From: Julien Grall <julien.grall@arm.com>
To: linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
kvmarm@lists.cs.columbia.edu
Cc: marc.zyngier@arm.com, catalin.marinas@arm.com,
will.deacon@arm.com, Russell King <linux@armlinux.org.uk>,
Julien Grall <julien.grall@arm.com>
Subject: [PATCH v3 13/15] arm/kvm: Introduce a new VMID allocator
Date: Wed, 24 Jul 2019 17:25:32 +0100 [thread overview]
Message-ID: <20190724162534.7390-14-julien.grall@arm.com> (raw)
In-Reply-To: <20190724162534.7390-1-julien.grall@arm.com>
A follow-up patch will replace the KVM VMID allocator with the arm64 ASID
allocator.
To avoid as much as possible duplication, the arm KVM code will directly
compile arch/arm64/lib/asid.c. The header is a verbatim to copy to
avoid breaking the assumption that architecture port has self-containers
headers.
Signed-off-by: Julien Grall <julien.grall@arm.com>
Cc: Russell King <linux@armlinux.org.uk>
---
I hit a warning when compiling the ASID code:
linux/arch/arm/kvm/../../arm64/lib/asid.c:17: warning: "ASID_MASK" redefined
#define ASID_MASK(info) (~GENMASK((info)->bits - 1, 0))
In file included from linux/include/linux/mm_types.h:18,
from linux/include/linux/mmzone.h:21,
from linux/include/linux/gfp.h:6,
from linux/include/linux/slab.h:15,
from linux/arch/arm/kvm/../../arm64/lib/asid.c:11:
linux/arch/arm/include/asm/mmu.h:26: note: this is the location of the previous definition
#define ASID_MASK ((~0ULL) << ASID_BITS)
I haven't yet resolved because I am not sure of the best way to go.
AFAICT ASID_MASK is only used in mm/context.c. So I am wondering whether
it would be acceptable to move the define.
Changes in v3:
- Resync arm32 with the arm64 header
Changes in v2:
- Re-use arm64/lib/asid.c rather than duplication the code.
---
arch/arm/include/asm/lib_asid.h | 79 +++++++++++++++++++++++++++++++++++++++++
arch/arm/kvm/Makefile | 1 +
2 files changed, 80 insertions(+)
create mode 100644 arch/arm/include/asm/lib_asid.h
diff --git a/arch/arm/include/asm/lib_asid.h b/arch/arm/include/asm/lib_asid.h
new file mode 100644
index 000000000000..e3233d37f5db
--- /dev/null
+++ b/arch/arm/include/asm/lib_asid.h
@@ -0,0 +1,79 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __ARM_LIB_ASID_H__
+#define __ARM_LIB_ASID_H__
+
+#include <linux/atomic.h>
+#include <linux/compiler.h>
+#include <linux/cpumask.h>
+#include <linux/percpu.h>
+#include <linux/spinlock.h>
+
+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 int ctxt_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(&active_asid(info, cpu));
+ if (old_active_asid &&
+ !((asid ^ atomic64_read(&info->generation)) >> info->bits) &&
+ atomic64_cmpxchg_relaxed(&active_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));
+
+void asid_allocator_free(struct asid_info *info);
+
+#endif /* __ARM_LIB_ASID_H__ */
diff --git a/arch/arm/kvm/Makefile b/arch/arm/kvm/Makefile
index 531e59f5be9c..6ab49bd84531 100644
--- a/arch/arm/kvm/Makefile
+++ b/arch/arm/kvm/Makefile
@@ -40,3 +40,4 @@ obj-y += $(KVM)/arm/vgic/vgic-its.o
obj-y += $(KVM)/arm/vgic/vgic-debug.o
obj-y += $(KVM)/irqchip.o
obj-y += $(KVM)/arm/arch_timer.o
+obj-y += ../../arm64/lib/asid.o
--
2.11.0
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next prev parent reply other threads:[~2019-07-24 16:26 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-24 16:25 [PATCH v3 00/15] kvm/arm: Align the VMID allocation with the arm64 ASID one Julien Grall
2019-07-24 16:25 ` [PATCH v3 01/15] arm64/mm: Introduce asid_info structure and move asid_generation/asid_map to it Julien Grall
2019-07-24 16:25 ` [PATCH v3 02/15] arm64/mm: Move active_asids and reserved_asids to asid_info Julien Grall
2019-07-24 16:25 ` [PATCH v3 03/15] arm64/mm: Move bits " Julien Grall
2019-07-24 16:25 ` [PATCH v3 04/15] arm64/mm: Move the variable lock and tlb_flush_pending " Julien Grall
2019-07-24 16:25 ` [PATCH v3 05/15] arm64/mm: Remove dependency on MM in new_context Julien Grall
2019-07-24 16:25 ` [PATCH v3 06/15] arm64/mm: Store the number of asid allocated per context Julien Grall
2019-07-24 16:25 ` [PATCH v3 07/15] arm64/mm: Introduce NUM_ASIDS Julien Grall
2019-07-24 16:25 ` [PATCH v3 08/15] arm64/mm: Split asid_inits in 2 parts Julien Grall
2019-07-24 16:25 ` [PATCH v3 09/15] arm64/mm: Split the function check_and_switch_context in 3 parts Julien Grall
2019-07-25 16:28 ` Catalin Marinas
2019-07-24 16:25 ` [PATCH v3 10/15] arm64/mm: Introduce a callback to flush the local context Julien Grall
2019-07-24 16:25 ` [PATCH v3 11/15] arm64: Move the ASID allocator code in a separate file Julien Grall
2019-07-24 16:25 ` [PATCH v3 12/15] arm64/lib: Add an helper to free memory allocated by the ASID allocator Julien Grall
2019-07-24 16:25 ` Julien Grall [this message]
2019-07-24 16:25 ` [PATCH v3 14/15] arch/arm64: Introduce a capability to tell whether 16-bit VMID is available Julien Grall
2019-07-24 16:25 ` [PATCH v3 15/15] kvm/arm: Align the VMID allocation with the arm64 ASID one Julien Grall
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