Date:   Thu, 10 Sep 2020 14:19:00 +0800
From:   Shuo A Liu <shuo.a.liu@...el.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     linux-kernel@...r.kernel.org, x86@...nel.org,
        "H . Peter Anvin" <hpa@...or.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Yu Wang <yu1.wang@...el.com>,
        Reinette Chatre <reinette.chatre@...el.com>,
        Zhi Wang <zhi.a.wang@...el.com>,
        Zhenyu Wang <zhenyuw@...ux.intel.com>
Subject: Re: [PATCH v3 06/17] virt: acrn: Introduce VM management interfaces

Hi Greg,

On Wed  9.Sep'20 at 11:45:16 +0200, Greg Kroah-Hartman wrote:
>On Wed, Sep 09, 2020 at 05:08:25PM +0800, shuo.a.liu@...el.com wrote:
>> From: Shuo Liu <shuo.a.liu@...el.com>
>>
>> The VM management interfaces expose several VM operations to ACRN
>> userspace via ioctls. For example, creating VM, starting VM, destroying
>> VM and so on.
>>
>> The ACRN Hypervisor needs to exchange data with the ACRN userspace
>> during the VM operations. HSM provides VM operation ioctls to the ACRN
>> userspace and communicates with the ACRN Hypervisor for VM operations
>> via hypercalls.
>>
>> HSM maintains a list of User VM. Each User VM will be bound to an
>> existing file descriptor of /dev/acrn_hsm. The User VM will be
>> destroyed when the file descriptor is closed.
>>
>> Signed-off-by: Shuo Liu <shuo.a.liu@...el.com>
>> Reviewed-by: Zhi Wang <zhi.a.wang@...el.com>
>> Reviewed-by: Reinette Chatre <reinette.chatre@...el.com>
>> Cc: Zhi Wang <zhi.a.wang@...el.com>
>> Cc: Zhenyu Wang <zhenyuw@...ux.intel.com>
>> Cc: Yu Wang <yu1.wang@...el.com>
>> Cc: Reinette Chatre <reinette.chatre@...el.com>
>> Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
>> ---
>>  .../userspace-api/ioctl/ioctl-number.rst      |  1 +
>>  MAINTAINERS                                   |  1 +
>>  drivers/virt/acrn/Makefile                    |  2 +-
>>  drivers/virt/acrn/acrn_drv.h                  | 22 +++++-
>>  drivers/virt/acrn/hsm.c                       | 66 ++++++++++++++++
>>  drivers/virt/acrn/hypercall.h                 | 78 +++++++++++++++++++
>>  drivers/virt/acrn/vm.c                        | 69 ++++++++++++++++
>>  include/uapi/linux/acrn.h                     | 56 +++++++++++++
>>  8 files changed, 293 insertions(+), 2 deletions(-)
>>  create mode 100644 drivers/virt/acrn/hypercall.h
>>  create mode 100644 drivers/virt/acrn/vm.c
>>  create mode 100644 include/uapi/linux/acrn.h
>>
>> diff --git a/Documentation/userspace-api/ioctl/ioctl-number.rst b/Documentation/userspace-api/ioctl/ioctl-number.rst
>> index 2a198838fca9..ac60efedb104 100644
>> --- a/Documentation/userspace-api/ioctl/ioctl-number.rst
>> +++ b/Documentation/userspace-api/ioctl/ioctl-number.rst
>> @@ -319,6 +319,7 @@ Code  Seq#    Include File                                           Comments
>>  0xA0  all    linux/sdp/sdp.h                                         Industrial Device Project
>>                                                                       <mailto:kenji@...gate.com>
>>  0xA1  0      linux/vtpm_proxy.h                                      TPM Emulator Proxy Driver
