Re: [PATCH v5 07/17] virt: acrn: Introduce an ioctl to set vCPU registers state

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

On Mon, Oct 19, 2020 at 02:17:53PM +0800, shuo.a.liu@intel.com wrote:
> From: Shuo Liu <shuo.a.liu@intel.com>
> 
> A virtual CPU of User VM has different context due to the different
> registers state. ACRN userspace needs to set the virtual CPU
> registers state (e.g. giving a initial registers state to a virtual
> BSP of a User VM).
> 
> HSM provides an ioctl ACRN_IOCTL_SET_VCPU_REGS to do the virtual CPU
> registers state setting. The ioctl passes the registers state from ACRN
> userspace to the hypervisor directly.
> 
> Signed-off-by: Shuo Liu <shuo.a.liu@intel.com>
> Reviewed-by: Zhi Wang <zhi.a.wang@intel.com>
> Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>
> Cc: Zhi Wang <zhi.a.wang@intel.com>
> Cc: Zhenyu Wang <zhenyuw@linux.intel.com>
> Cc: Yu Wang <yu1.wang@intel.com>
> Cc: Reinette Chatre <reinette.chatre@intel.com>
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> ---
>  drivers/virt/acrn/hsm.c       | 15 ++++++++
>  drivers/virt/acrn/hypercall.h | 13 +++++++
>  include/uapi/linux/acrn.h     | 71 +++++++++++++++++++++++++++++++++++
>  3 files changed, 99 insertions(+)
> 
> diff --git a/drivers/virt/acrn/hsm.c b/drivers/virt/acrn/hsm.c
> index cbda67d4eb89..58ceb02e82db 100644
> --- a/drivers/virt/acrn/hsm.c
> +++ b/drivers/virt/acrn/hsm.c
> @@ -9,6 +9,7 @@
>   *	Yakui Zhao <yakui.zhao@intel.com>
>   */
>  
> +#include <linux/io.h>
>  #include <linux/mm.h>
>  #include <linux/module.h>
>  #include <linux/slab.h>
> @@ -46,6 +47,7 @@ static long acrn_dev_ioctl(struct file *filp, unsigned int cmd,
>  {
>  	struct acrn_vm *vm = filp->private_data;
>  	struct acrn_vm_creation *vm_param;
> +	struct acrn_vcpu_regs *cpu_regs;
>  	int ret = 0;
>  
>  	if (vm->vmid == ACRN_INVALID_VMID && cmd != ACRN_IOCTL_CREATE_VM) {
> @@ -97,6 +99,19 @@ static long acrn_dev_ioctl(struct file *filp, unsigned int cmd,
>  	case ACRN_IOCTL_DESTROY_VM:
>  		ret = acrn_vm_destroy(vm);
>  		break;
> +	case ACRN_IOCTL_SET_VCPU_REGS:
> +		cpu_regs = memdup_user((void __user *)ioctl_param,
> +				       sizeof(struct acrn_vcpu_regs));
> +		if (IS_ERR(cpu_regs))
> +			return PTR_ERR(cpu_regs);
> +
> +		ret = hcall_set_vcpu_regs(vm->vmid, virt_to_phys(cpu_regs));

Why the virt_to_phys() call here?  And there really is no validation of
any fields?

> +		if (ret < 0)
> +			dev_dbg(acrn_dev.this_device,

Wait, a global, static device?  Where did I miss that?  That feels odd,
why is there just one?



