Re: [Qemu-devel] [PATCH 1/3] target-i386: fix segment flags for SMM, user-mode emulation and VM86 mode

[Paolo Bonzini]

Il 27/05/2014 22:33, Bandan Das ha scritto:
> > With the next patch, these need to be correct or VM86 tasks
> > have the wrong CPL.  The flags are basically what the Intel VMX
> > documentation say is mandatory for entry into a VM86 guest.
>
> Are you referring to 26.3.1.2 ?

Yes:

CS, SS, DS, ES, FS, GS.
If the guest will be virtual-8086, the field must be 000000F3H. This 
implies the following:
- Bits 3:0 (Type) must be 3, indicating an expand-up read/write accessed 
data segment.
- Bit 4 (S) must be 1.
- Bits 6:5 (DPL) must be 3.
- Bit 7 (P) must be 1.
- Bits 11:8 (reserved), bit 12 (software available), bit 13 
(reserved/L), bit 14 (D/B), bit 15 (G), bit 16 (unusable), and bits 
31:17 (reserved) must all be 0.

Paolo

> Just a nit, I guess it helps
> to add a pointer in the comments for someone (like me :)) going
> through the code.