[PATCH v4 5/9] powerpc/vas: Map paste address only if window is active

[Haren Myneni]

The paste address mapping is done with mmap() after the window is
opened with ioctl. If the window is closed by OS in the hypervisor
due to DLPAR after this mmap(), the paste instruction returns
failure until the OS reopens this window again. But before mmap(),
DLPAR core removal can happen which causes the corresponding
window in-active. So if the window is not active, return mmap()
failure with -EACCES and expects the user space reissue mmap()
when the window is active or open a new window when the credit
is available.

Signed-off-by: Haren Myneni <haren at linux.ibm.com>
---
 arch/powerpc/platforms/book3s/vas-api.c | 20 +++++++++++++++++++-
 1 file changed, 19 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/platforms/book3s/vas-api.c b/arch/powerpc/platforms/book3s/vas-api.c
index f3e421511ea6..eb4489b2b46b 100644
--- a/arch/powerpc/platforms/book3s/vas-api.c
+++ b/arch/powerpc/platforms/book3s/vas-api.c
@@ -496,10 +496,26 @@ 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.
+	 */
+	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;
@@ -519,6 +535,8 @@ static int coproc_mmap(struct file *fp, struct vm_area_struct *vma)
 	txwin->task_ref.vma = vma;
 	vma->vm_ops = &vas_vm_ops;
 
+out:
+	mutex_unlock(&txwin->task_ref.mmap_mutex);
 	return rc;
 }
 
-- 
2.27.0