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Date:   Thu, 16 Jan 2020 15:37:08 -0800 (PST)
From:   Palmer Dabbelt <palmerdabbelt@google.com>
Subject:     Re: [PATCH v10 04/19] RISC-V: Add initial skeletal KVM support
CC:     Paul Walmsley <paul.walmsley@sifive.com>, aou@eecs.berkeley.edu,
        pbonzini@redhat.com, rkrcmar@redhat.com, graf@amazon.com,
        Atish Patra <Atish.Patra@wdc.com>,
        Alistair Francis <Alistair.Francis@wdc.com>,
        Damien Le Moal <Damien.LeMoal@wdc.com>,
        Christoph Hellwig <hch@lst.de>, anup@brainfault.org,
        kvm@vger.kernel.org, kvm-riscv@lists.infradead.org,
        linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org,
        Anup Patel <Anup.Patel@wdc.com>
To:     Anup Patel <Anup.Patel@wdc.com>
In-Reply-To: <20191223113443.68969-5-anup.patel@wdc.com>
References: <20191223113443.68969-5-anup.patel@wdc.com>
  <20191223113443.68969-1-anup.patel@wdc.com>
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On Mon, 23 Dec 2019 03:35:46 PST (-0800), Anup Patel wrote:
> This patch adds initial skeletal KVM RISC-V support which has:
> 1. A simple implementation of arch specific VM functions
>    except kvm_vm_ioctl_get_dirty_log() which will implemeted
>    in-future as part of stage2 page loging.
> 2. Stubs of required arch specific VCPU functions except
>    kvm_arch_vcpu_ioctl_run() which is semi-complete and
>    extended by subsequent patches.
> 3. Stubs for required arch specific stage2 MMU functions.
>
> Signed-off-by: Anup Patel <anup.patel@wdc.com>
> Acked-by: Paolo Bonzini <pbonzini@redhat.com>
> Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
> Reviewed-by: Alexander Graf <graf@amazon.com>
> ---
>  arch/riscv/Kconfig                |   2 +
>  arch/riscv/Makefile               |   2 +
>  arch/riscv/include/asm/kvm_host.h |  82 ++++++++
>  arch/riscv/include/uapi/asm/kvm.h |  47 +++++
>  arch/riscv/kvm/Kconfig            |  33 ++++
>  arch/riscv/kvm/Makefile           |  13 ++
>  arch/riscv/kvm/main.c             |  93 +++++++++
>  arch/riscv/kvm/mmu.c              |  83 ++++++++
>  arch/riscv/kvm/vcpu.c             | 316 ++++++++++++++++++++++++++++++
>  arch/riscv/kvm/vcpu_exit.c        |  36 ++++
>  arch/riscv/kvm/vm.c               |  79 ++++++++
>  11 files changed, 786 insertions(+)
>  create mode 100644 arch/riscv/include/asm/kvm_host.h
>  create mode 100644 arch/riscv/include/uapi/asm/kvm.h
>  create mode 100644 arch/riscv/kvm/Kconfig
>  create mode 100644 arch/riscv/kvm/Makefile
>  create mode 100644 arch/riscv/kvm/main.c
>  create mode 100644 arch/riscv/kvm/mmu.c
>  create mode 100644 arch/riscv/kvm/vcpu.c
>  create mode 100644 arch/riscv/kvm/vcpu_exit.c
>  create mode 100644 arch/riscv/kvm/vm.c
>
> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> index baf0943c80d0..2e8551a9cd32 100644
> --- a/arch/riscv/Kconfig
> +++ b/arch/riscv/Kconfig
> @@ -366,3 +366,5 @@ menu "Power management options"
>  source "kernel/power/Kconfig"
>  
>  endmenu
> +
> +source "arch/riscv/kvm/Kconfig"
> diff --git a/arch/riscv/Makefile b/arch/riscv/Makefile
> index b9009a2fbaf5..65b58cec9abd 100644
> --- a/arch/riscv/Makefile
> +++ b/arch/riscv/Makefile
> @@ -77,6 +77,8 @@ head-y := arch/riscv/kernel/head.o
>  
>  core-y += arch/riscv/
>  
> +core-$(CONFIG_KVM) += arch/riscv/kvm/
> +
>  libs-y += arch/riscv/lib/
>  
>  PHONY += vdso_install
> diff --git a/arch/riscv/include/asm/kvm_host.h b/arch/riscv/include/asm/kvm_host.h
> new file mode 100644
> index 000000000000..e0b633f616a4
> --- /dev/null
> +++ b/arch/riscv/include/asm/kvm_host.h
> @@ -0,0 +1,82 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * Copyright (C) 2019 Western Digital Corporation or its affiliates.
