On Mon, 2007-08-27 at 10:16 -0500, Anthony Liguori wrote:
> This patch refactors the current hypercall infrastructure to better support
> live
> migration and SMP. It eliminates the hypercall page by trapping the UD
> exception that would occur if you used the wrong hypercall instruction for the
> underlying architecture and replacing it with the right one lazily.
It also reduces the number of hypercall args, which you don't mention
here.
> + er = emulate_instruction(&svm->vcpu, kvm_run, 0, 0);
> +
> + /* we should only succeed here in the case of hypercalls which
> + cannot generate an MMIO event. MMIO means that the emulator
> + is mistakenly allowing an instruction that should generate
> + a UD fault so it's a bug. */
> + BUG_ON(er == EMULATE_DO_MMIO);
This seems... unwise. Firstly we know our emulator is incomplete.
Secondly an SMP guest can exploit this to crash the host.
(Code is in two places).
> +#define KVM_HYPERCALL ".byte 0x0f,0x01,0xc1"
A nice big comment would be nice here, I think. Note that this is big
enough for both "int $0x1f" and "sysenter", so I'm happy.
Cheers,
Rusty.
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