Il 17/07/2013 15:48, Arthur Chunqi Li ha scritto:
> Actually, both structure are kind to me and except for some concerns
> Gleb's solutions seems easier to read.
>
> The first concern is Gleb's way cannot set a seperate stack for
> HOST_RSP, which I predefined this can be set by test suite's init
> function. I have discussed with Jan and he said we don't have such
> test cases.
>
> The second is huge function and more assembler codes, I will separate
> vmx_handler codes and this is not important.
>
> I have another question, I write codes like this:
>
> asm volatile("vmlaunch;seta %0\n\t" : "=m"(ret));
Note that this asm needs a "memory" clobber too. This is what I
referred to as "more complications in where to put compiler barriers" in
my earlier message. In general, bypassing compiler optimizations is why
I preferred your earlier solution.
> /* Should not reach here */
> printf("%s : vmlaunch failed, ret=%d.\n", __func__, ret);
> goto err;
>
> while(1) {
> ....
> }
>
> Then because we use -O1 optimization param for our test cases, all the
> codes after "goto" are gone and I got the following error:
>
> /root/xelatex.kvm-unit-tests-vmx.git/x86/vmx.c:247: undefined
> reference to `vmx_return'
> collect2: ld returned 1 exit status
>
> So how could I disable the opt for this function or bypass such occasion?
You can do something like
ret = 0;
asm volatile("vmlaunch;seta %0\n\t" : "=m"(ret) : : "memory");
/* Actually we go straight to the while(1) below if ret==0 */
if (ret) {
printf("%s : vmlaunch failed, ret=%d.\n", __func__, ret);
goto err;
}
while(1) {
...
}
or if you want to make it more explicit to the compiler:
ret = 0;
/* asm goto cannot have outputs :( */
asm volatile goto ("vmlaunch;seta (%0)\n\t" : : "r"(&ret)
: "memory" : resume);
printf("%s : vmlaunch failed, ret=%d.\n", __func__, ret);
goto err;
resume:
while(1) {
...
}
Paolo
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