> + *
> + * Authors:
> + *     Anup Patel <anup.patel@wdc.com>
> + */
> +
> +#ifndef __RISCV_KVM_HOST_H__
> +#define __RISCV_KVM_HOST_H__
> +
> +#include <linux/types.h>
> +#include <linux/kvm.h>
> +#include <linux/kvm_types.h>
> +
> +#ifdef CONFIG_64BIT
> +#define KVM_MAX_VCPUS			(1U << 16)
> +#else
> +#define KVM_MAX_VCPUS			(1U << 9)
> +#endif
> +
> +#define KVM_USER_MEM_SLOTS		512
> +#define KVM_HALT_POLL_NS_DEFAULT	500000
> +
> +#define KVM_VCPU_MAX_FEATURES		0
> +
> +#define KVM_REQ_SLEEP \
> +	KVM_ARCH_REQ_FLAGS(0, KVM_REQUEST_WAIT | KVM_REQUEST_NO_WAKEUP)
> +#define KVM_REQ_VCPU_RESET		KVM_ARCH_REQ(1)
> +
> +struct kvm_vm_stat {
> +	ulong remote_tlb_flush;
> +};
> +
> +struct kvm_vcpu_stat {
> +	u64 halt_successful_poll;
> +	u64 halt_attempted_poll;
> +	u64 halt_poll_invalid;
> +	u64 halt_wakeup;
> +	u64 ecall_exit_stat;
> +	u64 wfi_exit_stat;
> +	u64 mmio_exit_user;
> +	u64 mmio_exit_kernel;
> +	u64 exits;
> +};

Presumably at least this came from arm64, as it's exactly the same.  If that's
the case then this file, and probably a bunch of others, should be attributed
somehow.  IIRC we left the copyrights in our copied files and it looks like
arch/arm64 has done the same:

    $ head -n10 arch/arm64/include/asm/kvm_host.h 
    /* SPDX-License-Identifier: GPL-2.0-only */
    /*
     * Copyright (C) 2012,2013 - ARM Ltd
     * Author: Marc Zyngier <marc.zyngier@arm.com>
     *
     * Derived from arch/arm/include/asm/kvm_host.h:
     * Copyright (C) 2012 - Virtual Open Systems and Columbia University
     * Author: Christoffer Dall <c.dall@virtualopensystems.com>
     */

> +
> +struct kvm_arch_memory_slot {
> +};
> +
> +struct kvm_arch {
> +	/* stage2 page table */
> +	pgd_t *pgd;
> +	phys_addr_t pgd_phys;
> +};
> +
> +struct kvm_vcpu_arch {
> +	/* Don't run the VCPU (blocked) */
> +	bool pause;
> +
> +	/* SRCU lock index for in-kernel run loop */
> +	int srcu_idx;
> +};
> +
> +static inline void kvm_arch_hardware_unsetup(void) {}
> +static inline void kvm_arch_sync_events(struct kvm *kvm) {}
> +static inline void kvm_arch_vcpu_uninit(struct kvm_vcpu *vcpu) {}
> +static inline void kvm_arch_sched_in(struct kvm_vcpu *vcpu, int cpu) {}
> +static inline void kvm_arch_vcpu_block_finish(struct kvm_vcpu *vcpu) {}
> +
> +void kvm_riscv_stage2_flush_cache(struct kvm_vcpu *vcpu);
> +int kvm_riscv_stage2_alloc_pgd(struct kvm *kvm);
> +void kvm_riscv_stage2_free_pgd(struct kvm *kvm);
> +void kvm_riscv_stage2_update_hgatp(struct kvm_vcpu *vcpu);
> +
> +int kvm_riscv_vcpu_mmio_return(struct kvm_vcpu *vcpu, struct kvm_run *run);
> +int kvm_riscv_vcpu_exit(struct kvm_vcpu *vcpu, struct kvm_run *run,
> +			unsigned long scause, unsigned long stval,
> +			unsigned long htval, unsigned long htinst);
> +
> +static inline void __kvm_riscv_switch_to(struct kvm_vcpu_arch *vcpu_arch) {}
> +
> +#endif /* __RISCV_KVM_HOST_H__ */
> diff --git a/arch/riscv/include/uapi/asm/kvm.h b/arch/riscv/include/uapi/asm/kvm.h
> new file mode 100644
> index 000000000000..d15875818b6e
> --- /dev/null
> +++ b/arch/riscv/include/uapi/asm/kvm.h
> @@ -0,0 +1,47 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/*
> + * Copyright (C) 2019 Western Digital Corporation or its affiliates.
