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authorTseng-Hui (Frank) Lin <thlin@linux.vnet.ibm.com>2011-05-02 20:43:04 +0000
committerBenjamin Herrenschmidt <benh@kernel.crashing.org>2011-05-04 15:19:26 +1000
commit851d2e2fe8dbcbe3afcad6fc4569c881d8ad4ce9 (patch)
tree94082e7751a66236febed1cf18a1f01a02084ae9 /arch/powerpc/mm
parenta32e252f7cdfb3675a4e50215cfac356ed8952c4 (diff)
downloadlinaro-lsk-851d2e2fe8dbcbe3afcad6fc4569c881d8ad4ce9.tar.gz
powerpc: Add Initiate Coprocessor Store Word (icswx) support
Icswx is a PowerPC instruction to send data to a co-processor. On Book-S processors the LPAR_ID and process ID (PID) of the owning process are registered in the window context of the co-processor at initialization time. When the icswx instruction is executed the L2 generates a cop-reg transaction on PowerBus. The transaction has no address and the processor does not perform an MMU access to authenticate the transaction. The co-processor compares the LPAR_ID and the PID included in the transaction and the LPAR_ID and PID held in the window context to determine if the process is authorized to generate the transaction. The OS needs to assign a 16-bit PID for the process. This cop-PID needs to be updated during context switch. The cop-PID needs to be destroyed when the context is destroyed. Signed-off-by: Sonny Rao <sonnyrao@linux.vnet.ibm.com> Signed-off-by: Tseng-Hui (Frank) Lin <thlin@linux.vnet.ibm.com> Signed-off-by: Anton Blanchard <anton@samba.org> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Diffstat (limited to 'arch/powerpc/mm')
-rw-r--r--arch/powerpc/mm/mmu_context_hash64.c211
1 files changed, 211 insertions, 0 deletions
diff --git a/arch/powerpc/mm/mmu_context_hash64.c b/arch/powerpc/mm/mmu_context_hash64.c
index c5859448a0a..c517815404c 100644
--- a/arch/powerpc/mm/mmu_context_hash64.c
+++ b/arch/powerpc/mm/mmu_context_hash64.c
@@ -20,9 +20,205 @@
#include <linux/idr.h>
#include <linux/module.h>
#include <linux/gfp.h>
+#include <linux/slab.h>
#include <asm/mmu_context.h>
+#ifdef CONFIG_PPC_ICSWX
+/*
+ * The processor and its L2 cache cause the icswx instruction to
+ * generate a COP_REQ transaction on PowerBus. The transaction has
+ * no address, and the processor does not perform an MMU access
+ * to authenticate the transaction. The command portion of the
+ * PowerBus COP_REQ transaction includes the LPAR_ID (LPID) and
+ * the coprocessor Process ID (PID), which the coprocessor compares
+ * to the authorized LPID and PID held in the coprocessor, to determine
+ * if the process is authorized to generate the transaction.
+ * The data of the COP_REQ transaction is 128-byte or less and is
+ * placed in cacheable memory on a 128-byte cache line boundary.
+ *
+ * The task to use a coprocessor should use use_cop() to allocate
+ * a coprocessor PID before executing icswx instruction. use_cop()
+ * also enables the coprocessor context switching. Drop_cop() is
+ * used to free the coprocessor PID.
+ *
+ * Example:
+ * Host Fabric Interface (HFI) is a PowerPC network coprocessor.
+ * Each HFI have multiple windows. Each HFI window serves as a
+ * network device sending to and receiving from HFI network.
+ * HFI immediate send function uses icswx instruction. The immediate
+ * send function allows small (single cache-line) packets be sent
+ * without using the regular HFI send FIFO and doorbell, which are
+ * much slower than immediate send.
+ *
+ * For each task intending to use HFI immediate send, the HFI driver
+ * calls use_cop() to obtain a coprocessor PID for the task.
+ * The HFI driver then allocate a free HFI window and save the
+ * coprocessor PID to the HFI window to allow the task to use the
+ * HFI window.
+ *
+ * The HFI driver repeatedly creates immediate send packets and
+ * issues icswx instruction to send data through the HFI window.
+ * The HFI compares the coprocessor PID in the CPU PID register
+ * to the PID held in the HFI window to determine if the transaction
+ * is allowed.
+ *
+ * When the task to release the HFI window, the HFI driver calls
+ * drop_cop() to release the coprocessor PID.
+ */
+
+#define COP_PID_NONE 0
+#define COP_PID_MIN (COP_PID_NONE + 1)
+#define COP_PID_MAX (0xFFFF)
+
+static DEFINE_SPINLOCK(mmu_context_acop_lock);
+static DEFINE_IDA(cop_ida);
+
+void switch_cop(struct mm_struct *next)
+{
+ mtspr(SPRN_PID, next->context.cop_pid);
+ mtspr(SPRN_ACOP, next->context.acop);
+}
+
+static int new_cop_pid(struct ida *ida, int min_id, int max_id,
+ spinlock_t *lock)
+{
+ int index;
+ int err;
+
+again:
+ if (!ida_pre_get(ida, GFP_KERNEL))
+ return -ENOMEM;
+
+ spin_lock(lock);
+ err = ida_get_new_above(ida, min_id, &index);
+ spin_unlock(lock);
+
+ if (err == -EAGAIN)
+ goto again;
+ else if (err)
+ return err;
+
+ if (index > max_id) {
+ spin_lock(lock);
+ ida_remove(ida, index);
+ spin_unlock(lock);
+ return -ENOMEM;
+ }
+
+ return index;
+}
+
+static void sync_cop(void *arg)
+{
+ struct mm_struct *mm = arg;
+
+ if (mm == current->active_mm)
+ switch_cop(current->active_mm);
+}
+
+/**
+ * Start using a coprocessor.
