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 <pbonz...@redhat.com> wrote:
> Il 24/07/2013 08:46, Arthur Chunqi Li ha scritto:
>> On Wed, Jul 24, 2013 at 2:40 PM, Paolo Bonzini <pbonz...@redhat.com> 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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