Messages in this thread | | | Subject | Re: [PATCH 2/3] Refactor hypercall infrastructure | From | Rusty Russell <> | Date | Wed, 29 Aug 2007 04:12:57 +1000 |
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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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