[PATCH v7 06/11] cxl: Validate HDM ranges before CXL reset

[Srirangan Madhavan]

Before reset, collect enabled cached HDM decoder ranges, reserve them with
request_mem_region(), and invalidate CPU caches. This rejects reset while
affected CXL memory is busy and keeps the validation stable through reset.

Signed-off-by: Srirangan Madhavan <smadhavan@xxxxxxxxxx>
---
 drivers/cxl/core/reset.c | 239 ++++++++++++++++++++++++++++++++++++++-
 1 file changed, 238 insertions(+), 1 deletion(-)

diff --git a/drivers/cxl/core/reset.c b/drivers/cxl/core/reset.c
index fdfcc9e825e0..786d1060e40d 100644
--- a/drivers/cxl/core/reset.c
+++ b/drivers/cxl/core/reset.c
@@ -10,6 +10,8 @@
 #include <linux/iommu.h>
 #include <linux/jiffies.h>
 #include <linux/kernel.h>
+#include <linux/list.h>
+#include <linux/memregion.h>
 #include <linux/pci.h>
 #include <linux/slab.h>
 
@@ -336,6 +338,230 @@ static const u32 cxl_reset_timeout_ms[] = {
 #define CXL_CACHE_WBI_TIMEOUT_US 100000
 #define CXL_CACHE_WBI_POLL_US 100
 