> + *
> + * Authors:
> + *     Anup Patel <anup.patel@wdc.com>
> + */
> +
> +#ifndef __LINUX_KVM_RISCV_H
> +#define __LINUX_KVM_RISCV_H
> +
> +#ifndef __ASSEMBLY__
> +
> +#include <linux/types.h>
> +#include <asm/ptrace.h>
> +
> +#define __KVM_HAVE_READONLY_MEM
> +
> +#define KVM_COALESCED_MMIO_PAGE_OFFSET 1
> +
> +/* for KVM_GET_REGS and KVM_SET_REGS */
> +struct kvm_regs {
> +};
> +
> +/* for KVM_GET_FPU and KVM_SET_FPU */
> +struct kvm_fpu {
> +};
> +
> +/* KVM Debug exit structure */
> +struct kvm_debug_exit_arch {
> +};
> +
> +/* for KVM_SET_GUEST_DEBUG */
> +struct kvm_guest_debug_arch {
> +};
> +
> +/* definition of registers in kvm_run */
> +struct kvm_sync_regs {
> +};
> +
> +/* dummy definition */
> +struct kvm_sregs {
> +};
> +
> +#endif
> +
> +#endif /* __LINUX_KVM_RISCV_H */
> diff --git a/arch/riscv/kvm/Kconfig b/arch/riscv/kvm/Kconfig
> new file mode 100644
> index 000000000000..88edd477b3a8
> --- /dev/null
> +++ b/arch/riscv/kvm/Kconfig
> @@ -0,0 +1,33 @@
> +# SPDX-License-Identifier: GPL-2.0
> +#
> +# KVM configuration
> +#
> +
> +source "virt/kvm/Kconfig"
> +
> +menuconfig VIRTUALIZATION
> +	bool "Virtualization"
> +	help
> +	  Say Y here to get to see options for using your Linux host to run
> +	  other operating systems inside virtual machines (guests).
> +	  This option alone does not add any kernel code.
> +
> +	  If you say N, all options in this submenu will be skipped and
> +	  disabled.
> +
> +if VIRTUALIZATION
> +
> +config KVM
> +	tristate "Kernel-based Virtual Machine (KVM) support (EXPERIMENTAL)"
> +	depends on RISCV_SBI && MMU
> +	select PREEMPT_NOTIFIERS
> +	select ANON_INODES
> +	select KVM_MMIO
> +	select HAVE_KVM_VCPU_ASYNC_IOCTL
> +	select SRCU
> +	help
> +	  Support hosting virtualized guest machines.
> +
> +	  If unsure, say N.
> +
> +endif # VIRTUALIZATION
> diff --git a/arch/riscv/kvm/Makefile b/arch/riscv/kvm/Makefile
> new file mode 100644
> index 000000000000..37b5a59d4f4f
> --- /dev/null
> +++ b/arch/riscv/kvm/Makefile
> @@ -0,0 +1,13 @@
> +# SPDX-License-Identifier: GPL-2.0
> +# Makefile for RISC-V KVM support
> +#
> +
> +common-objs-y = $(addprefix ../../../virt/kvm/, kvm_main.o coalesced_mmio.o)
> +
> +ccflags-y := -Ivirt/kvm -Iarch/riscv/kvm
> +
> +kvm-objs := $(common-objs-y)
> +
> +kvm-objs += main.o vm.o mmu.o vcpu.o vcpu_exit.o
> +
> +obj-$(CONFIG_KVM)	+= kvm.o
> diff --git a/arch/riscv/kvm/main.c b/arch/riscv/kvm/main.c
> new file mode 100644
> index 000000000000..f29768c82fbe
> --- /dev/null
> +++ b/arch/riscv/kvm/main.c
> @@ -0,0 +1,93 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (C) 2019 Western Digital Corporation or its affiliates.
