microblaze: Remove PER_CPU(KM) variable

There is a way howto remove Kernel Mode variable. It is easier
to parse UMS bit in MSR to find out if I come from kernel or user
space. Loading MSR content should be in one cycle and loading
PER_CPU variable depends on memory state.

Signed-off-by: Michal Simek <monstr@monstr.eu>

1 files changed, 20 insertions, 23 deletions

diff --git a/arch/microblaze/kernel/entry.S b/arch/microblaze/kernel/entry.S
index f5fe220954b0..9a98f70e4c30 100644
--- a/arch/microblaze/kernel/entry.S
+++ b/arch/microblaze/kernel/entry.S
@@ -275,9 +275,12 @@ C_ENTRY(_user_exception):
         addi    r14, r14, 4     /* return address is 4 byte after call */
         swi     r11, r0, TOPHYS(r0_ram + PTO + PT_R11); /* Save r11 */
 
-        lwi     r11, r0, TOPHYS(PER_CPU(KM));/* See if already in kernel mode.*/
-        beqi    r11, 1f;                /* Jump ahead if coming from user */
-/* Kernel-mode state save. */
+        mfs     r11, rmsr
+        nop
+        andi    r11, r11, MSR_UMS
+        bnei    r11, 1f
+
+/* Kernel-mode state save - kernel execve */
         lwi     r11, r0, TOPHYS(PER_CPU(ENTRY_SP)); /* Reload kernel stack-ptr*/
         tophys(r1,r11);
         swi     r11, r1, (PT_R1-PT_SIZE); /* Save original SP. */
@@ -307,8 +310,6 @@ C_ENTRY(_user_exception):
         swi     r0, r1, PTO+PT_MODE;                    /* Was in user-mode. */
         lwi     r11, r0, TOPHYS(PER_CPU(ENTRY_SP));
         swi     r11, r1, PTO+PT_R1;             /* Store user SP.  */
-        addi    r11, r0, 1;
-        swi     r11, r0, TOPHYS(PER_CPU(KM));   /* Now we're in kernel-mode.  */
 2:      lwi     CURRENT_TASK, r0, TOPHYS(PER_CPU(CURRENT_SAVE));
         /* Save away the syscall number.  */
         swi     r12, r1, PTO+PT_R0;
@@ -423,7 +424,6 @@ C_ENTRY(ret_from_trap):
 
 /* Finally, return to user state.  */
 1:
-        swi     r0, r0, PER_CPU(KM);    /* Now officially in user state. */
         swi     CURRENT_TASK, r0, PER_CPU(CURRENT_SAVE); /* save current */
         VM_OFF;
         tophys(r1,r1);
@@ -511,8 +511,10 @@ C_ENTRY(sys_rt_sigreturn_wrapper):
         enable_irq;                                                     \
         set_ee;                                                         \
         /* See if already in kernel mode.*/                             \
-        lwi     r11, r0, TOPHYS(PER_CPU(KM));                           \
-        beqi    r11, 1f;                /* Jump ahead if coming from user */\
+        mfs     r11, rmsr;                                              \
+        nop;                                                            \
+        andi    r11, r11, MSR_UMS;                                      \
+        bnei    r11, 1f;                                                \
         /* Kernel-mode state save.  */                                  \
         /* Reload kernel stack-ptr. */                                  \
         lwi     r11, r0, TOPHYS(PER_CPU(ENTRY_SP));                     \
@@ -544,8 +546,6 @@ C_ENTRY(sys_rt_sigreturn_wrapper):
         swi     r0, r1, PTO+PT_MODE; /* Was in user-mode.  */           \
         lwi     r11, r0, TOPHYS(PER_CPU(ENTRY_SP));                     \
         swi     r11, r1, PTO+PT_R1; /* Store user SP.  */               \
-        addi    r11, r0, 1;                                             \
-        swi     r11, r0, TOPHYS(PER_CPU(KM)); /* Now we're in kernel-mode.*/\
 2:      lwi     CURRENT_TASK, r0, TOPHYS(PER_CPU(CURRENT_SAVE));        \
         /* Save away the syscall number.  */                            \
         swi     r0, r1, PTO+PT_R0;                                      \
@@ -686,7 +686,7 @@ C_ENTRY(ret_from_exc):
         add     r6, r0, r0;             /* Arg 2: sigset_t *oldset */
 
