[PATCH v2 1/6] cxl/mem: Drop DVSEC vs EFI Memory Map sanity check

From: Dan Williams <dan.j.williams@intel.com>
To: linux-cxl@vger.kernel.org
Cc: Davidlohr Bueso <dave@stgolabs.net>,
	ben.widawsky@intel.com, ira.weiny@intel.com,
	vishal.l.verma@intel.com, alison.schofield@intel.com
Subject: [PATCH v2 1/6] cxl/mem: Drop DVSEC vs EFI Memory Map sanity check
Date: Mon, 14 Mar 2022 18:22:22 -0700	[thread overview]
Message-ID: <164730734246.3806189.13995924771963139898.stgit@dwillia2-desk3.amr.corp.intel.com> (raw)
In-Reply-To: <164730733718.3806189.9721916820488234094.stgit@dwillia2-desk3.amr.corp.intel.com>

When the driver finds legacy DVSEC ranges active on a CXL Memory
Expander it indicates that platform firmware is not aware of, or is
deliberately disabling common CXL 2.0 operation. In this case Linux
generally has no choice, but to leave the device alone.

The driver attempts to validate that the DVSEC range is in the EFI
memory map. Remove that logic since there is no requirement that the
BIOS publish DVSEC ranges in the EFI Memory Map.

In the future the driver will want to permanently reserve this capacity
out of the available CFMWS capacity and hide it from
request_free_mem_region(), but it serves no purpose to warn about the
range not appearing in the EFI Memory Map.

Reviewed-by: Davidlohr Bueso <dave@stgolabs.net>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
 drivers/cxl/mem.c |   24 +-----------------------
 1 file changed, 1 insertion(+), 23 deletions(-)

diff --git a/drivers/cxl/mem.c b/drivers/cxl/mem.c
index 49a4b1c47299..cd4e8bba82aa 100644
--- a/drivers/cxl/mem.c
+++ b/drivers/cxl/mem.c
@@ -158,30 +158,8 @@ static int cxl_mem_probe(struct device *dev)
 	 * is no use in trying to manage those.
 	 */
 	if (!cxl_dvsec_decode_init(cxlds)) {
-		struct cxl_endpoint_dvsec_info *info = &cxlds->info;
-		int i;
-
-		/* */
-		for (i = 0; i < 2; i++) {
-			u64 base, size;
-
-			/*
-			 * Give a nice warning to the user that BIOS has really
-			 * botched things for them if it didn't place DVSEC
-			 * ranges in the memory map.
-			 */
-			base = info->dvsec_range[i].start;
-			size = range_len(&info->dvsec_range[i]);
-			if (size && !region_intersects(base, size,
-						       IORESOURCE_SYSTEM_RAM,
-						       IORES_DESC_NONE)) {
-				dev_err(dev,
-					"DVSEC range %#llx-%#llx must be reserved by BIOS, but isn't\n",
-					base, base + size - 1);
-			}
-		}
 		dev_err(dev,
-			"Active DVSEC range registers in use. Will not bind.\n");
+			"Legacy range registers configuration prevents HDM operation.\n");
 		return -EBUSY;
 	}
 

