[PATCH v3 11/13] x86/xen: use lazy_mmu_state when context-switching

[Kevin Brodsky <kevin.brodsky@xxxxxxx>]

We currently set a TIF flag when scheduling out a task that is in
lazy MMU mode, in order to restore it when the task is scheduled
again.

The generic lazy_mmu layer now tracks whether a task is in lazy MMU
mode in task_struct::lazy_mmu_state. We can therefore check that
state when switching to the new task, instead of using a separate
TIF flag.

Signed-off-by: Kevin Brodsky <kevin.brodsky@xxxxxxx>
---
 arch/x86/include/asm/thread_info.h | 4 +---
 arch/x86/xen/enlighten_pv.c        | 3 +--
 2 files changed, 2 insertions(+), 5 deletions(-)

diff --git a/arch/x86/include/asm/thread_info.h 
b/arch/x86/include/asm/thread_info.h
index e71e0e8362ed..0067684afb5b 100644
--- a/arch/x86/include/asm/thread_info.h
+++ b/arch/x86/include/asm/thread_info.h
@@ -100,8 +100,7 @@ struct thread_info {
 #define TIF_FORCED_TF          24      /* true if TF in eflags artificially */
 #define TIF_SINGLESTEP         25      /* reenable singlestep on user return*/
 #define TIF_BLOCKSTEP          26      /* set when we want DEBUGCTLMSR_BTF */
-#define TIF_LAZY_MMU_UPDATES   27      /* task is updating the mmu lazily */
-#define TIF_ADDR32             28      /* 32-bit address space on 64 bits */
+#define TIF_ADDR32             27      /* 32-bit address space on 64 bits */
 
 #define _TIF_SSBD              BIT(TIF_SSBD)
 #define _TIF_SPEC_IB           BIT(TIF_SPEC_IB)
@@ -114,7 +113,6 @@ struct thread_info {
 #define _TIF_FORCED_TF         BIT(TIF_FORCED_TF)
 #define _TIF_BLOCKSTEP         BIT(TIF_BLOCKSTEP)
 #define _TIF_SINGLESTEP                BIT(TIF_SINGLESTEP)
-#define _TIF_LAZY_MMU_UPDATES  BIT(TIF_LAZY_MMU_UPDATES)
 #define _TIF_ADDR32            BIT(TIF_ADDR32)
 
 /* flags to check in __switch_to() */
diff --git a/arch/x86/xen/enlighten_pv.c b/arch/x86/xen/enlighten_pv.c
index 4806cc28d7ca..9fabe83e7546 100644
--- a/arch/x86/xen/enlighten_pv.c
+++ b/arch/x86/xen/enlighten_pv.c
@@ -426,7 +426,6 @@ static void xen_start_context_switch(struct task_struct 
*prev)
 
        if (this_cpu_read(xen_lazy_mode) == XEN_LAZY_MMU) {
                arch_leave_lazy_mmu_mode();
-               set_ti_thread_flag(task_thread_info(prev), 
TIF_LAZY_MMU_UPDATES);
        }
        enter_lazy(XEN_LAZY_CPU);
 }
@@ -437,7 +436,7 @@ static void xen_end_context_switch(struct task_struct *next)
 
        xen_mc_flush();
        leave_lazy(XEN_LAZY_CPU);
-       if (test_and_clear_ti_thread_flag(task_thread_info(next), 
TIF_LAZY_MMU_UPDATES))
+       if (next->lazy_mmu_state.enabled)
                arch_enter_lazy_mmu_mode();
 }
 
-- 
2.47.0