Re: [PATCH 0/4] VMX: Invalid guest state emulation

[Avi Kivity <avi@qumranet.com>]

Mohammed Gamal wrote:
> The patch series adds invalid guest state emulation for VMX hosts, which is needed in order to properly support real mode guests.
> Usually, a guest would be in an VMX-invalid state during mode switches from real to protected mode or vice versa.
> We handle this invalid state by using the x86 emulator to emulate instructions until we arrive back to a VMX-friendly state.
> This is achieved by:
> - Adding thorough guest state checking in order to catch and handle invalid states
> - Adding a guest state handler which emulates instructions till guest state is valid
> - Adding an "emulation required" flag, enabled on mode switches, to indicated that emulation is needed 
> - Checking for guest state on vcpu_run() and emulating instructions instead of entering VMX if the state is invalid.
>
> The next step needed is to add more instructions to the x86 emulator, since we might run into instructions not supported yet.
> In order not to interfere with normal KVM operation, a module parameter 'emulate_invalid_guest_state' -which is disabled by default- that is used in 
> order to drive emulation. Bear in mind that currently you can't use this patch alone to get real mode guests to work. There is still a lot of work 
> needed on the x86 emulator in order not to run into failures running these guests.
>   

Thanks, all applied.

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