kvm_vcpu *vcpu)

{

	return vcpu->arch.fault_dar;

arch/powerpc/include/asm/kvm_booke.h

+0 −5
Original line number Diff line number Diff line
@@ -69,11 +69,6 @@ static inline bool kvmppc_need_byteswap(struct kvm_vcpu *vcpu) 
	return false;

}



static inline u32 kvmppc_get_last_inst(struct kvm_vcpu *vcpu)

{

	return vcpu->arch.last_inst;

}



static inline void kvmppc_set_ctr(struct kvm_vcpu *vcpu, ulong val)

{

	vcpu->arch.ctr = val;

arch/powerpc/include/asm/kvm_ppc.h

+31 −0
Original line number Diff line number Diff line
@@ -47,6 +47,11 @@ enum emulation_result { 
	EMULATE_EXIT_USER,    /* emulation requires exit to user-space */

};



enum instruction_type {

	INST_GENERIC,

	INST_SC,		/* system call */

};



extern int kvmppc_vcpu_run(struct kvm_run *kvm_run, struct kvm_vcpu *vcpu);

extern int __kvmppc_vcpu_run(struct kvm_run *kvm_run, struct kvm_vcpu *vcpu);

extern void kvmppc_handler_highmem(void);
@@ -62,6 +67,9 @@ extern int kvmppc_handle_store(struct kvm_run *run, struct kvm_vcpu *vcpu, 
			       u64 val, unsigned int bytes,

			       int is_default_endian);



extern int kvmppc_load_last_inst(struct kvm_vcpu *vcpu,

				 enum instruction_type type, u32 *inst);



extern int kvmppc_emulate_instruction(struct kvm_run *run,

                                      struct kvm_vcpu *vcpu);

extern int kvmppc_emulate_mmio(struct kvm_run *run, struct kvm_vcpu *vcpu);
@@ -234,6 +242,29 @@ struct kvmppc_ops { 
extern struct kvmppc_ops *kvmppc_hv_ops;

extern struct kvmppc_ops *kvmppc_pr_ops;



static inline int kvmppc_get_last_inst(struct kvm_vcpu *vcpu,

					enum instruction_type type, u32 *inst)

{

	int ret = EMULATE_DONE;

	u32 fetched_inst;



	/* Load the instruction manually if it failed to do so in the

	 * exit path */

	if (vcpu->arch.last_inst == KVM_INST_FETCH_FAILED)

		ret = kvmppc_load_last_inst(vcpu, type, &vcpu->arch.last_inst);



	/*  Write fetch_failed unswapped if the fetch failed */

	if (ret == EMULATE_DONE)

		fetched_inst = kvmppc_need_byteswap(vcpu) ?

				swab32(vcpu->arch.last_inst) :

				vcpu->arch.last_inst;

	else

		fetched_inst = vcpu->arch.last_inst;



	*inst = fetched_inst;

	return ret;

}



static inline bool is_kvmppc_hv_enabled(struct kvm *kvm)

{

	return kvm->arch.kvm_ops == kvmppc_hv_ops;

arch/powerpc/kvm/book3s.c

+17 −0
Original line number Diff line number Diff line
@@ -488,6 +488,23 @@ mmio: 
}

EXPORT_SYMBOL_GPL(kvmppc_ld);



int kvmppc_load_last_inst(struct kvm_vcpu *vcpu, enum instruction_type type,

					 u32 *inst)

{

	ulong pc = kvmppc_get_pc(vcpu);

	int r;



	if (type == INST_SC)

		pc -= 4;



	r = kvmppc_ld(vcpu, &pc, sizeof(u32), inst, false);

	if (r == EMULATE_DONE)

		return r;

	else

		return EMULATE_AGAIN;

}

EXPORT_SYMBOL_GPL(kvmppc_load_last_inst);



int kvm_arch_vcpu_setup(struct kvm_vcpu *vcpu)

{

	return 0;

arch/powerpc/kvm/book3s_64_mmu_hv.c

+5 −12
Original line number Diff line number Diff line
@@ -530,21 +530,14 @@ static int instruction_is_store(unsigned int instr) 
static int kvmppc_hv_emulate_mmio(struct kvm_run *run, struct kvm_vcpu *vcpu,

				  unsigned long gpa, gva_t ea, int is_store)

{

	int ret;

	u32 last_inst;

	unsigned long srr0 = kvmppc_get_pc(vcpu);



	/* We try to load the last instruction.  We don't let

	 * emulate_instruction do it as it doesn't check what

	 * kvmppc_ld returns.

	/*

	 * If we fail, we just return to the guest and try executing it again.

	 */

	if (vcpu->arch.last_inst == KVM_INST_FETCH_FAILED) {

		ret = kvmppc_ld(vcpu, &srr0, sizeof(u32), &last_inst, false);

		if (ret != EMULATE_DONE || last_inst == KVM_INST_FETCH_FAILED)

	if (kvmppc_get_last_inst(vcpu, INST_GENERIC, &last_inst) !=

		EMULATE_DONE)

		return RESUME_GUEST;

		vcpu->arch.last_inst = last_inst;

	}



	/*

	 * WARNING: We do not know for sure whether the instruction we just
@@ -558,7 +551,7 @@ static int kvmppc_hv_emulate_mmio(struct kvm_run *run, struct kvm_vcpu *vcpu, 
	 * we just return and retry the instruction.

	 */



	if (instruction_is_store(kvmppc_get_last_inst(vcpu)) != !!is_store)

	if (instruction_is_store(last_inst) != !!is_store)

		return RESUME_GUEST;



	/*

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