Re: with kerenl 2.6.27, CONFIG_KVM_GUEST does not work

[Marcelo Tosatti <mtosatti@redhat.com>]

On Fri, Oct 10, 2008 at 06:11:08PM +0200, xming wrote:
> Kernel 2.6.27 + kvm-76 on the host really gives some performance boost here.
> but:
> 
> When running 2.6.27 compiled with CONFIG_KVM_GUEST=y in the guest, the guest
> won't start, lot's of segfaults (in the guest)  especially udev initializations.
> 
> unset CONFIG_KVM_GUEST=y, then the guest runs fine

Does the attached work for you?

Avi, do you have thoughts on how to proceed with pvmmu? Using hypercalls
instead of faults can still be beneficial (for the first write before
page goes out of sync, or for non-leaf tables which currently don't go
oos). But at the current state pvmmu should be slower in most loads.
Perhaps disable it?

KVM: MMU: sync root on paravirt TLB flush

The pvmmu TLB flush handler should request a root sync, similarly to
a native read-write CR3.

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 79cb4a9..7e70e97 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -2747,6 +2747,7 @@ static int kvm_pv_mmu_write(struct kvm_vcpu *vcpu,
 static int kvm_pv_mmu_flush_tlb(struct kvm_vcpu *vcpu)
 {
 	kvm_x86_ops->tlb_flush(vcpu);
+	set_bit(KVM_REQ_MMU_SYNC, &vcpu->requests);
 	return 1;
 }