From: kaf24@firebug.cl.cam.ac.uk <kaf24@firebug.cl.cam.ac.uk>
Date: Wed, 5 Oct 2005 15:54:09 +0000 (+0100)
Subject: Emulate guest reads of CR4, masking features that Xen
X-Git-Tag: archive/raspbian/4.8.0-1+rpi1~1^2~16763^2~34
X-Git-Url: https://dgit.raspbian.org/%22http:/www.example.com/cgi/%22https://%22%22/%22http:/www.example.com/cgi/%22https:/%22%22?a=commitdiff_plain;h=e127ae595201d5aa07240b0ad45ac15ef9fead08;p=xen.git

Emulate guest reads of CR4, masking features that Xen
does not export to guests.

Signed-off-by: Keir Fraser <keir@xensource.com>
---

diff --git a/xen/arch/x86/traps.c b/xen/arch/x86/traps.c
index e0f00d3920..44f902f505 100644
--- a/xen/arch/x86/traps.c
+++ b/xen/arch/x86/traps.c
@@ -895,6 +895,14 @@ static int emulate_privileged_op(struct cpu_user_regs *regs)
             *reg = pagetable_get_paddr(v->arch.guest_table);
             break;
 
+        case 4: /* Read CR4 */
+            /*
+             * Guests can read CR4 to see what features Xen has enabled. We
+             * therefore lie about PGE & PSE as they are unavailable to guests.
+             */
+            *reg = read_cr4() & ~(X86_CR4_PGE|X86_CR4_PSE);
+            break;
+
         default:
             goto fail;
         }