We will want to re-use the ASID allocator in a separate context (e.g
allocating VMID). So move the code in a new file.
The function asid_check_context has been moved in the header as a static
inline function because we want to avoid add a branch when checking if the
ASID is still valid.
Signed-off-by: Julien Grall
---
This code will be used in the virt code for allocating VMID. I am not
entirely sure where to place it. Lib could potentially be a good place but I
am not entirely convinced the algo as it is could be used by other
architecture.
Looking at x86, it seems that it will not be possible to re-use because
the number of PCID (aka ASID) could be smaller than the number of CPUs.
See commit message 10af6235e0d327d42e1bad974385197817923dc1 "x86/mm:
Implement PCID based optimization: try to preserve old TLB entries using
PCI".
Changes in v2:
- Rename the header from asid.h to lib_asid.h
---
arch/arm64/include/asm/lib_asid.h | 77 +
arch/arm64/lib/Makefile | 2 +
arch/arm64/lib/asid.c | 185 ++
arch/arm64/mm/context.c | 235 +-
4 files changed, 267 insertions(+), 232 deletions(-)
create mode 100644 arch/arm64/include/asm/lib_asid.h
create mode 100644 arch/arm64/lib/asid.c
diff --git a/arch/arm64/include/asm/lib_asid.h
b/arch/arm64/include/asm/lib_asid.h
new file mode 100644
index ..c18e9eca500e
--- /dev/null
+++ b/arch/arm64/include/asm/lib_asid.h
@@ -0,0 +1,77 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __ASM_ASM_LIB_ASID_H
+#define __ASM_ASM_LIB_ASID_H
+
+#include
+#include
+#include
+#include
+#include
+
+struct asid_info
+{
+ atomic64_t generation;
+ unsigned long *map;
+ atomic64_t __percpu *active;
+ u64 __percpu*reserved;
+ u32 bits;
+ /* Lock protecting the structure */
+ raw_spinlock_t lock;
+ /* Which CPU requires context flush on next call */
+ cpumask_t flush_pending;
+ /* Number of ASID allocated by context (shift value) */
+ unsigned intctxt_shift;
+ /* Callback to locally flush the context. */
+ void(*flush_cpu_ctxt_cb)(void);
+};
+
+#define NUM_ASIDS(info)(1UL << ((info)->bits))
+#define NUM_CTXT_ASIDS(info) (NUM_ASIDS(info) >> (info)->ctxt_shift)
+
+#define active_asid(info, cpu) *per_cpu_ptr((info)->active, cpu)
+
+void asid_new_context(struct asid_info *info, atomic64_t *pasid,
+ unsigned int cpu);
+
+/*
+ * Check the ASID is still valid for the context. If not generate a new ASID.
+ *
+ * @pasid: Pointer to the current ASID batch
+ * @cpu: current CPU ID. Must have been acquired throught get_cpu()
+ */
+static inline void asid_check_context(struct asid_info *info,
+ atomic64_t *pasid, unsigned int cpu)
+{
+ u64 asid, old_active_asid;
+
+ asid = atomic64_read(pasid);
+
+ /*
+* The memory ordering here is subtle.
+* If our active_asid is non-zero and the ASID matches the current
+* generation, then we update the active_asid entry with a relaxed
+* cmpxchg. Racing with a concurrent rollover means that either:
+*
+* - We get a zero back from the cmpxchg and end up waiting on the
+* lock. Taking the lock synchronises with the rollover and so
+* we are forced to see the updated generation.
+*
+* - We get a valid ASID back from the cmpxchg, which means the
+* relaxed xchg in flush_context will treat us as reserved
+* because atomic RmWs are totally ordered for a given location.
+*/
+ old_active_asid = atomic64_read(_asid(info, cpu));
+ if (old_active_asid &&
+ !((asid ^ atomic64_read(>generation)) >> info->bits) &&
+ atomic64_cmpxchg_relaxed(_asid(info, cpu),
+old_active_asid, asid))
+ return;
+
+ asid_new_context(info, pasid, cpu);
+}
+
+int asid_allocator_init(struct asid_info *info,
+ u32 bits, unsigned int asid_per_ctxt,
+ void (*flush_cpu_ctxt_cb)(void));
+
+#endif
diff --git a/arch/arm64/lib/Makefile b/arch/arm64/lib/Makefile
index 33c2a4abda04..37169d541ab5 100644
--- a/arch/arm64/lib/Makefile
+++ b/arch/arm64/lib/Makefile
@@ -5,6 +5,8 @@ lib-y := clear_user.o delay.o copy_from_user.o
\
memcmp.o strcmp.o strncmp.o strlen.o strnlen.o \
strchr.o strrchr.o tishift.o
+lib-y += asid.o
+
ifeq ($(CONFIG_KERNEL_MODE_NEON), y)
obj-$(CONFIG_XOR_BLOCKS) += xor-neon.o
CFLAGS_REMOVE_xor-neon.o += -mgeneral-regs-only
diff --git a/arch/arm64/lib/asid.c b/arch/arm64/lib/asid.c
new file mode 100644
index ..7252e4fdd5e9
