KVM: Fix PDPTR reloading on CR4 writes

(cherry picked from commit a2edf57f510cce6a389cc14e58c6ad0a4296d6f9)

The processor is documented to reload the PDPTRs while in PAE mode if any
of the CR4 bits PSE, PGE, or PAE change.  Linux relies on this
behaviour when zapping the low mappings of PAE kernels during boot.

The code already handled changes to CR4.PAE; augment it to also notice changes
to PSE and PGE.

This triggered while booting an F11 PAE kernel; the futex initialization code
runs before any CR3 reloads and writes to a NULL pointer; the futex subsystem
ended up uninitialized, killing PI futexes and pulseaudio which uses them.

Signed-off-by: Avi Kivity <avi@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 662cf12d1db9436ea06e844ae7fce19219ba98d3..cfc2641e0b231388ab1c2b02f00c03f1c7e0afb5 100644 (file)
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -318,6 +318,9 @@ EXPORT_SYMBOL_GPL(kvm_lmsw);
 
 void kvm_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4)
 {
+       unsigned long old_cr4 = vcpu->arch.cr4;
+       unsigned long pdptr_bits = X86_CR4_PGE | X86_CR4_PSE | X86_CR4_PAE;
+
        if (cr4 & CR4_RESERVED_BITS) {
                printk(KERN_DEBUG "set_cr4: #GP, reserved bits\n");
                kvm_inject_gp(vcpu, 0);
@@ -331,7 +334,8 @@ void kvm_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4)
                        kvm_inject_gp(vcpu, 0);
                        return;
                }
-       } else if (is_paging(vcpu) && !is_pae(vcpu) && (cr4 & X86_CR4_PAE)
+       } else if (is_paging(vcpu) && (cr4 & X86_CR4_PAE)
+                  && ((cr4 ^ old_cr4) & pdptr_bits)
                   && !load_pdptrs(vcpu, vcpu->arch.cr3)) {
                printk(KERN_DEBUG "set_cr4: #GP, pdptrs reserved bits\n");
                kvm_inject_gp(vcpu, 0);