>> +0xA2  all    uapi/linux/acrn.h                                       ACRN hypervisor
>>  0xA3  80-8F                                                          Port ACL  in development:
>>                                                                       <mailto:tlewis@...dspring.com>
>>  0xA3  90-9F  linux/dtlk.h
>> diff --git a/MAINTAINERS b/MAINTAINERS
>> index 3030d0e93d02..d4c1ef303c2d 100644
>> --- a/MAINTAINERS
>> +++ b/MAINTAINERS
>> @@ -443,6 +443,7 @@ S:	Supported
>>  W:	https://projectacrn.org
>>  F:	Documentation/virt/acrn/
>>  F:	drivers/virt/acrn/
>> +F:	include/uapi/linux/acrn.h
>>
>>  AD1889 ALSA SOUND DRIVER
>>  L:	linux-parisc@...r.kernel.org
>> diff --git a/drivers/virt/acrn/Makefile b/drivers/virt/acrn/Makefile
>> index 6920ed798aaf..cf8b4ed5e74e 100644
>> --- a/drivers/virt/acrn/Makefile
>> +++ b/drivers/virt/acrn/Makefile
>> @@ -1,3 +1,3 @@
>>  # SPDX-License-Identifier: GPL-2.0
>>  obj-$(CONFIG_ACRN_HSM)	:= acrn.o
>> -acrn-y := hsm.o
>> +acrn-y := hsm.o vm.o
>> diff --git a/drivers/virt/acrn/acrn_drv.h b/drivers/virt/acrn/acrn_drv.h
>> index 29eedd696327..043ae6840995 100644
>> --- a/drivers/virt/acrn/acrn_drv.h
>> +++ b/drivers/virt/acrn/acrn_drv.h
>> @@ -3,16 +3,36 @@
>>  #ifndef __ACRN_HSM_DRV_H
>>  #define __ACRN_HSM_DRV_H
>>
>> +#include <linux/acrn.h>
>> +#include <linux/dev_printk.h>
>>  #include <linux/types.h>
>>
>> +#include "hypercall.h"
>> +
>>  #define ACRN_INVALID_VMID (0xffffU)
>>
>> +#define ACRN_VM_FLAG_DESTROYED		0U
>> +extern struct list_head acrn_vm_list;
>> +extern rwlock_t acrn_vm_list_lock;
>>  /**
>>   * struct acrn_vm - Properties of ACRN User VM.
>> + * @dev:	The struct device this VM belongs to
>> + * @list:	Entry within global list of all VMs
>>   * @vmid:	User VM ID
>> + * @vcpu_num:	Number of virtual CPUs in the VM
>> + * @flags:	Flags (ACRN_VM_FLAG_*) of the VM. This is VM flag management
>> + *		in HSM which is different from the &acrn_vm_creation.vm_flag.
>>   */
>>  struct acrn_vm {
>> -	u16	vmid;
>> +	struct device		*dev;
>> +	struct list_head	list;
>> +	u16			vmid;
>> +	int			vcpu_num;
>> +	unsigned long		flags;
>>  };
>>
>> +struct acrn_vm *acrn_vm_create(struct acrn_vm *vm,
>> +			       struct acrn_vm_creation *vm_param);
>> +int acrn_vm_destroy(struct acrn_vm *vm);
>> +
>>  #endif /* __ACRN_HSM_DRV_H */
>> diff --git a/drivers/virt/acrn/hsm.c b/drivers/virt/acrn/hsm.c
>> index 28a3052ffa55..bc85a3c14f87 100644
>> --- a/drivers/virt/acrn/hsm.c
>> +++ b/drivers/virt/acrn/hsm.c
>> @@ -19,6 +19,8 @@
>>
>>  #include "acrn_drv.h"
>>
>> +static struct miscdevice acrn_dev;
>> +
>>  /*
>>   * When /dev/acrn_hsm is opened, a 'struct acrn_vm' object is created to
>>   * represent a VM instance and continues to be associated with the opened file
>> @@ -34,14 +36,77 @@ static int acrn_dev_open(struct inode *inode, struct file *filp)
>>  		return -ENOMEM;
>>
>>  	vm->vmid = ACRN_INVALID_VMID;
>> +	vm->dev = get_device(acrn_dev.this_device);
>
>You are grabbing a reference on a static structure?

acrn_dev is static, but acrn_dev.this_device is not.