+ * @acop: mask of coprocessor to be used.
+ * @mm: The mm the coprocessor to associate with. Most likely current mm.
+ *
+ * Return a positive PID if successful. Negative errno otherwise.
+ * The returned PID will be fed to the coprocessor to determine if an
+ * icswx transaction is authenticated.
+ */
+int use_cop(unsigned long acop, struct mm_struct *mm)
+{
+ int ret;
+
+ if (!cpu_has_feature(CPU_FTR_ICSWX))
+ return -ENODEV;
+
+ if (!mm || !acop)
+ return -EINVAL;
+
+ /* We need to make sure mm_users doesn't change */
+ down_read(&mm->mmap_sem);
+ spin_lock(mm->context.cop_lockp);
+
+ if (mm->context.cop_pid == COP_PID_NONE) {
+ ret = new_cop_pid(&cop_ida, COP_PID_MIN, COP_PID_MAX,
+ &mmu_context_acop_lock);
+ if (ret < 0)
+ goto out;
+
+ mm->context.cop_pid = ret;
+ }
+ mm->context.acop |= acop;
+
+ sync_cop(mm);
+
+ /*
+ * If this is a threaded process then there might be other threads
+ * running. We need to send an IPI to force them to pick up any
+ * change in PID and ACOP.
+ */
+ if (atomic_read(&mm->mm_users) > 1)
+ smp_call_function(sync_cop, mm, 1);
+
+ ret = mm->context.cop_pid;
+
+out:
+ spin_unlock(mm->context.cop_lockp);
+ up_read(&mm->mmap_sem);
+
+ return ret;
+}
+EXPORT_SYMBOL_GPL(use_cop);
+
+/**
+ * Stop using a coprocessor.
+ * @acop: mask of coprocessor to be stopped.
+ * @mm: The mm the coprocessor associated with.
+ */
+void drop_cop(unsigned long acop, struct mm_struct *mm)
+{
+ int free_pid = COP_PID_NONE;
+
+ if (!cpu_has_feature(CPU_FTR_ICSWX))
+ return;
+
+ if (WARN_ON_ONCE(!mm))
+ return;
+
+ /* We need to make sure mm_users doesn't change */
+ down_read(&mm->mmap_sem);
+ spin_lock(mm->context.cop_lockp);
+
+ mm->context.acop &= ~acop;
+
+ if ((!mm->context.acop) && (mm->context.cop_pid != COP_PID_NONE)) {
+ free_pid = mm->context.cop_pid;
+ mm->context.cop_pid = COP_PID_NONE;
+ }
+
+ sync_cop(mm);
+
+ /*
+ * If this is a threaded process then there might be other threads
+ * running. We need to send an IPI to force them to pick up any
+ * change in PID and ACOP.
+ */
+ if (atomic_read(&mm->mm_users) > 1)
+ smp_call_function(sync_cop, mm, 1);
+
+ if (free_pid != COP_PID_NONE) {
+ spin_lock(&mmu_context_acop_lock);
+ ida_remove(&cop_ida, free_pid);
+ spin_unlock(&mmu_context_acop_lock);
+ }
+
+ spin_unlock(mm->context.cop_lockp);
+ up_read(&mm->mmap_sem);
+}
+EXPORT_SYMBOL_GPL(drop_cop);
+
+#endif /* CONFIG_PPC_ICSWX */
+
static DEFINE_SPINLOCK(mmu_context_lock);
static DEFINE_IDA(mmu_context_ida);
@@ -78,6 +274,16 @@ int init_new_context(struct task_struct *tsk, struct mm_struct *mm)
slice_set_user_psize(mm, mmu_virtual_psize);
subpage_prot_init_new_context(mm);
mm->context.id = index;
+#ifdef CONFIG_PPC_ICSWX
+ mm->context.cop_lockp = kmalloc(sizeof(spinlock_t), GFP_KERNEL);
+ if (!mm->context.cop_lockp) {
+ __destroy_context(index);
+ subpage_prot_free(mm);
+ mm->context.id = NO_CONTEXT;
+ return -ENOMEM;
+ }
+ spin_lock_init(mm->context.cop_lockp);
+#endif /* CONFIG_PPC_ICSWX */
return 0;
}
@@ -92,6 +298,11 @@ EXPORT_SYMBOL_GPL(__destroy_context);
void destroy_context(struct mm_struct *mm)
{
+#ifdef CONFIG_PPC_ICSWX
+ drop_cop(mm->context.acop, mm);
+ kfree(mm->context.cop_lockp);
+ mm->context.cop_lockp = NULL;
+#endif /* CONFIG_PPC_ICSWX */
__destroy_context(mm->context.id);
subpage_prot_free(mm);
mm->context.id = MMU_NO_CONTEXT;