File 53a199d7-x86-EFI-allow-FPU-XMM-use-in-runtime-s... of Package xen

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File 53a199d7-x86-EFI-allow-FPU-XMM-use-in-runtime-service-functions.patch of Package xen (Revision 79cea1abf747b2e33b174bb25b29f240)

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References: bnc#882127

# Commit e0fe297dabc96d8161d568f19a99722c4739b9f9
# Date 2014-06-18 15:53:27 +0200
# Author Jan Beulich <jbeulich@suse.com>
# Committer Jan Beulich <jbeulich@suse.com>
x86/EFI: allow FPU/XMM use in runtime service functions

UEFI spec update 2.4B developed a requirement to enter runtime service
functions with CR0.TS (and CR0.EM) clear, thus making feasible the
already previously stated permission for these functions to use some of
the XMM registers. Enforce this requirement (along with the connected
ones on FPU control word and MXCSR) by going through a full FPU save
cycle (if the FPU was dirty) in efi_rs_enter() (along with loading  the
specified values into the other two registers).

Note that the UEFI spec mandates that extension registers other than
XMM ones (for our purposes all that get restored eagerly) are preserved
across runtime function calls, hence there's nothing we need to restore
in efi_rs_leave() (they do get saved, but just for simplicity's sake).

Signed-off-by: Jan Beulich <jbeulich@suse.com>

--- a/xen/arch/x86/efi/runtime.c
+++ b/xen/arch/x86/efi/runtime.c
@@ -10,6 +10,8 @@ DEFINE_XEN_GUEST_HANDLE(CHAR16);
 
 #ifndef COMPAT
 
+# include <asm/i387.h>
+# include <asm/xstate.h>
 # include <public/platform.h>
 
 const bool_t efi_enabled = 1;
@@ -45,8 +47,14 @@ const struct efi_pci_rom *__read_mostly 
 
 unsigned long efi_rs_enter(void)
 {
+    static const u16 fcw = FCW_DEFAULT;
+    static const u32 mxcsr = MXCSR_DEFAULT;
     unsigned long cr3 = read_cr3();
 
+    save_fpu_enable();
+    asm volatile ( "fldcw %0" :: "m" (fcw) );
+    asm volatile ( "ldmxcsr %0" :: "m" (mxcsr) );
+
     spin_lock(&efi_rs_lock);
 
     /* prevent fixup_page_fault() from doing anything */
@@ -82,6 +90,7 @@ void efi_rs_leave(unsigned long cr3)
     }
     irq_exit();
     spin_unlock(&efi_rs_lock);
+    stts();
 }
 
 unsigned long efi_get_time(void)
--- a/xen/arch/x86/i387.c
+++ b/xen/arch/x86/i387.c
@@ -266,10 +266,10 @@ void vcpu_restore_fpu_lazy(struct vcpu *
  * On each context switch, save the necessary FPU info of VCPU being switch 
  * out. It dispatches saving operation based on CPU's capability.
  */
-void vcpu_save_fpu(struct vcpu *v)
+static bool_t _vcpu_save_fpu(struct vcpu *v)
 {
     if ( !v->fpu_dirtied && !v->arch.nonlazy_xstate_used )
-        return;
+        return 0;
 
     ASSERT(!is_idle_vcpu(v));
 
@@ -284,9 +284,22 @@ void vcpu_save_fpu(struct vcpu *v)
         fpu_fsave(v);
 
     v->fpu_dirtied = 0;
+
+    return 1;
+}
+
+void vcpu_save_fpu(struct vcpu *v)
+{
+    _vcpu_save_fpu(v);
     stts();
 }
 
+void save_fpu_enable(void)
+{
+    if ( !_vcpu_save_fpu(current) )
+        clts();
+}
+
 /* Initialize FPU's context save area */
 int vcpu_init_fpu(struct vcpu *v)
 {
--- a/xen/include/asm-x86/i387.h
+++ b/xen/include/asm-x86/i387.h
@@ -38,6 +38,7 @@ struct ix87_state {
 void vcpu_restore_fpu_eager(struct vcpu *v);
 void vcpu_restore_fpu_lazy(struct vcpu *v);
 void vcpu_save_fpu(struct vcpu *v);
+void save_fpu_enable(void);
 
 int vcpu_init_fpu(struct vcpu *v);
 void vcpu_destroy_fpu(struct vcpu *v);

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File 53a199d7-x86-EFI-allow-FPU-XMM-use-in-runtime-service-functions.patch of Package xen (Revision 79cea1abf747b2e33b174bb25b29f240)

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