>
>Ugh, who reviewed this code before it was sent out???

This part was just newly added according to your suggestion.. Please
refer to
https://lore.kernel.org/lkml/1946bf48-fda7-20e0-246d-93414a1a67f5@intel.com/

>
>Think about what you just asked for here, and if that actually makes any
>sense at all...
>
>>  	filp->private_data = vm;
>>  	return 0;
>>  }
>>
>> +static long acrn_dev_ioctl(struct file *filp, unsigned int cmd,
>> +			   unsigned long ioctl_param)
>> +{
>> +	struct acrn_vm *vm = filp->private_data;
>> +	struct acrn_vm_creation *vm_param;
>> +	int ret = 0;
>> +
>> +	if (vm->vmid == ACRN_INVALID_VMID && cmd != ACRN_IOCTL_CREATE_VM) {
>> +		dev_err(vm->dev, "ioctl 0x%x: Invalid VM state!\n", cmd);
>> +		return -EFAULT;
>
>You did not just cause a memory fault, so please do not return that
>error to userspace, it will just get confused.

Will change to -EINVAL.

>
>And does this allow userspace to spam the kernel log with errors by
>calling this ioctl with invalid commands?  If so, make this a debugging
>message please.

OK. It will be dev_dbg().

>
>> +	}
>> +
>> +	switch (cmd) {
>> +	case ACRN_IOCTL_CREATE_VM:
>> +		vm_param = memdup_user((void __user *)ioctl_param,
>> +				       sizeof(struct acrn_vm_creation));
>> +		if (IS_ERR(vm_param))
>> +			return PTR_ERR(vm_param);
>> +
>> +		vm = acrn_vm_create(vm, vm_param);
>> +		if (!vm) {
>> +			ret = -EFAULT;
>
>Again, this is not a fault, fix all of these up please.

Sure. I will change them to -EINVAL.

>
>And you really are doing the validation of the parameters in the
>hypervisor itself? You should add a comment here explicitly saying you
>are trusting that layer to do this, as it will come up in the future
>once bugs start being reported :)

Yes, the hypervisor has. I will mention it somewhere. Maybe comments
before acrn_dev_ioctl().