> + *
> + * Authors:
> + *     Anup Patel <anup.patel@wdc.com>
> + */
> +
> +#include <linux/errno.h>
> +#include <linux/err.h>
> +#include <linux/module.h>
> +#include <linux/kvm_host.h>
> +#include <asm/csr.h>
> +#include <asm/hwcap.h>
> +#include <asm/sbi.h>
> +
> +long kvm_arch_dev_ioctl(struct file *filp,
> +			unsigned int ioctl, unsigned long arg)
> +{
> +	return -EINVAL;
> +}
> +
> +int kvm_arch_check_processor_compat(void)
> +{
> +	return 0;
> +}
> +
> +int kvm_arch_hardware_setup(void)
> +{
> +	return 0;
> +}
> +
> +int kvm_arch_hardware_enable(void)
> +{
> +	unsigned long hideleg, hedeleg;
> +
> +	hedeleg = 0;
> +	hedeleg |= (1UL << EXC_INST_MISALIGNED);
> +	hedeleg |= (1UL << EXC_BREAKPOINT);
> +	hedeleg |= (1UL << EXC_SYSCALL);
> +	hedeleg |= (1UL << EXC_INST_PAGE_FAULT);
> +	hedeleg |= (1UL << EXC_LOAD_PAGE_FAULT);
> +	hedeleg |= (1UL << EXC_STORE_PAGE_FAULT);
> +	csr_write(CSR_HEDELEG, hedeleg);
> +
> +	hideleg = 0;
> +	hideleg |= (1UL << IRQ_S_SOFT);
> +	hideleg |= (1UL << IRQ_S_TIMER);
> +	hideleg |= (1UL << IRQ_S_EXT);
> +	csr_write(CSR_HIDELEG, hideleg);
> +
> +	csr_write(CSR_HIP, 0);
> +
> +	return 0;
> +}
> +
> +void kvm_arch_hardware_disable(void)
> +{
> +	csr_write(CSR_HEDELEG, 0);
> +	csr_write(CSR_HIDELEG, 0);
> +}
> +
> +int kvm_arch_init(void *opaque)
> +{
> +	if (!riscv_isa_extension_available(NULL, h)) {
> +		kvm_info("hypervisor extension not available\n");
> +		return -ENODEV;
> +	}
> +
> +	if (sbi_spec_is_0_1()) {
> +		kvm_info("require SBI v0.2 or higher\n");
> +		return -ENODEV;
> +	}
> +
> +	if (sbi_probe_extension(SBI_EXT_RFENCE) <= 0) {
> +		kvm_info("require SBI RFENCE extension\n");
> +		return -ENODEV;
> +	}
> +
> +	kvm_info("hypervisor extension available\n");
> +
> +	return 0;
> +}
> +
> +void kvm_arch_exit(void)
> +{
> +}
> +
> +static int riscv_kvm_init(void)
> +{
> +	return kvm_init(NULL, sizeof(struct kvm_vcpu), 0, THIS_MODULE);
> +}
> +module_init(riscv_kvm_init);
> diff --git a/arch/riscv/kvm/mmu.c b/arch/riscv/kvm/mmu.c
> new file mode 100644
> index 000000000000..04dd089b86ff
> --- /dev/null
> +++ b/arch/riscv/kvm/mmu.c
> @@ -0,0 +1,83 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (C) 2019 Western Digital Corporation or its affiliates.
