Commit 955d8dc3 authored by James Hogan's avatar James Hogan
Browse files

KVM: MIPS: Implement HYPCALL emulation 



Emulate the HYPCALL instruction added in the VZ ASE and used by the MIPS
paravirtualised guest support that is already merged. The new hypcall.c
handles arguments and the return value. No actual hypercalls are yet
supported, but this still allows us to safely step over hypercalls and
set an error code in the return value for forward compatibility.

Non-zero HYPCALL codes are not handled.

We also document the hypercall ABI which asm/kvm_para.h uses.

Signed-off-by: default avatarJames Hogan <james.hogan@imgtec.com>
Acked-by: default avatarRalf Baechle <ralf@linux-mips.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Radim Krčmář" <rkrcmar@redhat.com>
Cc: Andreas Herrmann <andreas.herrmann@caviumnetworks.com>
Cc: David Daney <david.daney@cavium.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: linux-mips@linux-mips.org
Cc: kvm@vger.kernel.org
Cc: linux-doc@vger.kernel.org
parent a6c09b9f

Documentation/virtual/kvm/hypercalls.txt

+5 −0
Original line number Diff line number Diff line
@@ -28,6 +28,11 @@ S390: 
  property inside the device tree's /hypervisor node.

  For more information refer to Documentation/virtual/kvm/ppc-pv.txt



MIPS:

  KVM hypercalls use the HYPCALL instruction with code 0 and the hypercall

  number in $2 (v0). Up to four arguments may be placed in $4-$7 (a0-a3) and

  the return value is placed in $2 (v0).



KVM Hypercalls Documentation

===========================

The template for each hypercall is:

arch/mips/include/asm/kvm_host.h

+7 −0
Original line number Diff line number Diff line
@@ -229,6 +229,7 @@ enum emulation_result { 
	EMULATE_WAIT,		/* WAIT instruction */

	EMULATE_PRIV_FAIL,

	EMULATE_EXCEPT,		/* A guest exception has been generated */

	EMULATE_HYPERCALL,	/* HYPCALL instruction */

};



#define mips3_paddr_to_tlbpfn(x) \
@@ -832,6 +833,12 @@ unsigned int kvm_mips_config3_wrmask(struct kvm_vcpu *vcpu); 
unsigned int kvm_mips_config4_wrmask(struct kvm_vcpu *vcpu);

unsigned int kvm_mips_config5_wrmask(struct kvm_vcpu *vcpu);



/* Hypercalls (hypcall.c) */



enum emulation_result kvm_mips_emul_hypcall(struct kvm_vcpu *vcpu,

					    union mips_instruction inst);

int kvm_mips_handle_hypcall(struct kvm_vcpu *vcpu);



/* Dynamic binary translation */

extern int kvm_mips_trans_cache_index(union mips_instruction inst,

				      u32 *opc, struct kvm_vcpu *vcpu);

arch/mips/include/uapi/asm/inst.h

+1 −1
Original line number Diff line number Diff line
@@ -179,7 +179,7 @@ enum cop0_coi_func { 
	tlbr_op	      = 0x01, tlbwi_op	    = 0x02,

	tlbwr_op      = 0x06, tlbp_op	    = 0x08,

	rfe_op	      = 0x10, eret_op	    = 0x18,

	wait_op       = 0x20,

	wait_op       = 0x20, hypcall_op    = 0x28

};



/*

arch/mips/kvm/Makefile

+1 −0
Original line number Diff line number Diff line
@@ -10,6 +10,7 @@ common-objs-$(CONFIG_CPU_HAS_MSA) += msa.o 
kvm-objs := $(common-objs-y) mips.o emulate.o entry.o \

	    interrupt.o stats.o commpage.o \

	    dyntrans.o trap_emul.o fpu.o

kvm-objs += hypcall.o

kvm-objs += mmu.o



obj-$(CONFIG_KVM)	+= kvm.o

arch/mips/kvm/emulate.c

+3 −0
Original line number Diff line number Diff line
@@ -1143,6 +1143,9 @@ enum emulation_result kvm_mips_emulate_CP0(union mips_instruction inst, 
		case wait_op:

			er = kvm_mips_emul_wait(vcpu);

			break;

		case hypcall_op:

			er = kvm_mips_emul_hypcall(vcpu, inst);

			break;

		}

	} else {

		rt = inst.c0r_format.rt;

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