From mboxrd@z Thu Jan  1 00:00:00 1970
From: Samuel Thibault <samuel.thibault@eu.citrix.com>
Subject: FPU exception
Date: Tue, 4 Mar 2008 12:10:50 +0000
Message-ID: <20080304121050.GA8880@implementation.uk.xensource.com>
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Hello,

I was trying to boot w98 when I got a BUG:

(XEN) Xen BUG at traps.c:2640                                                   
(XEN) ----[ Xen-3.3-unstable  x86_64  debug=n  Not tainted ]----                
(XEN) CPU:    0                                                                 
(XEN) RIP:    e008:[<ffff828c8017e343>] do_device_not_available+0x44/0xbc       
(XEN) RFLAGS: 0000000000010246   CONTEXT: hypervisor                            
(XEN) rax: 0000000000000000   rbx: ffff83007d40e080   rcx: 0000000000001be0     
(XEN) rdx: ffff828c8028ff28   rsi: 000000000000000a   rdi: ffff828c8028e348     
(XEN) rbp: ffff828c8028e338   rsp: ffff828c8028e318   r8:  ffff828c8028fe28     
(XEN) r9:  ffff828c801c52fe   r10: 000000000fff00b0   r11: ffff828c801c54e6     
(XEN) r12: 0000000000000000   r13: 0000000000000000   r14: 0000000000000000     
(XEN) r15: 0000000000000000   cr0: 000000008005003b   cr4: 00000000000026b0     
(XEN) cr3: 0000000079183000   cr2: 0000000000000000                             
(XEN) ds: 0000   es: 0000   fs: 0000   gs: 0000   ss: e010   cs: e008           
...
(XEN)    [<ffff828c8017e343>] do_device_not_available+0x44/0xbc                 
(XEN)    [<ffff828c801f95b5>] handle_exception_saved+0x2d/0x6b                  
(XEN)    [<ffff828c801c54e6>] realmode_emulate_cmpxchg+0x0/0x3b                 
(XEN)    [<ffff828c801c52fe>] realmode_emulate_insn_fetch+0x0/0xc3              
(XEN)    [<ffff828c8018ad77>] x86_emulate+0xa267/0x1348c                        

which is

    case 0x9b:  /* wait/fwait */
        __emulate_fpu_insn("fwait");
        break;

I guess we need to ensure that the FPU is setup before emulating FPU
instructions?

Samuel