> + *
> + * Authors:
> + *     Anup Patel <anup.patel@wdc.com>
> + */
> +
> +#include <linux/bitops.h>
> +#include <linux/errno.h>
> +#include <linux/err.h>
> +#include <linux/hugetlb.h>
> +#include <linux/module.h>
> +#include <linux/uaccess.h>
> +#include <linux/vmalloc.h>
> +#include <linux/kvm_host.h>
> +#include <linux/sched/signal.h>
> +#include <asm/page.h>
> +#include <asm/pgtable.h>
> +
> +void kvm_arch_free_memslot(struct kvm *kvm, struct kvm_memory_slot *free,
> +			   struct kvm_memory_slot *dont)
> +{
> +}
> +
> +int kvm_arch_create_memslot(struct kvm *kvm, struct kvm_memory_slot *slot,
> +			    unsigned long npages)
> +{
> +	return 0;
> +}
> +
> +void kvm_arch_memslots_updated(struct kvm *kvm, u64 gen)
> +{
> +}
> +
> +void kvm_arch_flush_shadow_all(struct kvm *kvm)
> +{
> +	/* TODO: */
> +}
> +
> +void kvm_arch_flush_shadow_memslot(struct kvm *kvm,
> +				   struct kvm_memory_slot *slot)
> +{
> +}
> +
> +void kvm_arch_commit_memory_region(struct kvm *kvm,
> +				const struct kvm_userspace_memory_region *mem,
> +				const struct kvm_memory_slot *old,
> +				const struct kvm_memory_slot *new,
> +				enum kvm_mr_change change)
> +{
> +	/* TODO: */
> +}
> +
> +int kvm_arch_prepare_memory_region(struct kvm *kvm,
> +				struct kvm_memory_slot *memslot,
> +				const struct kvm_userspace_memory_region *mem,
> +				enum kvm_mr_change change)
> +{
> +	/* TODO: */
> +	return 0;
> +}
> +
> +void kvm_riscv_stage2_flush_cache(struct kvm_vcpu *vcpu)
> +{
> +	/* TODO: */
> +}
> +
> +int kvm_riscv_stage2_alloc_pgd(struct kvm *kvm)
> +{
> +	/* TODO: */
> +	return 0;
> +}
> +
> +void kvm_riscv_stage2_free_pgd(struct kvm *kvm)
> +{
> +	/* TODO: */
> +}
> +
> +void kvm_riscv_stage2_update_hgatp(struct kvm_vcpu *vcpu)
> +{
> +	/* TODO: */
> +}
> diff --git a/arch/riscv/kvm/vcpu.c b/arch/riscv/kvm/vcpu.c
> new file mode 100644
> index 000000000000..bd7d6b154f61
> --- /dev/null
> +++ b/arch/riscv/kvm/vcpu.c
> @@ -0,0 +1,316 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (C) 2019 Western Digital Corporation or its affiliates.
> + *
> + * Authors:
> + *     Anup Patel <anup.patel@wdc.com>
> + */
> +
> +#include <linux/bitops.h>
> +#include <linux/errno.h>
> +#include <linux/err.h>
> +#include <linux/kdebug.h>
> +#include <linux/module.h>
> +#include <linux/uaccess.h>
> +#include <linux/vmalloc.h>
> +#include <linux/sched/signal.h>
> +#include <linux/fs.h>
> +#include <linux/kvm_host.h>
> +#include <asm/csr.h>
> +#include <asm/delay.h>
> +#include <asm/hwcap.h>
> +
> +#define VCPU_STAT(x) { #x, offsetof(struct kvm_vcpu, stat.x), KVM_STAT_VCPU }
> +
> +struct kvm_stats_debugfs_item debugfs_entries[] = {
> +	VCPU_STAT(ecall_exit_stat),
> +	VCPU_STAT(wfi_exit_stat),
> +	VCPU_STAT(mmio_exit_user),
> +	VCPU_STAT(mmio_exit_kernel),
> +	VCPU_STAT(exits),
> +	{ NULL }
> +};
> +
> +struct kvm_vcpu *kvm_arch_vcpu_create(struct kvm *kvm, unsigned int id)
> +{
> +	/* TODO: */
> +	return NULL;
> +}
> +
> +int kvm_arch_vcpu_setup(struct kvm_vcpu *vcpu)
> +{
> +	return 0;
> +}
> +
> +void kvm_arch_vcpu_postcreate(struct kvm_vcpu *vcpu)
> +{
> +}
> +
> +int kvm_arch_vcpu_init(struct kvm_vcpu *vcpu)
> +{
> +	/* TODO: */
> +	return 0;
> +}
> +
> +void kvm_arch_vcpu_destroy(struct kvm_vcpu *vcpu)
> +{
> +	/* TODO: */
> +}
> +
> +int kvm_cpu_has_pending_timer(struct kvm_vcpu *vcpu)
> +{
> +	/* TODO: */
> +	return 0;
> +}
> +
> +void kvm_arch_vcpu_blocking(struct kvm_vcpu *vcpu)
> +{
> +}
> +
> +void kvm_arch_vcpu_unblocking(struct kvm_vcpu *vcpu)
> +{
> +}
> +
