lguest, x86: handle guest TS bit for lazy/non-lazy fpu host models

Instead of using unlazy_fpu() check if user_has_fpu() and set/clear
the host TS bits so that the lguest works fine with both the
lazy/non-lazy FPU host models with minimal changes.

Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Link: http://lkml.kernel.org/r/1345842782-24175-6-git-send-email-suresh.b.siddha@intel.com
Cc: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>

1 files changed, 7 insertions, 3 deletions

diff --git a/drivers/lguest/x86/core.c b/drivers/lguest/x86/core.c
index 39809035320a..4af12e1844d5 100644
--- a/drivers/lguest/x86/core.c
+++ b/drivers/lguest/x86/core.c
@@ -203,8 +203,8 @@ void lguest_arch_run_guest(struct lg_cpu *cpu)
          * we set it now, so we can trap and pass that trap to the Guest if it
          * uses the FPU.
          */
-        if (cpu->ts)
-                unlazy_fpu(current);
+        if (cpu->ts && user_has_fpu())
+                stts();
 
         /*
          * SYSENTER is an optimized way of doing system calls.  We can't allow
@@ -234,6 +234,10 @@ void lguest_arch_run_guest(struct lg_cpu *cpu)
          if (boot_cpu_has(X86_FEATURE_SEP))
                 wrmsr(MSR_IA32_SYSENTER_CS, __KERNEL_CS, 0);
 
+        /* Clear the host TS bit if it was set above. */
+        if (cpu->ts && user_has_fpu())
+                clts();
+
         /*
          * If the Guest page faulted, then the cr2 register will tell us the
          * bad virtual address.  We have to grab this now, because once we
@@ -249,7 +253,7 @@ void lguest_arch_run_guest(struct lg_cpu *cpu)
          * a different CPU. So all the critical stuff should be done
          * before this.
          */
-        else if (cpu->regs->trapnum == 7)
+        else if (cpu->regs->trapnum == 7 && !user_has_fpu())
                 math_state_restore();
 }