Messages in this thread | | | Subject | Re: [PATCH 3.16 31/72] KVM: x86: Manually calculate reserved bits when loading PDPTRS | From | Ben Hutchings <> | Date | Tue, 10 Dec 2019 16:16:44 +0000 |
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On Mon, 2019-12-09 at 07:49 -0800, Sean Christopherson wrote: > On Sun, Dec 08, 2019 at 01:53:15PM +0000, Ben Hutchings wrote: > > 3.16.79-rc1 review patch. If anyone has any objections, please let me know. > > > > ------------------ > > > > From: Sean Christopherson <sean.j.christopherson@intel.com> > > > > commit 16cfacc8085782dab8e365979356ce1ca87fd6cc upstream. > > You'll also want to pull in two PAE related fixes (in this order): > > d35b34a9a70e ("kvm: mmu: Don't read PDPTEs when paging is not enabled")
I've added this, thanks.
> bf03d4f93347 ("KVM: x86: introduce is_pae_paging") > > The "introduce is_pae_paging" has an undocumented bug fix. IIRC it > manifests as an unexpected #GP on MOV CR3 in 64-bit mode. Here's the blurb > I added to the backports for 4.x. > > Moving to the common helper also fixes a subtle bug in kvm_set_cr3() > where it fails to check is_long_mode() and results in KVM incorrectly > attempting to load PDPTRs for a 64-bit guest.
The 3.16, 4.4, and 4.9 branches have slightly different conditions in kvm_set_cr3():
if (is_long_mode(vcpu)) { if (cr3 & CR3_L_MODE_RESERVED_BITS) return 1; } else if (is_pae(vcpu) && is_paging(vcpu) && !load_pdptrs(vcpu, vcpu->arch.walk_mmu, cr3)) return 1;
So load_pdptrs() already won't be called if is_long_mode() returns true, and this fix shouldn't be needed.
Ben.
-- Ben Hutchings Experience is directly proportional to the value of equipment destroyed - Carolyn Scheppner
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