> +int kvm_arch_vcpu_runnable(struct kvm_vcpu *vcpu)
> +{
> +	/* TODO: */
> +	return 0;
> +}
> +
> +int kvm_arch_vcpu_should_kick(struct kvm_vcpu *vcpu)
> +{
> +	/* TODO: */
> +	return 0;
> +}
> +
> +bool kvm_arch_vcpu_in_kernel(struct kvm_vcpu *vcpu)
> +{
> +	/* TODO: */
> +	return false;
> +}
> +
> +bool kvm_arch_has_vcpu_debugfs(void)
> +{
> +	return false;
> +}
> +
> +int kvm_arch_create_vcpu_debugfs(struct kvm_vcpu *vcpu)
> +{
> +	return 0;
> +}
> +
> +vm_fault_t kvm_arch_vcpu_fault(struct kvm_vcpu *vcpu, struct vm_fault *vmf)
> +{
> +	return VM_FAULT_SIGBUS;
> +}
> +
> +long kvm_arch_vcpu_async_ioctl(struct file *filp,
> +			       unsigned int ioctl, unsigned long arg)
> +{
> +	/* TODO; */
> +	return -ENOIOCTLCMD;
> +}
> +
> +long kvm_arch_vcpu_ioctl(struct file *filp,
> +			 unsigned int ioctl, unsigned long arg)
> +{
> +	/* TODO: */
> +	return -EINVAL;
> +}
> +
> +int kvm_arch_vcpu_ioctl_get_sregs(struct kvm_vcpu *vcpu,
> +				  struct kvm_sregs *sregs)
> +{
> +	return -EINVAL;
> +}
> +
> +int kvm_arch_vcpu_ioctl_set_sregs(struct kvm_vcpu *vcpu,
> +				  struct kvm_sregs *sregs)
> +{
> +	return -EINVAL;
> +}
> +
> +int kvm_arch_vcpu_ioctl_get_fpu(struct kvm_vcpu *vcpu, struct kvm_fpu *fpu)
> +{
> +	return -EINVAL;
> +}
> +
> +int kvm_arch_vcpu_ioctl_set_fpu(struct kvm_vcpu *vcpu, struct kvm_fpu *fpu)
> +{
> +	return -EINVAL;
> +}
> +
> +int kvm_arch_vcpu_ioctl_translate(struct kvm_vcpu *vcpu,
> +				  struct kvm_translation *tr)
> +{
> +	return -EINVAL;
> +}
> +
> +int kvm_arch_vcpu_ioctl_get_regs(struct kvm_vcpu *vcpu, struct kvm_regs *regs)
> +{
> +	return -EINVAL;
> +}
> +
> +int kvm_arch_vcpu_ioctl_set_regs(struct kvm_vcpu *vcpu, struct kvm_regs *regs)
> +{
> +	return -EINVAL;
> +}
> +
> +int kvm_arch_vcpu_ioctl_get_mpstate(struct kvm_vcpu *vcpu,
> +				    struct kvm_mp_state *mp_state)
> +{
> +	/* TODO: */
> +	return 0;
> +}
> +
> +int kvm_arch_vcpu_ioctl_set_mpstate(struct kvm_vcpu *vcpu,
> +				    struct kvm_mp_state *mp_state)
> +{
> +	/* TODO: */
> +	return 0;
> +}
> +
> +int kvm_arch_vcpu_ioctl_set_guest_debug(struct kvm_vcpu *vcpu,
> +					struct kvm_guest_debug *dbg)
> +{
> +	/* TODO; To be implemented later. */
> +	return -EINVAL;
> +}
> +
> +void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
> +{
> +	/* TODO: */
> +
> +	kvm_riscv_stage2_update_hgatp(vcpu);
> +}
> +
> +void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)
> +{
> +	/* TODO: */
> +}
> +
> +static void kvm_riscv_check_vcpu_requests(struct kvm_vcpu *vcpu)
> +{
> +	/* TODO: */
> +}
> +
> +int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *run)
> +{
> +	int ret;
> +	unsigned long scause, stval, htval, htinst;
> +
> +	vcpu->arch.srcu_idx = srcu_read_lock(&vcpu->kvm->srcu);
> +
> +	/* Process MMIO value returned from user-space */
> +	if (run->exit_reason == KVM_EXIT_MMIO) {
> +		ret = kvm_riscv_vcpu_mmio_return(vcpu, vcpu->run);
> +		if (ret) {
> +			srcu_read_unlock(&vcpu->kvm->srcu, vcpu->arch.srcu_idx);
> +			return ret;
> +		}
> +	}
> +
> +	if (run->immediate_exit) {
> +		srcu_read_unlock(&vcpu->kvm->srcu, vcpu->arch.srcu_idx);
> +		return -EINTR;
> +	}
> +
> +	vcpu_load(vcpu);
> +
> +	kvm_sigset_activate(vcpu);
> +
> +	ret = 1;
> +	run->exit_reason = KVM_EXIT_UNKNOWN;
> +	while (ret > 0) {
> +		/* Check conditions before entering the guest */
> +		cond_resched();
> +
> +		kvm_riscv_check_vcpu_requests(vcpu);
> +
> +		preempt_disable();
> +
> +		local_irq_disable();
> +
> +		/*
> +		 * Exit if we have a signal pending so that we can deliver
> +		 * the signal to user space.
