From mboxrd@z Thu Jan  1 00:00:00 1970
From: Avi Kivity <avi@redhat.com>
Subject: Re: problem wit svm_get_msr on kvm-kmod-2.6.31.6
Date: Mon, 16 Nov 2009 14:01:46 +0200
Message-ID: <4B013F2A.2040900@redhat.com>
References: <90D306BE6EBC8D428A824FBBA7A3113D014275E0F0@ronja.maurer-it.com> <4B012709.20508@redhat.com> <90D306BE6EBC8D428A824FBBA7A3113D014275E0F2@ronja.maurer-it.com> <4B012EDF.7030109@redhat.com> <90D306BE6EBC8D428A824FBBA7A3113D014275E0F5@ronja.maurer-it.com>
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Cc: kvm <kvm@vger.kernel.org>
To: Dietmar Maurer <dietmar@proxmox.com>,
	Jan Kiszka <jan.kiszka@siemens.com>
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On 11/16/2009 01:17 PM, Dietmar Maurer wrote:
>      38f0:       0f 85 82 01 00 00       jne    3a78<svm_get_msr+0x2b8>
>      38f6:       48 8b 87 e0 27 00 00    mov    0x27e0(%rdi),%rax
>      38fd:       48 8b 48 50             mov    0x50(%rax),%rcx
>      3901:       0f 31                   rdtsc
>      3903:       48 01 c8                add    %rcx,%rax
>
> # this is svm_get_msr+0x146
>      3906:       48 89 02                mov    %rax,(%rdx)
>    


Looks like a miscompile of native_read_tsc(), it needs to use %edx:%eax, 
not assume the result is in %rax.

Jan, looks like the culprit is

   static inline unsigned long long kvm_native_read_tsc(void)
   {
         unsigned long long val;
         asm volatile("rdtsc" : "=A" (val));
         return val;
   }

"=A" only works correctly on i386, need to use "=a" "=d" for portability.

-- 
error compiling committee.c: too many arguments to function