1 files changed, 43 insertions, 20 deletions

diff --git a/arch/arm/vfp/vfphw.S b/arch/arm/vfp/vfphw.S
index 9897dcfc16d6..2d30c7f6edd3 100644
--- a/arch/arm/vfp/vfphw.S
+++ b/arch/arm/vfp/vfphw.S
@@ -77,27 +77,27 @@ ENTRY(vfp_support_entry)
         bne     look_for_VFP_exceptions @ VFP is already enabled
 
         DBGSTR1 "enable %x", r10
-        ldr     r3, last_VFP_context_address
+        ldr     r3, vfp_current_hw_state_address
         orr     r1, r1, #FPEXC_EN       @ user FPEXC has the enable bit set
-        ldr     r4, [r3, r11, lsl #2]   @ last_VFP_context pointer
+        ldr     r4, [r3, r11, lsl #2]   @ vfp_current_hw_state pointer
         bic     r5, r1, #FPEXC_EX       @ make sure exceptions are disabled
-        cmp     r4, r10
-        beq     check_for_exception     @ we are returning to the same
-                                        @ process, so the registers are
-                                        @ still there.  In this case, we do
-                                        @ not want to drop a pending exception.
+        cmp     r4, r10                 @ this thread owns the hw context?
+#ifndef CONFIG_SMP
+        @ For UP, checking that this thread owns the hw context is
+        @ sufficient to determine that the hardware state is valid.
+        beq     vfp_hw_state_valid
+
+        @ On UP, we lazily save the VFP context.  As a different
+        @ thread wants ownership of the VFP hardware, save the old
+        @ state if there was a previous (valid) owner.
 
         VFPFMXR FPEXC, r5               @ enable VFP, disable any pending
                                         @ exceptions, so we can get at the
                                         @ rest of it
 
-#ifndef CONFIG_SMP
-        @ Save out the current registers to the old thread state
-        @ No need for SMP since this is not done lazily
-
         DBGSTR1 "save old state %p", r4
-        cmp     r4, #0
-        beq     no_old_VFP_process
+        cmp     r4, #0                  @ if the vfp_current_hw_state is NULL
+        beq     vfp_reload_hw           @ then the hw state needs reloading
         VFPFSTMIA r4, r5                @ save the working registers
         VFPFMRX r5, FPSCR               @ current status
 #ifndef CONFIG_CPU_FEROCEON
@@ -110,13 +110,35 @@ ENTRY(vfp_support_entry)
 1:
 #endif
         stmia   r4, {r1, r5, r6, r8}    @ save FPEXC, FPSCR, FPINST, FPINST2
-                                        @ and point r4 at the word at the
-                                        @ start of the register dump
+vfp_reload_hw:
+
+#else
+        @ For SMP, if this thread does not own the hw context, then we
+        @ need to reload it.  No need to save the old state as on SMP,
+        @ we always save the state when we switch away from a thread.
+        bne     vfp_reload_hw
+
+        @ This thread has ownership of the current hardware context.
+        @ However, it may have been migrated to another CPU, in which
+        @ case the saved state is newer than the hardware context.
+        @ Check this by looking at the CPU number which the state was
+        @ last loaded onto.
+        ldr     ip, [r10, #VFP_CPU]
+        teq     ip, r11
+        beq     vfp_hw_state_valid
+
+vfp_reload_hw:
+        @ We're loading this threads state into the VFP hardware. Update
+        @ the CPU number which contains the most up to date VFP context.
+        str     r11, [r10, #VFP_CPU]
+
+        VFPFMXR FPEXC, r5               @ enable VFP, disable any pending
+                                        @ exceptions, so we can get at the
+                                        @ rest of it
 #endif
 
-no_old_VFP_process:
         DBGSTR1 "load state %p", r10
-        str     r10, [r3, r11, lsl #2]  @ update the last_VFP_context pointer
+        str     r10, [r3, r11, lsl #2]  @ update the vfp_current_hw_state pointer
                                         @ Load the saved state back into the VFP
         VFPFLDMIA r10, r5               @ reload the working registers while
                                         @ FPEXC is in a safe state
@@ -132,7 +154,8 @@ no_old_VFP_process:
 #endif
         VFPFMXR FPSCR, r5               @ restore status
 
-check_for_exception:
+@ The context stored in the VFP hardware is up to date with this thread
+vfp_hw_state_valid:
         tst     r1, #FPEXC_EX
         bne     process_exception       @ might as well handle the pending
                                         @ exception before retrying branch
@@ -207,8 +230,8 @@ ENTRY(vfp_save_state)
 ENDPROC(vfp_save_state)
 
         .align
-last_VFP_context_address:
-        .word   last_VFP_context
+vfp_current_hw_state_address:
+        .word   vfp_current_hw_state
 
         .macro  tbl_branch, base, tmp, shift
 #ifdef CONFIG_THUMB2_KERNEL