 /* Finally, return to user state.  */
-1:      swi     r0, r0, PER_CPU(KM);    /* Now officially in user state. */
+1:
         swi     CURRENT_TASK, r0, PER_CPU(CURRENT_SAVE); /* save current */
         VM_OFF;
         tophys(r1,r1);
@@ -724,8 +724,10 @@ C_ENTRY(_interrupt):
         swi     r1, r0, TOPHYS(PER_CPU(ENTRY_SP))
         swi     r11, r0, TOPHYS(PER_CPU(R11_SAVE));
         /* MS: See if already in kernel mode. */
-        lwi     r11, r0, TOPHYS(PER_CPU(KM));
-        beqi    r11, 1f; /* MS: Jump ahead if coming from user */
+        mfs     r11, rmsr
+        nop
+        andi    r11, r11, MSR_UMS
+        bnei    r11, 1f
 
 /* Kernel-mode state save. */
         or      r11, r1, r0
@@ -761,10 +763,6 @@ C_ENTRY(_interrupt):
         swi     r0, r1, PTO + PT_MODE;
         lwi     r11, r0, TOPHYS(PER_CPU(ENTRY_SP));
         swi     r11, r1, PTO+PT_R1;
-        /* setup kernel mode to KM */
-        addi    r11, r0, 1;
-        swi     r11, r0, TOPHYS(PER_CPU(KM));
-
 2:
         lwi     CURRENT_TASK, r0, TOPHYS(PER_CPU(CURRENT_SAVE));
         swi     r0, r1, PTO + PT_R0;
@@ -803,7 +801,6 @@ ret_from_irq:
 no_intr_resched:
     /* Disable interrupts, we are now committed to the state restore */
         disable_irq
-        swi     r0, r0, PER_CPU(KM); /* MS: Now officially in user state. */
         swi     CURRENT_TASK, r0, PER_CPU(CURRENT_SAVE);
         VM_OFF;
         tophys(r1,r1);
@@ -858,8 +855,10 @@ C_ENTRY(_debug_exception):
         set_bip;        /*equalize initial state for all possible entries*/
         clear_eip;
         enable_irq;
-        lwi     r11, r0, TOPHYS(PER_CPU(KM));/* See if already in kernel mode.*/
-        beqi    r11, 1f;                /* Jump ahead if coming from user */
+        mfs     r11, rmsr
+        nop
+        andi    r11, r11, MSR_UMS
+        bnei    r11, 1f
         /* Kernel-mode state save.  */
         lwi     r11, r0, TOPHYS(PER_CPU(ENTRY_SP)); /* Reload kernel stack-ptr*/
         tophys(r1,r11);
@@ -887,8 +886,6 @@ C_ENTRY(_debug_exception):
         swi     r0, r1, PTO+PT_MODE; /* Was in user-mode.  */
         lwi     r11, r0, TOPHYS(PER_CPU(ENTRY_SP));
         swi     r11, r1, PTO+PT_R1; /* Store user SP.  */
-        addi    r11, r0, 1;
-        swi     r11, r0, TOPHYS(PER_CPU(KM));   /* Now we're in kernel-mode.  */
 2:      lwi     CURRENT_TASK, r0, TOPHYS(PER_CPU(CURRENT_SAVE));
         /* Save away the syscall number.  */
         swi     r0, r1, PTO+PT_R0;
@@ -944,7 +941,7 @@ dbtrap_call:	rtbd	r11, 0;
 
 
 /* Finally, return to user state.  */
-1:      swi     r0, r0, PER_CPU(KM);    /* Now officially in user state. */
+1:
         swi     CURRENT_TASK, r0, PER_CPU(CURRENT_SAVE); /* save current */
         VM_OFF;
         tophys(r1,r1);