>
>> +			kfree(vm_param);
>> +			break;
>> +		}
>> +
>> +		if (copy_to_user((void __user *)ioctl_param, vm_param,
>> +				 sizeof(struct acrn_vm_creation))) {
>> +			acrn_vm_destroy(vm);
>> +			ret = -EFAULT;
>
>That's a correct error :)
>
>> +		}
>> +
>> +		kfree(vm_param);
>> +		break;
>> +	case ACRN_IOCTL_START_VM:
>> +		ret = hcall_start_vm(vm->vmid);
>> +		if (ret < 0)
>> +			dev_err(vm->dev, "Failed to start VM %u!\n", vm->vmid);
>> +		break;
>> +	case ACRN_IOCTL_PAUSE_VM:
>> +		ret = hcall_pause_vm(vm->vmid);
>> +		if (ret < 0)
>> +			dev_err(vm->dev, "Failed to pause VM %u!\n", vm->vmid);
>> +		break;
>> +	case ACRN_IOCTL_RESET_VM:
>> +		ret = hcall_reset_vm(vm->vmid);
>> +		if (ret < 0)
>> +			dev_err(vm->dev, "Failed to restart VM %u!\n", vm->vmid);
>> +		break;
>> +	case ACRN_IOCTL_DESTROY_VM:
>> +		ret = acrn_vm_destroy(vm);
>> +		break;
>> +	default:
>> +		dev_warn(vm->dev, "Unknown IOCTL 0x%x!\n", cmd);
>> +		ret = -ENOTTY;
>> +	}
>> +
>> +	return ret;
>> +}
>> +
>>  static int acrn_dev_release(struct inode *inode, struct file *filp)
>>  {
>>  	struct acrn_vm *vm = filp->private_data;
>>
>> +	acrn_vm_destroy(vm);
>> +	put_device(vm->dev);
>>  	kfree(vm);
>>  	return 0;
>>  }
>> @@ -50,6 +115,7 @@ static const struct file_operations acrn_fops = {
>>  	.owner		= THIS_MODULE,
>>  	.open		= acrn_dev_open,
>>  	.release	= acrn_dev_release,
>> +	.unlocked_ioctl = acrn_dev_ioctl,
>>  };
>>
>>  static struct miscdevice acrn_dev = {
>> diff --git a/drivers/virt/acrn/hypercall.h b/drivers/virt/acrn/hypercall.h
>> new file mode 100644
>> index 000000000000..426b66cadb1f
>> --- /dev/null
>> +++ b/drivers/virt/acrn/hypercall.h
>> @@ -0,0 +1,78 @@
>> +/* SPDX-License-Identifier: GPL-2.0 */
>> +/*
>> + * ACRN HSM: hypercalls of ACRN Hypervisor
>> + */
>> +#ifndef __ACRN_HSM_HYPERCALL_H
>> +#define __ACRN_HSM_HYPERCALL_H
>> +#include <asm/acrn.h>
>> +
>> +/*
>> + * Hypercall IDs of the ACRN Hypervisor
>> + */
>> +#define _HC_ID(x, y) (((x) << 24) | (y))
>> +
>> +#define HC_ID 0x80UL
>> +
>> +#define HC_ID_VM_BASE			0x10UL
>> +#define HC_CREATE_VM			_HC_ID(HC_ID, HC_ID_VM_BASE + 0x00)
>> +#define HC_DESTROY_VM			_HC_ID(HC_ID, HC_ID_VM_BASE + 0x01)
>> +#define HC_START_VM			_HC_ID(HC_ID, HC_ID_VM_BASE + 0x02)
>> +#define HC_PAUSE_VM			_HC_ID(HC_ID, HC_ID_VM_BASE + 0x03)
>> +#define HC_RESET_VM			_HC_ID(HC_ID, HC_ID_VM_BASE + 0x05)
>> +
>> +/**
>> + * hcall_create_vm() - Create a User VM
>> + * @vminfo:	Service VM GPA of info of User VM creation
>> + *
>> + * Return: 0 on success, <0 on failure
>> + */
>> +static inline long hcall_create_vm(u64 vminfo)
>> +{
>> +	return acrn_hypercall1(HC_CREATE_VM, vminfo);
>> +}
>> +
>> +/**
>> + * hcall_start_vm() - Start a User VM
>> + * @vmid:	User VM ID
>> + *
>> + * Return: 0 on success, <0 on failure
>> + */
>> +static inline long hcall_start_vm(u64 vmid)
>> +{
>> +	return acrn_hypercall1(HC_START_VM, vmid);
>> +}
>> +
>> +/**
>> + * hcall_pause_vm() - Pause a User VM
>> + * @vmid:	User VM ID
>> + *
>> + * Return: 0 on success, <0 on failure
>> + */
>> +static inline long hcall_pause_vm(u64 vmid)
>> +{
>> +	return acrn_hypercall1(HC_PAUSE_VM, vmid);
