[Xen-changelog] [xen stable-4.8] x86/EFI: further correct FPU state handling around runtime calls

[patchbot@xxxxxxx]

commit 9a7fa685f999c5166f3a4688e2596f3a9f36a9cf
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Thu Jun 28 11:20:24 2018 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Thu Jun 28 11:20:24 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 <jbeulich@xxxxxxxx>
    Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    Reviewed-by: Paul Durrant <paul.durrant@xxxxxxxxxx>
    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 ab10e878fc..51823f0edd 100644
--- a/xen/arch/x86/domain.c
+++ b/xen/arch/x86/domain.c
@@ -2168,7 +2168,7 @@ 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, false);
         n->arch.ctxt_switch_to(n);
     }
 
diff --git a/xen/arch/x86/i387.c b/xen/arch/x86/i387.c
index 992d4d21c1..b89ee9a3dc 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 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 = true;
     }
+
+ maybe_stts:
+    if ( need_stts )
+        stts();
 }
 
 /* 
diff --git a/xen/common/efi/runtime.c b/xen/common/efi/runtime.c
index 65402e2d1f..a78e11bfca 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, true);
 }
 
 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..243de672eb 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 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-4.8

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