Messages in this thread |  | | | Date | Thu, 2 Sep 2010 18:29:34 +0200 | | From | "Roedel, Joerg" <> | | Subject | Re: [PATCH 2/3] KVM: SVM: Restore correct registers after sel_cr0 intercept emulation |
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On Thu, Sep 02, 2010 at 12:02:02PM -0400, Avi Kivity wrote: > On 09/02/2010 06:29 PM, Joerg Roedel wrote: > > This patch implements restoring of the correct rip, rsp, and > > rax after the svm emulation in KVM injected a selective_cr0 > > write intercept into the guest hypervisor. The problem was > > that the vmexit is emulated in the instruction emulation > > which later commits the registers right after the write-cr0 > > instruction. So the l1 guest will continue to run with the > > l2 rip, rsp and rax resulting in unpredictable behavior. > > Please post a unit test for this.
Will do. Should be an easy test.
> > This patch is not the final word, it is just an easy patch > > to fix the issue. The real fix will be done when the > > instruction emulator is made aware of nested virtualization. > > Until this is done this patch fixes the issue and provides > > an easy way to fix this in -stable too. > > I agree. We can probably use X86EMUL_PROPAGATE_FAULT to abort > emulation, but looking at the code, it will take some refactoring.
I thought of an X86EMUL_INTERCEPTED. An architecture specific function is called after instruction decoding which checks if an intercept is necessary. If it returns X86EMUL_INTERCEPTED then the instruction emulation is discarded and kvm goes straight back into the guest.
Joerg
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