From b7b7c4df2d251b1feba217939ea0b618094a48c2 Mon Sep 17 00:00:00 2001
From: Jan Beulich <jbeulich@suse.com>
Date: Thu, 28 Jun 2018 12:27:56 +0200
Subject: [PATCH] x86/EFI: further correct FPU state handling around runtime
 calls

We must not leave a vCPU with CR0.TS clear when it is not in fully eager
mode and has not touched non-lazy state. Instead of adding a 3rd
invocation of stts() to vcpu_restore_fpu_eager(), consolidate all of
them into a single one done at the end of the function.

Rename the function at the same time to better reflect its purpose, as
the patches touches all of its occurences anyway.

The new function parameter is not really well named, but
"need_stts_if_not_fully_eager" seemed excessive to me.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Paul Durrant <paul.durrant@citrix.com>
---
 xen/arch/x86/domain.c      |  2 +-
 xen/arch/x86/i387.c        | 10 ++++++----
 xen/common/efi/runtime.c   |  2 +-
 xen/include/asm-x86/i387.h |  2 +-
 4 files changed, 9 insertions(+), 7 deletions(-)

diff --git a/xen/arch/x86/domain.c b/xen/arch/x86/domain.c
index 0eb377a2f2..2b798bb1d0 100644
--- a/xen/arch/x86/domain.c
+++ b/xen/arch/x86/domain.c
@@ -1703,7 +1703,7 @@ static void __context_switch(void)
             if ( xcr0 != get_xcr0() && !set_xcr0(xcr0) )
                 BUG();
         }
-        vcpu_restore_fpu_eager(n);
+        vcpu_restore_fpu_nonlazy(n, 0);
         n->arch.ctxt_switch_to(n);
     }
 
diff --git a/xen/arch/x86/i387.c b/xen/arch/x86/i387.c
index 28edfce67f..e2f5cca440 100644
--- a/xen/arch/x86/i387.c
+++ b/xen/arch/x86/i387.c
@@ -212,7 +212,7 @@ static inline void fpu_fsave(struct vcpu *v)
 /*       VCPU FPU Functions    */
 /*******************************/
 /* Restore FPU state whenever VCPU is schduled in. */
-void vcpu_restore_fpu_eager(struct vcpu *v)
+void vcpu_restore_fpu_nonlazy(struct vcpu *v, bool_t need_stts)
 {
     if ( v->arch.fully_eager_fpu )
     {
@@ -230,8 +230,7 @@ void vcpu_restore_fpu_eager(struct vcpu *v)
         v->fpu_dirtied = 1;
 
         /* Xen doesn't need TS set, but the guest might. */
-        if ( is_pv_vcpu(v) && (v->arch.pv_vcpu.ctrlreg[0] & X86_CR0_TS) )
-            stts();
+        need_stts = is_pv_vcpu(v) && (v->arch.pv_vcpu.ctrlreg[0] & X86_CR0_TS);
     }
     /* save the nonlazy extended state which is not tracked by CR0.TS bit */
     else if ( v->arch.nonlazy_xstate_used )
@@ -241,8 +240,11 @@ void vcpu_restore_fpu_eager(struct vcpu *v)
         /* Avoid recursion */
         clts();        
         fpu_xrstor(v, XSTATE_NONLAZY);
-        stts();
+        need_stts = 1;
     }
+
+    if ( need_stts )
+        stts();
 }
 
 /* 
diff --git a/xen/common/efi/runtime.c b/xen/common/efi/runtime.c
index 309b13a70f..75f119315a 100644
--- a/xen/common/efi/runtime.c
+++ b/xen/common/efi/runtime.c
@@ -128,7 +128,7 @@ void efi_rs_leave(struct efi_rs_state *state)
     irq_exit();
     efi_rs_on_cpu = NR_CPUS;
     spin_unlock(&efi_rs_lock);
-    vcpu_restore_fpu_eager(curr);
+    vcpu_restore_fpu_nonlazy(curr, 1);
 }
 
 bool_t efi_rs_using_pgtables(void)
diff --git a/xen/include/asm-x86/i387.h b/xen/include/asm-x86/i387.h
index 150a09e41f..64e277e656 100644
--- a/xen/include/asm-x86/i387.h
+++ b/xen/include/asm-x86/i387.h
@@ -35,7 +35,7 @@ struct ix87_state {
     } r[8];
 };
 
-void vcpu_restore_fpu_eager(struct vcpu *v);
+void vcpu_restore_fpu_nonlazy(struct vcpu *v, bool_t need_stts);
 void vcpu_restore_fpu_lazy(struct vcpu *v);
 void vcpu_save_fpu(struct vcpu *v);
 void save_fpu_enable(void);