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Diffstat (limited to 'arch/powerpc/platforms/book3s/vas-api.c')
-rw-r--r--arch/powerpc/platforms/book3s/vas-api.c145
1 files changed, 144 insertions, 1 deletions
diff --git a/arch/powerpc/platforms/book3s/vas-api.c b/arch/powerpc/platforms/book3s/vas-api.c
index 4d82c92ddd52..f9a1615b74da 100644
--- a/arch/powerpc/platforms/book3s/vas-api.c
+++ b/arch/powerpc/platforms/book3s/vas-api.c
@@ -316,6 +316,7 @@ static int coproc_ioc_tx_win_open(struct file *fp, unsigned long arg)
return PTR_ERR(txwin);
}
+ mutex_init(&txwin->task_ref.mmap_mutex);
cp_inst->txwin = txwin;
return 0;
@@ -350,6 +351,124 @@ static int coproc_release(struct inode *inode, struct file *fp)
return 0;
}
+/*
+ * If the executed instruction that caused the fault was a paste, then
+ * clear regs CR0[EQ], advance NIP, and return 0. Else return error code.
+ */
+static int do_fail_paste(void)
+{
+ struct pt_regs *regs = current->thread.regs;
+ u32 instword;
+
+ if (WARN_ON_ONCE(!regs))
+ return -EINVAL;
+
+ if (WARN_ON_ONCE(!user_mode(regs)))
+ return -EINVAL;
+
+ /*
+ * If we couldn't translate the instruction, the driver should
+ * return success without handling the fault, it will be retried
+ * or the instruction fetch will fault.
+ */
+ if (get_user(instword, (u32 __user *)(regs->nip)))
+ return -EAGAIN;
+
+ /*
+ * Not a paste instruction, driver may fail the fault.
+ */
+ if ((instword & PPC_INST_PASTE_MASK) != PPC_INST_PASTE)
+ return -ENOENT;
+
+ regs->ccr &= ~0xe0000000; /* Clear CR0[0-2] to fail paste */
+ regs_add_return_ip(regs, 4); /* Emulate the paste */
+
+ return 0;
+}
+
+/*
+ * This fault handler is invoked when the core generates page fault on
+ * the paste address. Happens if the kernel closes window in hypervisor
+ * (on pseries) due to lost credit or the paste address is not mapped.
+ */
+static vm_fault_t vas_mmap_fault(struct vm_fault *vmf)
+{
+ struct vm_area_struct *vma = vmf->vma;
+ struct file *fp = vma->vm_file;
+ struct coproc_instance *cp_inst = fp->private_data;
+ struct vas_window *txwin;
+ vm_fault_t fault;
+ u64 paste_addr;
+ int ret;
+
+ /*
+ * window is not opened. Shouldn't expect this error.
+ */
+ if (!cp_inst || !cp_inst->txwin) {
+ pr_err("%s(): Unexpected fault on paste address with TX window closed\n",
+ __func__);
+ return VM_FAULT_SIGBUS;
+ }
+
+ txwin = cp_inst->txwin;
+ /*
+ * When the LPAR lost credits due to core removal or during
+ * migration, invalidate the existing mapping for the current
+ * paste addresses and set windows in-active (zap_page_range in
+ * reconfig_close_windows()).
+ * New mapping will be done later after migration or new credits
+ * available. So continue to receive faults if the user space
+ * issue NX request.
+ */
+ if (txwin->task_ref.vma != vmf->vma) {
+ pr_err("%s(): No previous mapping with paste address\n",
+ __func__);
+ return VM_FAULT_SIGBUS;
+ }
+
+ mutex_lock(&txwin->task_ref.mmap_mutex);
+ /*
+ * The window may be inactive due to lost credit (Ex: core
+ * removal with DLPAR). If the window is active again when
+ * the credit is available, map the new paste address at the
+ * the window virtual address.
+ */
+ if (txwin->status == VAS_WIN_ACTIVE) {
+ paste_addr = cp_inst->coproc->vops->paste_addr(txwin);
+ if (paste_addr) {
+ fault = vmf_insert_pfn(vma, vma->vm_start,
+ (paste_addr >> PAGE_SHIFT));
+ mutex_unlock(&txwin->task_ref.mmap_mutex);
+ return fault;
+ }
+ }
+ mutex_unlock(&txwin->task_ref.mmap_mutex);
+
+ /*
+ * Received this fault due to closing the actual window.
+ * It can happen during migration or lost credits.
+ * Since no mapping, return the paste instruction failure
+ * to the user space.
+ */
+ ret = do_fail_paste();
+ /*
+ * The user space can retry several times until success (needed
+ * for migration) or should fallback to SW compression or
+ * manage with the existing open windows if available.
+ * Looking at sysfs interface, it can determine whether these
+ * failures are coming during migration or core removal:
+ * nr_used_credits > nr_total_credits when lost credits
+ */
+ if (!ret || (ret == -EAGAIN))
+ return VM_FAULT_NOPAGE;
+
+ return VM_FAULT_SIGBUS;
+}
+
+static const struct vm_operations_struct vas_vm_ops = {
+ .fault = vas_mmap_fault,
+};
+
static int coproc_mmap(struct file *fp, struct vm_area_struct *vma)
{
struct coproc_instance *cp_inst = fp->private_data;
@@ -378,10 +497,29 @@ static int coproc_mmap(struct file *fp, struct vm_area_struct *vma)
return -EACCES;
}
+ /*
+ * The initial mmap is done after the window is opened
+ * with ioctl. But before mmap(), this window can be closed in
+ * the hypervisor due to lost credit (core removal on pseries).
+ * So if the window is not active, return mmap() failure with
+ * -EACCES and expects the user space reissue mmap() when it
+ * is active again or open new window when the credit is available.
+ * mmap_mutex protects the paste address mmap() with DLPAR
+ * close/open event and allows mmap() only when the window is
+ * active.
+ */
+ mutex_lock(&txwin->task_ref.mmap_mutex);
+ if (txwin->status != VAS_WIN_ACTIVE) {
+ pr_err("%s(): Window is not active\n", __func__);
+ rc = -EACCES;
+ goto out;
+ }
+
paste_addr = cp_inst->coproc->vops->paste_addr(txwin);
if (!paste_addr) {
pr_err("%s(): Window paste address failed\n", __func__);
- return -EINVAL;
+ rc = -EINVAL;
+ goto out;
}
pfn = paste_addr >> PAGE_SHIFT;
@@ -398,6 +536,11 @@ static int coproc_mmap(struct file *fp, struct vm_area_struct *vma)
pr_devel("%s(): paste addr %llx at %lx, rc %d\n", __func__,
paste_addr, vma->vm_start, rc);
+ txwin->task_ref.vma = vma;
+ vma->vm_ops = &vas_vm_ops;
+
+out:
+ mutex_unlock(&txwin->task_ref.mmap_mutex);
return rc;
}