[PATCH] ocxl: Allow contexts to be attached with a NULL mm

[Alastair D'Silva]

From: Alastair D'Silva <alast...@d-silva.org>

If an OpenCAPI context is to be used directly by a kernel driver, there
may not be a suitable mm to use.

The patch makes the mm parameter to ocxl_context_attach optional.

Signed-off-by: Alastair D'Silva <alast...@d-silva.org>
---
 drivers/misc/ocxl/context.c |  9 ++++++---
 drivers/misc/ocxl/link.c    | 12 ++++++++----
 2 files changed, 14 insertions(+), 7 deletions(-)

diff --git a/drivers/misc/ocxl/context.c b/drivers/misc/ocxl/context.c
index bab9c9364184..994563a078eb 100644
--- a/drivers/misc/ocxl/context.c
+++ b/drivers/misc/ocxl/context.c
@@ -69,6 +69,7 @@ static void xsl_fault_error(void *data, u64 addr, u64 dsisr)
 int ocxl_context_attach(struct ocxl_context *ctx, u64 amr, struct mm_struct 
*mm)
 {
        int rc;
+       unsigned long pidr = 0;
 
        // Locks both status & tidr
        mutex_lock(&ctx->status_mutex);
@@ -77,9 +78,11 @@ int ocxl_context_attach(struct ocxl_context *ctx, u64 amr, 
struct mm_struct *mm)
                goto out;
        }
 
-       rc = ocxl_link_add_pe(ctx->afu->fn->link, ctx->pasid,
-                       mm->context.id, ctx->tidr, amr, mm,
-                       xsl_fault_error, ctx);
+       if (mm)
+               pidr = mm->context.id;
+
+       rc = ocxl_link_add_pe(ctx->afu->fn->link, ctx->pasid, pidr, ctx->tidr,
+                             amr, mm, xsl_fault_error, ctx);
        if (rc)
                goto out;
 
diff --git a/drivers/misc/ocxl/link.c b/drivers/misc/ocxl/link.c
index cce5b0d64505..43542f124807 100644
--- a/drivers/misc/ocxl/link.c
+++ b/drivers/misc/ocxl/link.c
@@ -523,7 +523,8 @@ int ocxl_link_add_pe(void *link_handle, int pasid, u32 
pidr, u32 tidr,
        pe->amr = cpu_to_be64(amr);
        pe->software_state = cpu_to_be32(SPA_PE_VALID);
 
-       mm_context_add_copro(mm);
+       if (mm)
+               mm_context_add_copro(mm);
        /*
         * Barrier is to make sure PE is visible in the SPA before it
         * is used by the device. It also helps with the global TLBI
@@ -546,7 +547,8 @@ int ocxl_link_add_pe(void *link_handle, int pasid, u32 
pidr, u32 tidr,
         * have a reference on mm_users. Incrementing mm_count solves
         * the problem.
         */
-       mmgrab(mm);
+       if (mm)
+               mmgrab(mm);
        trace_ocxl_context_add(current->pid, spa->spa_mem, pasid, pidr, tidr);
 unlock:
        mutex_unlock(&spa->spa_lock);
@@ -652,8 +654,10 @@ int ocxl_link_remove_pe(void *link_handle, int pasid)
        if (!pe_data) {
                WARN(1, "Couldn't find pe data when removing PE\n");
        } else {
-               mm_context_remove_copro(pe_data->mm);
-               mmdrop(pe_data->mm);
+               if (pe_data->mm) {
+                       mm_context_remove_copro(pe_data->mm);
+                       mmdrop(pe_data->mm);
+               }
                kfree_rcu(pe_data, rcu);
        }
 unlock:
-- 
2.21.0