>> +}
>> +
>> +/**
>> + * hcall_destroy_vm() - Destroy a User VM
>> + * @vmid:	User VM ID
>> + *
>> + * Return: 0 on success, <0 on failure
>> + */
>> +static inline long hcall_destroy_vm(u64 vmid)
>> +{
>> +	return acrn_hypercall1(HC_DESTROY_VM, vmid);
>> +}
>> +
>> +/**
>> + * hcall_reset_vm() - Reset a User VM
>> + * @vmid:	User VM ID
>> + *
>> + * Return: 0 on success, <0 on failure
>> + */
>> +static inline long hcall_reset_vm(u64 vmid)
>> +{
>> +	return acrn_hypercall1(HC_RESET_VM, vmid);
>> +}
>> +
>> +#endif /* __ACRN_HSM_HYPERCALL_H */
>> diff --git a/drivers/virt/acrn/vm.c b/drivers/virt/acrn/vm.c
>> new file mode 100644
>> index 000000000000..851a9481a78e
>> --- /dev/null
>> +++ b/drivers/virt/acrn/vm.c
>> @@ -0,0 +1,69 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +/*
>> + * ACRN_HSM: Virtual Machine management
>> + *
>> + * Copyright (C) 2020 Intel Corporation. All rights reserved.
>> + *
>> + * Authors:
>> + *	Jason Chen CJ <jason.cj.chen@...el.com>
>> + *	Yakui Zhao <yakui.zhao@...el.com>
>> + */
>> +#include <linux/io.h>
>> +#include <linux/mm.h>
>> +#include <linux/slab.h>
>> +
>> +#include "acrn_drv.h"
>> +
>> +/* List of VMs */
>> +LIST_HEAD(acrn_vm_list);
>> +/*
>> + * acrn_vm_list is read in a tasklet which dispatch I/O requests and is wrote
>> + * in VM creation ioctl. Use the rwlock mechanism to protect it.
>> + */
>> +DEFINE_RWLOCK(acrn_vm_list_lock);
>> +
>> +struct acrn_vm *acrn_vm_create(struct acrn_vm *vm,
>> +			       struct acrn_vm_creation *vm_param)
>> +{
>> +	int ret;
>> +
>> +	ret = hcall_create_vm(virt_to_phys(vm_param));
>> +	if (ret < 0 || vm_param->vmid == ACRN_INVALID_VMID) {
>> +		dev_err(vm->dev, "Failed to create VM! Error: %d\n", ret);
>> +		return NULL;
>> +	}
>> +
>> +	vm->vmid = vm_param->vmid;
>> +	vm->vcpu_num = vm_param->vcpu_num;
>> +
>> +	write_lock_bh(&acrn_vm_list_lock);
>> +	list_add(&vm->list, &acrn_vm_list);
>
>Wait, why do you have a global list of devices?  Shouldn't that device
>be tied to the vm structure?  Who will be iterating this list that does
>not have the file handle to start with?

Active VMs in this list will be used by the I/O requests dispatching
tasklet ioreq_tasklet, whose callback function is ioreq_tasklet_handler()
in patch 0009. ioreq_tasklet_handler() currently handles the notification
interrupt from the hypervisor and dispatches I/O requests to each VMs.

So, the VM list is iterated in a tasklet and be protected by a rwlock.
The device tied to vm structure is just for log API dev_*() now.

>
>
>
>> +	write_unlock_bh(&acrn_vm_list_lock);
>> +
>> +	dev_dbg(vm->dev, "VM %u created.\n", vm->vmid);
>> +	return vm;
>> +}
>> +
>> +int acrn_vm_destroy(struct acrn_vm *vm)
>> +{
>> +	int ret;
>> +
>> +	if (vm->vmid == ACRN_INVALID_VMID ||
>> +	    test_and_set_bit(ACRN_VM_FLAG_DESTROYED, &vm->flags))
>> +		return 0;
>> +
>> +	/* Remove from global VM list */
>> +	write_lock_bh(&acrn_vm_list_lock);
>> +	list_del_init(&vm->list);
>> +	write_unlock_bh(&acrn_vm_list_lock);
>
>Again, why this list at all?

Please refer to the previous comments.

Thanks
shuo

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