> +		 */
> +		if (signal_pending(current)) {
> +			ret = -EINTR;
> +			run->exit_reason = KVM_EXIT_INTR;
> +		}
> +
> +		/*
> +		 * Ensure we set mode to IN_GUEST_MODE after we disable
> +		 * interrupts and before the final VCPU requests check.
> +		 * See the comment in kvm_vcpu_exiting_guest_mode() and
> +		 * Documentation/virtual/kvm/vcpu-requests.rst
> +		 */
> +		vcpu->mode = IN_GUEST_MODE;
> +
> +		srcu_read_unlock(&vcpu->kvm->srcu, vcpu->arch.srcu_idx);
> +		smp_mb__after_srcu_read_unlock();
> +
> +		if (ret <= 0 ||
> +		    kvm_request_pending(vcpu)) {
> +			vcpu->mode = OUTSIDE_GUEST_MODE;
> +			local_irq_enable();
> +			preempt_enable();
> +			vcpu->arch.srcu_idx = srcu_read_lock(&vcpu->kvm->srcu);
> +			continue;
> +		}
> +
> +		guest_enter_irqoff();
> +
> +		__kvm_riscv_switch_to(&vcpu->arch);
> +
> +		vcpu->mode = OUTSIDE_GUEST_MODE;
> +		vcpu->stat.exits++;
> +
> +		/*
> +		 * Save SCAUSE, STVAL, HTVAL, and HTINST because we might
> +		 * get an interrupt between __kvm_riscv_switch_to() and
> +		 * local_irq_enable() which can potentially change CSRs.
> +		 */
> +		scause = csr_read(CSR_SCAUSE);
> +		stval = csr_read(CSR_STVAL);
> +		htval = csr_read(CSR_HTVAL);
> +		htinst = csr_read(CSR_HTINST);
> +
> +		/*
> +		 * We may have taken a host interrupt in VS/VU-mode (i.e.
> +		 * while executing the guest). This interrupt is still
> +		 * pending, as we haven't serviced it yet!
> +		 *
> +		 * We're now back in HS-mode with interrupts disabled
> +		 * so enabling the interrupts now will have the effect
> +		 * of taking the interrupt again, in HS-mode this time.
> +		 */
> +		local_irq_enable();
> +
> +		/*
> +		 * We do local_irq_enable() before calling guest_exit() so
> +		 * that if a timer interrupt hits while running the guest
> +		 * we account that tick as being spent in the guest. We
> +		 * enable preemption after calling guest_exit() so that if
> +		 * we get preempted we make sure ticks after that is not
> +		 * counted as guest time.
> +		 */
> +		guest_exit();
> +
> +		preempt_enable();
> +
> +		vcpu->arch.srcu_idx = srcu_read_lock(&vcpu->kvm->srcu);
> +
> +		ret = kvm_riscv_vcpu_exit(vcpu, run,
> +					  scause, stval, htval, htinst);
> +	}
> +
> +	kvm_sigset_deactivate(vcpu);
> +
> +	vcpu_put(vcpu);
> +
> +	srcu_read_unlock(&vcpu->kvm->srcu, vcpu->arch.srcu_idx);
> +
> +	return ret;
> +}
> diff --git a/arch/riscv/kvm/vcpu_exit.c b/arch/riscv/kvm/vcpu_exit.c
> new file mode 100644
> index 000000000000..dcea9ce4e728
> --- /dev/null
> +++ b/arch/riscv/kvm/vcpu_exit.c
> @@ -0,0 +1,36 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (C) 2019 Western Digital Corporation or its affiliates.
