From 106b3e94801d4f076a027ab525f7bcafe230b1fc Mon Sep 17 00:00:00 2001
From: Marcelo Tosatti <mtosatti@redhat.com>
Date: Mon, 15 Jun 2009 18:49:23 -0300
Subject: [PATCH 3/3] KVM: Fix PDPTR reloading on CR4 writes

KVM: Fix PDPTR reloading on CR4 writes

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>
Message-ID: <20090615214923.GB26899@amt.cnet>
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
Acked-by: Avi Kivity <avi@redhat.com>
Acked-by: Juan Quintela <quintela@redhat.com>
Acked-by: Andrea Arcangeli <aarcange@redhat.com>
Bugzilla: 504237
---
 arch/x86/kvm/x86.c |    6 +++++-
 1 files changed, 5 insertions(+), 1 deletions(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 0cbdf14..80abb6a 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -334,6 +334,9 @@ 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);
@@ -347,7 +350,8 @@ 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);
-- 
1.6.3.rc4.29.g8146