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Re: [Xen-devel] Intel: GPF from lret to load CS with weird error code

>>> Mukesh Rathor <mukesh.rathor@xxxxxxxxxx> 05/30/13 4:02 AM >>>
>Guest (PVH) is running in vmx in 64bit mode,  it loads CS:
>ffffffff810034d2: 2:load_cs+12                   push $0x10              
>ffffffff810034d4: 2:load_cs+14                   lea 0x2(%rip), %rax     
>ffffffff810034db: 2:load_cs+1b                   push %rax               
>ffffffff810034dc: 2:load_cs+1c                   lret                    
>The lret causes a GP. But the error code is strange (0xfffc):

This is a strong hint at the lret lacking a REX64 override, and hence the high 
32 bits
of the intended RIP being taken as target CS. lret, other than ret, doesn't 
default to
64 bit operand size.


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