[Xen-devel] [V0 PATCH] xen/pvh: set some cr flags upon vcpu start

[Mukesh Rathor <mukesh.rathor@xxxxxxxxxx>]

pvh was designed to start with pv flags, but a commit in xen tree
51e2cac257ec8b4080d89f0855c498cbbd76a5e5 removed some of the flags as
they are not necessary. As a result, these CR flags must be set in the
guest.

Signed-off-by: Roger Pau Monne <roger.pau@xxxxxxxxxx>
Signed-off-by: Mukesh Rathor <mukesh.rathor@xxxxxxxxxx>
---
 arch/x86/xen/enlighten.c |   43 +++++++++++++++++++++++++++++++++++++------
 arch/x86/xen/smp.c       |    2 +-
 arch/x86/xen/xen-ops.h   |    2 +-
 3 files changed, 39 insertions(+), 8 deletions(-)

diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index 628099a..4a2aaa6 100644
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -1410,12 +1410,8 @@ static void __init xen_boot_params_init_edd(void)
  * Set up the GDT and segment registers for -fstack-protector.  Until
  * we do this, we have to be careful not to call any stack-protected
  * function, which is most of the kernel.
- *
- * Note, that it is refok - because the only caller of this after init
- * is PVH which is not going to use xen_load_gdt_boot or other
- * __init functions.
  */
-void __ref xen_setup_gdt(int cpu)
+static void xen_setup_gdt(int cpu)
 {
        if (xen_feature(XENFEAT_auto_translated_physmap)) {
 #ifdef CONFIG_X86_64
@@ -1463,13 +1459,48 @@ void __ref xen_setup_gdt(int cpu)
        pv_cpu_ops.load_gdt = xen_load_gdt;
 }
 
+/*
+ * A pv guest starts with default flags that are not set for pvh, set them
+ * here asap.
+ */
+static void xen_pvh_set_cr_flags(int cpu)
+{
+       write_cr0(read_cr0() | X86_CR0_MP | X86_CR0_WP | X86_CR0_AM);
+
+       if (!cpu)
+               return;
+       /*
+        * Unlike PV, for pvh xen does not set: PSE PGE OSFXSR OSXMMEXCPT
+        * For BSP, PSE PGE will be set in probe_page_size_mask(), for AP
+        * set them here. For all, OSFXSR OSXMMEXCPT will be set in fpu_init
+        */
+       if (cpu_has_pse)
+               set_in_cr4(X86_CR4_PSE);
+
+       if (cpu_has_pge)
+               set_in_cr4(X86_CR4_PGE);
+}
+
+/*
+ * Note, that it is refok - because the only caller of this after init
+ * is PVH which is not going to use xen_load_gdt_boot or other
+ * __init functions.
+ */
+void __ref xen_pvh_secondary_vcpu_init(int cpu)
+{
+       xen_setup_gdt(cpu);
+       xen_pvh_set_cr_flags(cpu);
+}
+
 static void __init xen_pvh_early_guest_init(void)
 {
        if (!xen_feature(XENFEAT_auto_translated_physmap))
                return;
 
-       if (xen_feature(XENFEAT_hvm_callback_vector))
+       if (xen_feature(XENFEAT_hvm_callback_vector)) {
                xen_have_vector_callback = 1;
+               xen_pvh_set_cr_flags(0);
+       }
 
 #ifdef CONFIG_X86_32
        BUG(); /* PVH: Implement proper support. */
diff --git a/arch/x86/xen/smp.c b/arch/x86/xen/smp.c
index 5e46190..a18eadd 100644
--- a/arch/x86/xen/smp.c
+++ b/arch/x86/xen/smp.c
@@ -105,7 +105,7 @@ static void cpu_bringup_and_idle(int cpu)
 #ifdef CONFIG_X86_64
        if (xen_feature(XENFEAT_auto_translated_physmap) &&
            xen_feature(XENFEAT_supervisor_mode_kernel))
-               xen_setup_gdt(cpu);
+               xen_pvh_secondary_vcpu_init(cpu);
 #endif
        cpu_bringup();
        cpu_startup_entry(CPUHP_ONLINE);
diff --git a/arch/x86/xen/xen-ops.h b/arch/x86/xen/xen-ops.h
index 9059c24..1cb6f4c 100644
--- a/arch/x86/xen/xen-ops.h
+++ b/arch/x86/xen/xen-ops.h
@@ -123,5 +123,5 @@ __visible void xen_adjust_exception_frame(void);
 
 extern int xen_panic_handler_init(void);
 
-void xen_setup_gdt(int cpu);
+void xen_pvh_secondary_vcpu_init(int cpu);
 #endif /* XEN_OPS_H */
-- 
1.7.2.3


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