Re: [RFC PATCH] kvm-unit-tests : Basic architecture of VMX nested test case

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So as what Gleb said, what about the following codes:

static int vmx_run2()
{
    u32 eax;
    bool ret;

    asm volatile(
        "mov %%rsp, %%rsi\n\t"
        "mov %2, %%edi\n\t"
        "call vmcs_write\n\t"
        "vmlaunch\n\t"
        "setbe %0\n\t"
        "jne 4f\n\t"

        "vmx_return:\n\t"
        SAVE_GPR_C
        "call exit_handler\n\t"
        "cmp %3, %%eax\n\t"
        "je 2f\n\t"
        "cmp %4, %%eax\n\t"
        "je 1f\n\t"
        "jmp 3f\n\t"

        /* VMX_TEST_RESUME */
        "1:\n\t"
        LOAD_GPR_C
        "vmresume\n\t"
        "setbe %0\n\t"
        "jne 4f\n\t"
        /* VMX_TEST_VMEXIT */
        "2:\n\t"
        "mov $0, %1\n\t"
        "jmp 5f\n\t"
        /* undefined ret from exit_handler */
        "3:\n\t"
        "mov $2, %1\n\t"
        "jmp 5f\n\t"
        /* vmlaunch/vmresume failed, exit */
        "4:\n\t"
        "mov $1, %1\n\t"
        "5:\n\t"
        : "=r"(ret), "=r"(eax)
        : "i"(HOST_RSP), "i"(VMX_TEST_VMEXIT),
          "i"(VMX_TEST_RESUME)
        : "rax", "rbx", "rdi", "rsi",
           "r8", "r9", "r10", "r11", "r12", "r13", "r14", "r15",
          "memory", "cc"
    );
    switch (eax) {
    case 0:
        return 0;
    case 1:
        printf("%s : vmenter failed.\n", __func__);
        break;
    default:
        printf("%s : unhandled ret from exit_handler.\n", __func__);
        break;
    }
    return 1;
}

On Wed, Jul 24, 2013 at 2:48 PM, Paolo Bonzini <pbonzini@xxxxxxxxxx> wrote:
> Il 24/07/2013 08:46, Arthur Chunqi Li ha scritto:
>> On Wed, Jul 24, 2013 at 2:40 PM, Paolo Bonzini <pbonzini@xxxxxxxxxx> wrote:
>>> Il 24/07/2013 08:11, Arthur Chunqi Li ha scritto:
>>>>
>>>> static int vmx_run()
>>>> {
>>>>     u32 eax;
>>>>     bool ret;
>>>>
>>>>     vmcs_write(HOST_RSP, get_rsp());
>>>>     ret = vmlaunch();
>>>
>>> The compiler can still change rsp between here...
>>>
>>>>     while (!ret) {
>>>>         asm volatile(
>>>>             "vmx_return:\n\t"
>>>
>>> ... and here.
>>>
>>> If you want to write it in C, the only thing that can be after
>>> vmlaunch/vmresume is "exit()".  Else it has to be asm.
>> Actually, you mean we need to write all the codes in asm to avoid
>> changing to rsp, right?
>
> Not necessarily all the code.  It is also ok to use setjmp/longjmp with
> a small asm trampoline, because this method won't care about the exact
> rsp values that are used.  But if you want to do as Gleb said, and put
> vmx_return just after vmlaunch, it has to be all asm as in KVM's
> arch/x86/kvm/vmx.c.
>
> Paolo



-- 
Arthur Chunqi Li
Department of Computer Science
School of EECS
Peking University
Beijing, China
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