Messages in this thread | | | From | Jim Mattson <> | Date | Tue, 14 Jul 2020 11:55:45 -0700 | Subject | Re: [PATCH] KVM: x86: Don't attempt to load PDPTRs when 64-bit mode is enabled |
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On Mon, Jul 13, 2020 at 6:57 PM Sean Christopherson <sean.j.christopherson@intel.com> wrote: > > Don't attempt to load PDPTRs if EFER.LME=1, i.e. if 64-bit mode is > enabled. A recent change to reload the PDTPRs when CR0.CD or CR0.NW is > toggled botched the EFER.LME handling and sends KVM down the PDTPR path > when is_paging() is true, i.e. when the guest toggles CD/NW in 64-bit > mode.
Oops!
I don't think "is_paging()" is relevant here, so much as "EFER.LME=1." As you note below, KVM *should* go down the PDPTR path when is_paging() is true and EFER.LME=0.
> Split the CR0 checks for 64-bit vs. 32-bit PAE into separate paths. The > 64-bit path is specifically checking state when paging is toggled on, > i.e. CR0.PG transititions from 0->1. The PDPTR path now needs to run if > the new CR0 state has paging enabled, irrespective of whether paging was > already enabled. Trying to shave a few cycles to make the PDPTR path an > "else if" case is a mess. > > Fixes: d42e3fae6faed ("kvm: x86: Read PDPTEs on CR0.CD and CR0.NW changes") > Cc: Jim Mattson <jmattson@google.com> > Cc: Oliver Upton <oupton@google.com> > Cc: Peter Shier <pshier@google.com> > Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com> Reviewed-by: Jim Mattson <jmattson@google.com>
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