On Thu, Mar 06, 2008 at 04:44:26PM +0200, Avi Kivity wrote: > Marcelo Tosatti wrote: > >> > >>Here CR3_TARGET_VALUEx is written. > >>My question is: > >>1 why is vmcs_writel(CR3_TARGET_VALUE0 + idx*2, cr3); called by > >>vmx_set_cr3(), but not called by mmu_free_roots()? > >> > > > >By clearing guest_cr3 entry of the shared area we avoid the guest from > >using it. > > > >So its unecessary to also clear the corresponding CR3_TARGET_VALUE0 > >register. > > > > > >>2 since "cache" is also mapped to guest OS. Is calling > >>vmcs_writel(CR3_TARGET_VALUE0 + idx*2, cr3); necessary? > >> > > > >As said above, no, because the guest will check > >cache->entry[idx].guest_cr3 before attempting to use a cached host_cr3 > >value. > > > > > Only if you trust the guest.
If a guest manages to catch a stale entry in the CR3_TARGET_VALUE0 register it will hit: + /* + * Figure out whether vcpu->cr3 needs updating because + * the guest made use of the cr3 cache. + */ + kvm_cr3_cache_sync(vcpu); + WARN_ON(vmcs_readl(GUEST_CR3) != vcpu->arch.mmu.root_hpa[vcpu->arch.cr3_cache_idx]); And have the shadow root table pointer unsynced with its cr3. I can't see how it could cause any damage to the host (the guest is will very likely die due to that). ------------------------------------------------------------------------- This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2008. http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/ _______________________________________________ kvm-devel mailing list kvm-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/kvm-devel
