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KVM: MIPS: Implement HYPCALL emulation

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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: James Hogan <james.hogan@imgtec.com>
Acked-by: Ralf 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
This commit is contained in:
James Hogan
2017-03-14 10:15:14 +00:00
parent a6c09b9f9d
commit 955d8dc3ee
7 changed files with 74 additions and 1 deletions
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53
arch/mips/kvm/hypcall.c Normal file
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/*
* This file is subject to the terms and conditions of the GNU General Public
* License. See the file "COPYING" in the main directory of this archive
* for more details.
*
* KVM/MIPS: Hypercall handling.
*
* Copyright (C) 2015 Imagination Technologies Ltd.
*/
#include <linux/kernel.h>
#include <linux/kvm_host.h>
#include <linux/kvm_para.h>
#define MAX_HYPCALL_ARGS 4
enum emulation_result kvm_mips_emul_hypcall(struct kvm_vcpu *vcpu,
union mips_instruction inst)
{
unsigned int code = (inst.co_format.code >> 5) & 0x3ff;
kvm_debug("[%#lx] HYPCALL %#03x\n", vcpu->arch.pc, code);
switch (code) {
case 0:
return EMULATE_HYPERCALL;
default:
return EMULATE_FAIL;
};
}
static int kvm_mips_hypercall(struct kvm_vcpu *vcpu, unsigned long num,
const unsigned long *args, unsigned long *hret)
{
/* Report unimplemented hypercall to guest */
*hret = -KVM_ENOSYS;
return RESUME_GUEST;
}
int kvm_mips_handle_hypcall(struct kvm_vcpu *vcpu)
{
unsigned long num, args[MAX_HYPCALL_ARGS];
/* read hypcall number and arguments */
num = vcpu->arch.gprs[2]; /* v0 */
args[0] = vcpu->arch.gprs[4]; /* a0 */
args[1] = vcpu->arch.gprs[5]; /* a1 */
args[2] = vcpu->arch.gprs[6]; /* a2 */
args[3] = vcpu->arch.gprs[7]; /* a3 */
return kvm_mips_hypercall(vcpu, num,
args, &vcpu->arch.gprs[2] /* v0 */);
}