From mboxrd@z Thu Jan  1 00:00:00 1970
From: Paolo Bonzini <pbonzini@redhat.com>
Subject: Re: [RFC PATCH] kvm-unit-tests : Basic architecture of VMX nested
 test case
Date: Wed, 24 Jul 2013 08:40:34 +0200
Message-ID: <51EF76E2.2030201@redhat.com>
References: <1374087242-6125-1-git-send-email-yzt356@gmail.com> <51E78295.2010700@redhat.com> <20130718072652.GB11772@redhat.com> <51E7C7D2.5040303@redhat.com> <20130718110639.GA26173@redhat.com> <51E7DAD3.8000906@redhat.com> <20130718195712.GN13732@redhat.com> <51E8DFCC.8060108@redhat.com> <20130719094027.GY13732@redhat.com> <51E92BE2.1080600@redhat.com> <CABpY8M+PW8XwPURvOLgLfNE5B-j7JKj-Pin3wFU-3N=OQFOQ-w@mail.gmail.com>
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Cc: Gleb Natapov <gleb@redhat.com>, kvm <kvm@vger.kernel.org>,
	Jan Kiszka <jan.kiszka@web.de>
To: Arthur Chunqi Li <yzt356@gmail.com>
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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.

Paolo

>             SAVE_GPR
>         );
>         eax = exit_handler();
>         switch (eax) {
>         case VMX_TEST_VMEXIT:
>             return 0;
>         case VMX_TEST_RESUME:
>             break;
>         default:
>             printf("%s : unhandled ret from exit_handler.\n", __func__);
>             return 1;
>         }
>         ret = vmresume();
>     }
>     printf("%s : vmenter failed.\n", __func__);
>     return 1;
> }