Re: [Xen-devel] [PATCH v3 07/32] xen/x86: fix arch_set_info_guest for HVM guests

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

El 24/07/15 a les 10.22, Jan Beulich ha escrit:
>>>> On 23.07.15 at 19:12, <andrew.cooper3@xxxxxxxxxx> wrote:
>> I would go with Jan's suggestion and make
>> XEN_DOMCTL_{get/set}vcpucontext ineligible for use on HVM guests.
> 
> Plus, as you said earlier, a new VCPUOP_initialize.

(Adding the Linux maintainers to get their opinion on the interface)

Just to recap and to make sure I got all the points:

 - vCPU initialization from the toolstack (BSP initialization) is going 
to be done using XEN_DOMCTL_sethvmcontext.
 - XEN_DOMCTL_{get/set}vcpucontext is going to return EOPNOTSUPP for 
HVM guests.
 - A new vcpu_guest_contatext (vcpu_hvm_context?) is going to be 
introduced together with a a new VCPUOP_initialize hypercall 
(VCPUOP_hvm_initialize?).

The following is a layout proposal for the new vcpu_context:

struct vcpu_hvm_context {
/* 32bit fields of the structure will be used. */
#define _VCPUHVM_MODE_32B              0
#define VCPUHVM_MODE_32B               (1<<_VCPUHVM_MODE_32B)
/* 64bit fields of the structure will be used. */
#define _VCPUHVM_MODE_64B              1
#define VCPUHVM_MODE_64B               (1<<_VCPUHVM_MODE_64B)
#define _VCPUHVM_online                2
#define VCPUHVM_online                 (1<<_VCPUHVM_online )
    uint32_t flags;                         /* VCPUHVM_* flags.   */
    struct cpu_hvm_regs user_regs;          /* CPU registers.     */
};

#if defined(__GNUC__) && !defined(__STRICT_ANSI__)
/* Anonymous union includes both 32- and 64-bit names (e.g., ebp/rbp). */
# define __DECL_REG(n64, n32) union {          \
        uint64_t n64;                          \
        uint32_t n32;                          \
    }
#else
/* Non-gcc sources must always use the proper 64-bit name (e.g., rbp). */
#define __DECL_REG(n64, n32) uint64_t n64
#endif

#define __DECL_GP_REG(n) __DECL_REG(r##n, e##n)

struct cpu_hvm_regs {
    /* General purpose registers. */
    __DECL_GP_REG(bx);
    __DECL_GP_REG(cx);
    __DECL_GP_REG(dx);
    __DECL_GP_REG(si);
    __DECL_GP_REG(di);
    __DECL_GP_REG(bp);
    __DECL_GP_REG(ax);
    __DECL_GP_REG(ip);
    __DECL_GP_REG(sp);
    __DECL_GP_REG(flags);

    /* Control registers.         */
    uint64_t cr[8];
    /* Valid on amd64 only.       */
    uint64_t efer;

    /* Debug registers.           */
    uint64_t db[8];  
};

#undef __DECL_GP_REG
#undef __DECL_REG

Of course the APs will be allowed to start in any mode they wish, 
regardless of the mode the guest is currently running on.

Roger.

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