Re: [Xen-devel] [PATCH 2/2] pvh: set only minimal cr0 and cr4 flags in order to use paging

["Dong, Eddie" <eddie.dong@xxxxxxxxx>]

Acked-by Eddie Dong <eddie.dong@xxxxxxxxx>

-----Original Message-----
From: xen-devel-bounces@xxxxxxxxxxxxx [mailto:xen-devel-bounces@xxxxxxxxxxxxx] 
On Behalf Of Roger Pau Monne
Sent: Tuesday, November 19, 2013 8:35 PM
To: xen-devel@xxxxxxxxxxxxxxxxxxxx
Cc: Keir Fraser; George Dunlap; Tim Deegan; Jan Beulich; Roger Pau Monne
Subject: [Xen-devel] [PATCH 2/2] pvh: set only minimal cr0 and cr4 flags in 
order to use paging

Right now Xen sets the WP and NE flags on cr0 for PVH, which are not needed in 
order to boot with paging enabled. The same happens with cr4, at least on my 
system OSFXSR, OSXMMEXCPT and MCE are enabled by default when there's no need.

Signed-off-by: Roger Pau Monnà <roger.pau@xxxxxxxxxx>
Cc: George Dunlap <george.dunlap@xxxxxxxxxxxxx>
Cc: Mukesh Rathor <mukesh.rathor@xxxxxxxxxx>
Cc: Jan Beulich <JBeulich@xxxxxxxx>
Cc: Tim Deegan <tim@xxxxxxx>
Cc: Keir Fraser <keir@xxxxxxx>
---
 xen/arch/x86/hvm/vmx/vmcs.c |    7 ++-----
 1 files changed, 2 insertions(+), 5 deletions(-)

diff --git a/xen/arch/x86/hvm/vmx/vmcs.c b/xen/arch/x86/hvm/vmx/vmcs.c index 
290b42f..33e2544 100644
--- a/xen/arch/x86/hvm/vmx/vmcs.c
+++ b/xen/arch/x86/hvm/vmx/vmcs.c
@@ -28,7 +28,6 @@
 #include <asm/msr.h>
 #include <asm/xstate.h>
 #include <asm/hvm/hvm.h>
-#include <asm/hvm/nestedhvm.h>
 #include <asm/hvm/io.h>
 #include <asm/hvm/support.h>
 #include <asm/hvm/vmx/vmx.h>
@@ -1089,13 +1088,11 @@ static int construct_vmcs(struct vcpu *v)
 
     /* PVH domains always start in paging mode */
     if ( is_pvh_domain(d) )
-        v->arch.hvm_vcpu.guest_cr[0] |= X86_CR0_PG | X86_CR0_NE | X86_CR0_WP;
+        v->arch.hvm_vcpu.guest_cr[0] |= X86_CR0_PG;
 
     hvm_update_guest_cr(v, 0);
 
-    v->arch.hvm_vcpu.guest_cr[4] = is_pvh_domain(d) ?
-        (real_cr4_to_pv_guest_cr4(mmu_cr4_features)
-         & ~HVM_CR4_GUEST_RESERVED_BITS(v)) : 0;
+    v->arch.hvm_vcpu.guest_cr[4] = is_pvh_domain(d) ? X86_CR4_PAE : 0;
     hvm_update_guest_cr(v, 4);
 
     if ( cpu_has_vmx_tpr_shadow )
--
1.7.7.5 (Apple Git-26)


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