+struct cxl_hdm_range {
+	struct list_head list;
+	struct pci_dev *pdev;
+	struct range hpa_range;
+	struct resource *res;
+};
+
+struct cxl_hdm_range_context {
+	struct list_head ranges;
+};
+
+static void cxl_hdm_range_context_init(struct cxl_hdm_range_context *ctx)
+{
+	INIT_LIST_HEAD(&ctx->ranges);
+}
+
+static void cxl_hdm_range_context_destroy(struct cxl_hdm_range_context *ctx)
+{
+	struct cxl_hdm_range *range, *next;
+
+	list_for_each_entry_safe(range, next, &ctx->ranges, list) {
+		list_del(&range->list);
+		if (range->res)
+			release_mem_region(range->hpa_range.start,
+					   resource_size(range->res));
+		kfree(range);
+	}
+}
+
+static int cxl_hdm_range_add(struct cxl_hdm_range_context *ctx,
+			     struct pci_dev *pdev, const struct range *hpa_range)
+{
+	struct cxl_hdm_range *range;
+
+	if (hpa_range->end < hpa_range->start)
+		return -EINVAL;
+
+	list_for_each_entry(range, &ctx->ranges, list)
+		if (range->hpa_range.start == hpa_range->start &&
+		    range->hpa_range.end == hpa_range->end)
+			return 0;
+
+	range = kzalloc_obj(*range);
+	if (!range)
+		return -ENOMEM;
+
+	range->pdev = pdev;
+	range->hpa_range = *hpa_range;
+	list_add_tail(&range->list, &ctx->ranges);
+
+	return 0;
+}
+
+static int cxl_hdm_ranges_collect(struct cxl_hdm_range_context *ctx,
+				  struct pci_dev *pdev)
+{
+	struct cxl_hdm_info *info = READ_ONCE(pdev->hdm);
+	int rc;
+
+	if (!info) {
+		pci_err(pdev, "CXL HDM decoder state unavailable\n");
+		return -ENXIO;
+	}
+
+	for (int i = 0; i < info->decoder_count; i++) {
+		struct cxl_decoder_settings *settings = &info->settings[i];
+
+		if (!(settings->flags & CXL_DECODER_F_ENABLE))
+			continue;
+
+		if (settings->flags & CXL_DECODER_F_NORMALIZED_ADDRESSING) {
+			pci_err(pdev,
+				"CXL reset does not support normalized address decoders\n");
+			return -EOPNOTSUPP;
+		}
+
+		rc = cxl_hdm_range_add(ctx, pdev, &settings->hpa_range);
+		if (rc)
+			return rc;
+	}
+
+	return 0;
+}
+
+static int cxl_hdm_range_len(struct pci_dev *pdev,
+			     const struct range *hpa_range, u64 *len)
+{
+	if (sizeof(resource_size_t) < sizeof(hpa_range->start) &&
+	    (hpa_range->start > (resource_size_t)~0ULL ||
+	     hpa_range->end > (resource_size_t)~0ULL)) {
+		pci_err(pdev,
+			"CXL reset range [%#llx-%#llx] exceeds resource address size\n",
+			hpa_range->start, hpa_range->end);
+		return -EOVERFLOW;
+	}
+
+	if (hpa_range->end < hpa_range->start)
+		return -EINVAL;
+
+	if (!hpa_range->start && hpa_range->end == U64_MAX) {
+		pci_err(pdev,
+			"CXL reset range [%#llx-%#llx] exceeds resource size\n",
+			hpa_range->start, hpa_range->end);
+		return -EOVERFLOW;
+	}
+
+	*len = range_len(hpa_range);
+	if (sizeof(resource_size_t) < sizeof(*len) &&
+	    *len > (resource_size_t)~0ULL) {
+		pci_err(pdev,
+			"CXL reset range [%#llx-%#llx] exceeds resource size\n",
+			hpa_range->start, hpa_range->end);
+		return -EOVERFLOW;
+	}
+
+	if (sizeof(size_t) < sizeof(*len) && *len > SIZE_MAX) {
+		pci_err(pdev,
+			"CXL reset range [%#llx-%#llx] exceeds cache flush size\n",
+			hpa_range->start, hpa_range->end);
+		return -EOVERFLOW;
+	}
+
+	return 0;
+}
+
+static int cxl_hdm_range_request(struct cxl_hdm_range *range)
+{
+	struct pci_dev *pdev = range->pdev;
+	const struct range *hpa_range = &range->hpa_range;
+	u64 len;
+	int rc;
+
+	rc = cxl_hdm_range_len(pdev, hpa_range, &len);
+	if (rc)
+		return rc;
+
+	range->res = request_mem_region(hpa_range->start, len, "cxl_reset");
+	if (!range->res) {
+		pci_err(pdev,
+			"cannot reset while CXL memory range is busy [%#llx-%#llx]\n",
+			hpa_range->start, hpa_range->end);
+		return -EBUSY;
+	}
+
+	return 0;
+}
+
+static int cxl_hdm_ranges_request(struct cxl_hdm_range_context *ctx)
+{
+	struct cxl_hdm_range *range;
+	int rc;
+
+	lockdep_assert_held_write(&cxl_rwsem.region);
+
+	list_for_each_entry(range, &ctx->ranges, list) {
+		rc = cxl_hdm_range_request(range);
+		if (rc)
+			return rc;
+	}
+
+	return 0;
+}
+
+static int cxl_hdm_range_flush_cache(struct cxl_hdm_range *range)
+{
+	struct pci_dev *pdev = range->pdev;
+	const struct range *hpa_range = &range->hpa_range;
+	u64 len;
+	int rc;
+
+	rc = cxl_hdm_range_len(pdev, hpa_range, &len);
+	if (rc)
+		return rc;
+
+	rc = cpu_cache_invalidate_memregion(hpa_range->start, len);
+	if (rc)
+		pci_err(pdev,
+			"failed to invalidate CPU cache [%#llx-%#llx]: %d\n",
+			hpa_range->start, hpa_range->end, rc);
+
+	return rc;
+}
+
+static int cxl_hdm_ranges_flush_cpu_caches(struct cxl_hdm_range_context *ctx,
+					   struct pci_dev *pdev)
+{
+	struct cxl_hdm_range *range;
+	int rc;
+
+	if (list_empty(&ctx->ranges))
+		return 0;
+
+	if (!cpu_cache_has_invalidate_memregion()) {
+		pci_err(pdev, "failed to synchronize CPU cache state\n");
+		return -ENXIO;
+	}
+
+	list_for_each_entry(range, &ctx->ranges, list) {
+		rc = cxl_hdm_range_flush_cache(range);
+		if (rc)
+			return rc;
+	}
+
+	return 0;
+}
+
+static int cxl_hdm_ranges_prepare(struct cxl_hdm_range_context *ctx,
+				  struct pci_dev *pdev)
+{
+	int rc;
+
+	lockdep_assert_held_write(&cxl_rwsem.region);
+
+	rc = cxl_hdm_ranges_collect(ctx, pdev);
+	if (rc)
+		return rc;
+
+	rc = cxl_hdm_ranges_request(ctx);
+	if (rc)
+		return rc;
+
+	return cxl_hdm_ranges_flush_cpu_caches(ctx, pdev);
+}
+
 static int cxl_reset_dvsec(struct pci_dev *pdev)
 {
 	int dvsec, rc;
@@ -528,7 +754,9 @@ static int cxl_reset_execute(struct pci_dev *pdev, int dvsec)
 
 int cxl_reset_function(struct pci_dev *pdev, bool probe)
 {
+	struct cxl_hdm_range_context range_ctx;
 	int dvsec;
+	int rc;
 
 	dvsec = cxl_reset_dvsec(pdev);
 	if (dvsec < 0)
@@ -537,5 +765,14 @@ int cxl_reset_function(struct pci_dev *pdev, bool probe)
 	if (probe)
 		return 0;
 
-	return cxl_reset_execute(pdev, dvsec);
+	cxl_hdm_range_context_init(&range_ctx);
+
+	scoped_guard(rwsem_write, &cxl_rwsem.region) {
+		rc = cxl_hdm_ranges_prepare(&range_ctx, pdev);
+		if (!rc)
+			rc = cxl_reset_execute(pdev, dvsec);
+	}
+
+	cxl_hdm_range_context_destroy(&range_ctx);
+	return rc;
 }
-- 
2.43.0