> + *
> + * Authors:
> + *     Anup Patel <anup.patel@wdc.com>
> + */
> +
> +#include <linux/errno.h>
> +#include <linux/err.h>
> +#include <linux/kvm_host.h>
> +
> +/**
> + * kvm_riscv_vcpu_mmio_return -- Handle MMIO loads after user space emulation
> + *			     or in-kernel IO emulation
> + *
> + * @vcpu: The VCPU pointer
> + * @run:  The VCPU run struct containing the mmio data
> + */
> +int kvm_riscv_vcpu_mmio_return(struct kvm_vcpu *vcpu, struct kvm_run *run)
> +{
> +	/* TODO: */
> +	return 0;
> +}
> +
> +/*
> + * Return > 0 to return to guest, < 0 on error, 0 (and set exit_reason) on
> + * proper exit to userspace.
> + */
> +int kvm_riscv_vcpu_exit(struct kvm_vcpu *vcpu, struct kvm_run *run,
> +			unsigned long scause, unsigned long stval,
> +			unsigned long htval, unsigned long htinst)
> +{
> +	/* TODO: */
> +	return 0;
> +}
> diff --git a/arch/riscv/kvm/vm.c b/arch/riscv/kvm/vm.c
> new file mode 100644
> index 000000000000..ac0211820521
> --- /dev/null
> +++ b/arch/riscv/kvm/vm.c
> @@ -0,0 +1,79 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (C) 2019 Western Digital Corporation or its affiliates.
> + *
> + * Authors:
> + *     Anup Patel <anup.patel@wdc.com>
> + */
> +
> +#include <linux/errno.h>
> +#include <linux/err.h>
> +#include <linux/module.h>
> +#include <linux/uaccess.h>
> +#include <linux/kvm_host.h>
> +
> +int kvm_vm_ioctl_get_dirty_log(struct kvm *kvm, struct kvm_dirty_log *log)
> +{
> +	/* TODO: To be added later. */
> +	return -ENOTSUPP;
> +}
> +
> +int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
> +{
> +	int r;
> +
> +	r = kvm_riscv_stage2_alloc_pgd(kvm);
> +	if (r)
> +		return r;
> +
> +	return 0;
> +}
> +
> +void kvm_arch_destroy_vm(struct kvm *kvm)
> +{
> +	int i;
> +
> +	for (i = 0; i < KVM_MAX_VCPUS; ++i) {
> +		if (kvm->vcpus[i]) {
> +			kvm_arch_vcpu_destroy(kvm->vcpus[i]);
> +			kvm->vcpus[i] = NULL;
> +		}
> +	}
> +}
> +
> +int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
> +{
> +	int r;
> +
> +	switch (ext) {
> +	case KVM_CAP_DEVICE_CTRL:
> +	case KVM_CAP_USER_MEMORY:
> +	case KVM_CAP_DESTROY_MEMORY_REGION_WORKS:
> +	case KVM_CAP_ONE_REG:
> +	case KVM_CAP_READONLY_MEM:
> +	case KVM_CAP_MP_STATE:
> +	case KVM_CAP_IMMEDIATE_EXIT:
> +		r = 1;
> +		break;
> +	case KVM_CAP_NR_VCPUS:
> +		r = num_online_cpus();
> +		break;
> +	case KVM_CAP_MAX_VCPUS:
> +		r = KVM_MAX_VCPUS;
> +		break;
> +	case KVM_CAP_NR_MEMSLOTS:
> +		r = KVM_USER_MEM_SLOTS;
> +		break;
> +	default:
> +		r = 0;
> +		break;
> +	}
> +
> +	return r;
> +}
> +
> +long kvm_arch_vm_ioctl(struct file *filp,
> +		       unsigned int ioctl, unsigned long arg)
> +{
> +	return -EINVAL;
> +}
> -- 
> 2.17.1