x86/xen: use lazy_mmu_state when context-switching

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.

Link: https://lkml.kernel.org/r/20251215150323.2218608-14-kevin.brodsky@arm.com
Signed-off-by: Kevin Brodsky <kevin.brodsky@arm.com>
Acked-by: David Hildenbrand (Red Hat) <david@kernel.org>
Reviewed-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Yeoreum Yun <yeoreum.yun@arm.com>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Andreas Larsson <andreas@gaisler.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Borislav Betkov <bp@alien8.de>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: David Hildenbrand <david@redhat.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jann Horn <jannh@google.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Madhavan Srinivasan <maddy@linux.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Thomas Gleinxer <tglx@linutronix.de>
Cc: Venkat Rao Bagalkote <venkat88@linux.ibm.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/arch/x86/include/asm/thread_info.h b/arch/x86/include/asm/thread_info.h
index e71e0e8362ed8ead7acd7915b278a651e177244e..0067684afb5b79f4733097ade9e55bc582ceaa06 100644 (file)
--- 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 b74ff8bc7f2a8df2ff8d11bb72a01f4ee7acfeec..ae52436a741f0a4167ed59eb4d8cda7961e490ed 100644 (file)
--- 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 (__task_lazy_mmu_mode_active(next))
                arch_enter_lazy_mmu_mode();
 }