> +				"Failed to set regs state of VM%u!\n",
> +				vm->vmid);
> +		kfree(cpu_regs);
> +		break;
>  	default:
>  		dev_dbg(acrn_dev.this_device, "Unknown IOCTL 0x%x!\n", cmd);
>  		ret = -ENOTTY;
> diff --git a/drivers/virt/acrn/hypercall.h b/drivers/virt/acrn/hypercall.h
> index 426b66cadb1f..f29cfae08862 100644
> --- a/drivers/virt/acrn/hypercall.h
> +++ b/drivers/virt/acrn/hypercall.h
> @@ -19,6 +19,7 @@
>  #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)
> +#define HC_SET_VCPU_REGS		_HC_ID(HC_ID, HC_ID_VM_BASE + 0x06)
>  
>  /**
>   * hcall_create_vm() - Create a User VM
> @@ -75,4 +76,16 @@ static inline long hcall_reset_vm(u64 vmid)
>  	return acrn_hypercall1(HC_RESET_VM, vmid);
>  }
>  
> +/**
> + * hcall_set_vcpu_regs() - Set up registers of virtual CPU of a User VM
> + * @vmid:	User VM ID
> + * @regs_state:	Service VM GPA of registers state
> + *
> + * Return: 0 on success, <0 on failure
> + */
> +static inline long hcall_set_vcpu_regs(u64 vmid, u64 regs_state)
> +{
> +	return acrn_hypercall2(HC_SET_VCPU_REGS, vmid, regs_state);
> +}
> +
>  #endif /* __ACRN_HSM_HYPERCALL_H */
> diff --git a/include/uapi/linux/acrn.h b/include/uapi/linux/acrn.h
> index 364b1a783074..1d5b82e154fb 100644
> --- a/include/uapi/linux/acrn.h
> +++ b/include/uapi/linux/acrn.h
> @@ -36,6 +36,75 @@ struct acrn_vm_creation {
>  	__u8	reserved2[8];
>  } __attribute__((aligned(8)));
>  
> +struct acrn_gp_regs {
> +	__u64	rax;
> +	__u64	rcx;
> +	__u64	rdx;
> +	__u64	rbx;
> +	__u64	rsp;
> +	__u64	rbp;
> +	__u64	rsi;
> +	__u64	rdi;
> +	__u64	r8;
> +	__u64	r9;
> +	__u64	r10;
> +	__u64	r11;
> +	__u64	r12;
> +	__u64	r13;
> +	__u64	r14;
> +	__u64	r15;
> +};
> +
> +struct acrn_descriptor_ptr {
> +	__u16	limit;
> +	__u64	base;
> +	__u16	reserved[3];
> +} __attribute__ ((__packed__));
> +
> +struct acrn_regs {
> +	struct acrn_gp_regs		gprs;
> +	struct acrn_descriptor_ptr	gdt;
> +	struct acrn_descriptor_ptr	idt;
> +
> +	__u64				rip;

As these are all crossing the user/kernel boundry and then on to
somewhere "else", you have to specify the endian of all of these, right?

if not, why not?



> +	__u64				cs_base;
> +	__u64				cr0;
> +	__u64				cr4;
> +	__u64				cr3;
> +	__u64				ia32_efer;
> +	__u64				rflags;
> +	__u64				reserved_64[4];
> +
> +	__u32				cs_ar;
> +	__u32				cs_limit;
> +	__u32				reserved_32[3];
> +
> +	__u16				cs_sel;
> +	__u16				ss_sel;
> +	__u16				ds_sel;
> +	__u16				es_sel;
> +	__u16				fs_sel;
> +	__u16				gs_sel;
> +	__u16				ldt_sel;
> +	__u16				tr_sel;
> +
> +	__u16				reserved_16[4];
> +};
> +
> +/**
> + * struct acrn_vcpu_regs - Info of vCPU registers state
> + * @vcpu_id:	vCPU ID
> + * @reserved0:	Reserved
> + * @vcpu_regs:	vCPU registers state
> + *
> + * This structure will be passed to hypervisor directly.
> + */
> +struct acrn_vcpu_regs {
> +	__u16			vcpu_id;

Endian?

> +	__u16			reserved0[3];

What does the reserved fields do?

Is there a pointer to a public document for all of these structures
somewhere?

> +	struct acrn_regs	vcpu_regs;
> +} __attribute__((aligned(8)));

What does the alignment do here?

thanks,

greg k-h