linux-kernel - [PATCH v2 4/6] xen/x86/pvh: Set up descriptors for 32-bit PVH guests

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Date:	Thu, 16 Jul 2015 17:43:39 -0400
From:	Boris Ostrovsky <boris.ostrovsky@...cle.com>
To:	david.vrabel@...rix.com, konrad.wilk@...cle.com
Cc:	roger.pau@...rix.com, elena.ufimtseva@...cle.com,
	stefano.stabellini@...citrix.com, tim@....org, jbeulich@...e.com,
	andrew.cooper3@...rix.com, ian.campbell@...rix.com,
	ian.jackson@...citrix.com, xen-devel@...ts.xenproject.org,
	linux-kernel@...r.kernel.org, boris.ostrovsky@...cle.com
Subject: [PATCH v2 4/6] xen/x86/pvh: Set up descriptors for 32-bit PVH guests

Signed-off-by: Boris Ostrovsky <boris.ostrovsky@...cle.com>
---
Changes in v2:
* Set segment selectors using loadsegment() instead of assembly

 arch/x86/xen/enlighten.c | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index f8dc398..d665b1d 100644
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -1362,12 +1362,12 @@ static void __init xen_boot_params_init_edd(void)
 static void __ref xen_setup_gdt(int cpu)
 {
 	if (xen_feature(XENFEAT_auto_translated_physmap)) {
-#ifdef CONFIG_X86_64
-		unsigned long dummy;
+		unsigned long __attribute__((unused)) dummy;
 
-		load_percpu_segment(cpu); /* We need to access per-cpu area */
+		setup_stack_canary_segment(cpu);
 		switch_to_new_gdt(cpu); /* GDT and GS set */
 
+#ifdef CONFIG_X86_64
 		/* We are switching of the Xen provided GDT to our HVM mode
 		 * GDT. The new GDT has  __KERNEL_CS with CS.L = 1
 		 * and we are jumping to reload it.
@@ -1392,8 +1392,13 @@ static void __ref xen_setup_gdt(int cpu)
 		loadsegment(ds, 0);
 		loadsegment(fs, 0);
 #else
-		/* PVH: TODO Implement. */
-		BUG();
+		asm volatile ("ljmp %0,$1f\n"
+			      "1:\n"
+			      :: "i" (__KERNEL_CS));
+
+		loadsegment(ss, __KERNEL_DS);
+		loadsegment(ds, __USER_DS);
+		loadsegment(es, __USER_DS);
 #endif
 		return; /* PVH does not need any PV GDT ops. */
 	}
-- 
1.8.1.4

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