3 files changed, 20 insertions, 2 deletions

diff --git a/drivers/misc/cxl/context.c b/drivers/misc/cxl/context.c
index 615842115848..941fda04aa9a 100644
--- a/drivers/misc/cxl/context.c
+++ b/drivers/misc/cxl/context.c
@@ -126,6 +126,18 @@ static int cxl_mmap_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
 	if (ctx->status != STARTED) {
 		mutex_unlock(&ctx->status_mutex);
 		pr_devel("%s: Context not started, failing problem state access\n", __func__);
+		if (ctx->mmio_err_ff) {
+			if (!ctx->ff_page) {
+				ctx->ff_page = alloc_page(GFP_USER);
+				if (!ctx->ff_page)
+					return VM_FAULT_OOM;
+				memset(page_address(ctx->ff_page), 0xff, PAGE_SIZE);
+			}
+			get_page(ctx->ff_page);
+			vmf->page = ctx->ff_page;
+			vma->vm_page_prot = pgprot_cached(vma->vm_page_prot);
+			return 0;
+		}
 		return VM_FAULT_SIGBUS;
 	}
 
@@ -257,6 +269,8 @@ static void reclaim_ctx(struct rcu_head *rcu)
 	struct cxl_context *ctx = container_of(rcu, struct cxl_context, rcu);
 
 	free_page((u64)ctx->sstp);
+	if (ctx->ff_page)
+		__free_page(ctx->ff_page);
 	ctx->sstp = NULL;
 
 	kfree(ctx);
diff --git a/drivers/misc/cxl/cxl.h b/drivers/misc/cxl/cxl.h
index 6f5386653dae..e7af256f60c5 100644
--- a/drivers/misc/cxl/cxl.h
+++ b/drivers/misc/cxl/cxl.h
@@ -34,7 +34,7 @@ extern uint cxl_verbose;
  * Bump version each time a user API change is made, whether it is
  * backwards compatible ot not.
  */
-#define CXL_API_VERSION 1
+#define CXL_API_VERSION 2
 #define CXL_API_VERSION_COMPATIBLE 1
 
 /*
@@ -418,6 +418,8 @@ struct cxl_context {
 	/* Used to unmap any mmaps when force detaching */
 	struct address_space *mapping;
 	struct mutex mapping_lock;
+	struct page *ff_page;
+	bool mmio_err_ff;
 
 	spinlock_t sste_lock; /* Protects segment table entries */
 	struct cxl_sste *sstp;
diff --git a/drivers/misc/cxl/file.c b/drivers/misc/cxl/file.c
index 57bdb473749f..a30bf285b5bd 100644
--- a/drivers/misc/cxl/file.c
+++ b/drivers/misc/cxl/file.c
@@ -184,6 +184,8 @@ static long afu_ioctl_start_work(struct cxl_context *ctx,
 	if (work.flags & CXL_START_WORK_AMR)
 		amr = work.amr & mfspr(SPRN_UAMOR);
 
+	ctx->mmio_err_ff = !!(work.flags & CXL_START_WORK_ERR_FF);
+
 	/*
 	 * We grab the PID here and not in the file open to allow for the case
 	 * where a process (master, some daemon, etc) has opened the chardev on
@@ -538,7 +540,7 @@ int __init cxl_file_init(void)
 	 * If these change we really need to update API.  Either change some
 	 * flags or update API version number CXL_API_VERSION.
 	 */
-	BUILD_BUG_ON(CXL_API_VERSION != 1);
+	BUILD_BUG_ON(CXL_API_VERSION != 2);
 	BUILD_BUG_ON(sizeof(struct cxl_ioctl_start_work) != 64);
 	BUILD_BUG_ON(sizeof(struct cxl_event_header) != 8);
 	BUILD_BUG_ON(sizeof(struct cxl_event_afu_interrupt) != 8);