cxl: Allow the kernel to trust that an image won't change on PERST.

Provide a kernel API and a sysfs entry which allow a user to specify
that when a card is PERSTed, it's image will stay the same, allowing
it to participate in EEH.

cxl_reset is used to reflash the card. In that case, we cannot safely
assert that the image will not change. Therefore, disallow cxl_reset
if the flag is set.

Signed-off-by: Daniel Axtens <dja@axtens.net>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

4 files changed, 41 insertions, 0 deletions

diff --git a/drivers/misc/cxl/api.c b/drivers/misc/cxl/api.c
index 729e0851167d..6a768a9ad22f 100644
--- a/drivers/misc/cxl/api.c
+++ b/drivers/misc/cxl/api.c
@@ -327,3 +327,10 @@ int cxl_afu_reset(struct cxl_context *ctx)
         return cxl_afu_check_and_enable(afu);
 }
 EXPORT_SYMBOL_GPL(cxl_afu_reset);
+
+void cxl_perst_reloads_same_image(struct cxl_afu *afu,
+                                  bool perst_reloads_same_image)
+{
+        afu->adapter->perst_same_image = perst_reloads_same_image;
+}
+EXPORT_SYMBOL_GPL(cxl_perst_reloads_same_image);
diff --git a/drivers/misc/cxl/cxl.h b/drivers/misc/cxl/cxl.h
index d540542f9931..cda02412b01e 100644
--- a/drivers/misc/cxl/cxl.h
+++ b/drivers/misc/cxl/cxl.h
@@ -493,6 +493,7 @@ struct cxl {
         bool user_image_loaded;
         bool perst_loads_image;
         bool perst_select_user;
+        bool perst_same_image;
 };
 
 int cxl_alloc_one_irq(struct cxl *adapter);
diff --git a/drivers/misc/cxl/pci.c b/drivers/misc/cxl/pci.c
index 2b61cb1ee62c..bfbd6478c0c5 100644
--- a/drivers/misc/cxl/pci.c
+++ b/drivers/misc/cxl/pci.c
@@ -878,6 +878,12 @@ int cxl_reset(struct cxl *adapter)
         int i;
         u32 val;
 
+        if (adapter->perst_same_image) {
+                dev_warn(&dev->dev,
+                         "cxl: refusing to reset/reflash when perst_reloads_same_image is set.\n");
+                return -EINVAL;
+        }
+
         dev_info(&dev->dev, "CXL reset\n");
 
         /* pcie_warm_reset requests a fundamental pci reset which includes a
@@ -1151,6 +1157,7 @@ static struct cxl *cxl_init_adapter(struct pci_dev *dev)
          * configure/reconfigure
          */
         adapter->perst_loads_image = true;
+        adapter->perst_same_image = false;
 
         rc = cxl_configure_adapter(adapter, dev);
         if (rc) {
diff --git a/drivers/misc/cxl/sysfs.c b/drivers/misc/cxl/sysfs.c
index 31f38bc71a3d..6619cf1f6e1f 100644
--- a/drivers/misc/cxl/sysfs.c
+++ b/drivers/misc/cxl/sysfs.c
@@ -112,12 +112,38 @@ static ssize_t load_image_on_perst_store(struct device *device,
         return count;
 }
 
+static ssize_t perst_reloads_same_image_show(struct device *device,
+                                 struct device_attribute *attr,
+                                 char *buf)
+{
+        struct cxl *adapter = to_cxl_adapter(device);
+
+        return scnprintf(buf, PAGE_SIZE, "%i\n", adapter->perst_same_image);
+}
+
+static ssize_t perst_reloads_same_image_store(struct device *device,
+                                 struct device_attribute *attr,
+                                 const char *buf, size_t count)
+{
+        struct cxl *adapter = to_cxl_adapter(device);
+        int rc;
+        int val;
+
+        rc = sscanf(buf, "%i", &val);
+        if ((rc != 1) || !(val == 1 || val == 0))
+                return -EINVAL;
+
+        adapter->perst_same_image = (val == 1 ? true : false);
+        return count;
+}
+
 static struct device_attribute adapter_attrs[] = {
         __ATTR_RO(caia_version),
         __ATTR_RO(psl_revision),
         __ATTR_RO(base_image),
         __ATTR_RO(image_loaded),
         __ATTR_RW(load_image_on_perst),
+        __ATTR_RW(perst_reloads_same_image),
         __ATTR(reset, S_IWUSR, NULL, reset_adapter_store),
 };