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

[Roger Pau Monne <roger.pau@xxxxxxxxxx>]

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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