[xen stable-4.7] x86/EFI: further correct FPU state handling around runtime calls

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[xen stable-4.7] x86/EFI: further correct FPU state handling around runtime calls

patchbot
commit 839826b094a068139fa38e56e52e9f054cca8823
Author:     Jan Beulich <[hidden email]>
AuthorDate: Thu Jun 28 11:29:48 2018 +0200
Commit:     Jan Beulich <[hidden email]>
CommitDate: Thu Jun 28 11:29:48 2018 +0200

    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 <[hidden email]>
    Reviewed-by: Andrew Cooper <[hidden email]>
    Reviewed-by: Paul Durrant <[hidden email]>
    master commit: 23839a0fa0bbe78c174cd2bb49083e153f0f99df
    master date: 2018-06-26 15:23:08 +0200
---
 xen/arch/x86/domain.c      |  2 +-
 xen/arch/x86/i387.c        | 13 ++++++++-----
 xen/common/efi/runtime.c   |  2 +-
 xen/include/asm-x86/i387.h |  2 +-
 4 files changed, 11 insertions(+), 8 deletions(-)

diff --git a/xen/arch/x86/domain.c b/xen/arch/x86/domain.c
index a3e913b162..596be5c4f5 100644
--- a/xen/arch/x86/domain.c
+++ b/xen/arch/x86/domain.c
@@ -2147,7 +2147,7 @@ static void __context_switch(void)
             if ( cpu_has_xsaves && has_hvm_container_vcpu(n) )
                 set_msr_xss(n->arch.hvm_vcpu.msr_xss);
         }
-        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 992d4d21c1..286847148a 100644
--- a/xen/arch/x86/i387.c
+++ b/xen/arch/x86/i387.c
@@ -207,11 +207,11 @@ static inline void fpu_fxsave(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)
 {
     /* Restore nonlazy extended state (i.e. parts not tracked by CR0.TS). */
     if ( !v->arch.fully_eager_fpu && !v->arch.nonlazy_xstate_used )
-        return;
+        goto maybe_stts;
 
     ASSERT(!is_idle_vcpu(v));
 
@@ -234,14 +234,17 @@ 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);
     }
     else
     {
         fpu_xrstor(v, XSTATE_NONLAZY);
-        stts();
+        need_stts = 1;
     }
+
+ maybe_stts:
+    if ( need_stts )
+        stts();
 }
 
 /*
diff --git a/xen/common/efi/runtime.c b/xen/common/efi/runtime.c
index 65402e2d1f..f53101a5e5 100644
--- a/xen/common/efi/runtime.c
+++ b/xen/common/efi/runtime.c
@@ -130,7 +130,7 @@ 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 7cfa215d30..5a4d778033 100644
--- a/xen/include/asm-x86/i387.h
+++ b/xen/include/asm-x86/i387.h
@@ -28,7 +28,7 @@ struct ix87_env {
     uint16_t fds, _res6;
 };
 
-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);
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.7

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