cxl/cdat: Fix header sum value in CDAT checksum

The addition of the DCD support for CXL type-3 devices extended the CDAT
table large enough that the checksum being returned was incorrect.[1]

This was because the checksum value was using the header length field
rather than each of the 4 bytes of the length field.  This was
previously not seen because the length of the CDAT data was less than
256 thus resulting in an equivalent checksum value.

Properly calculate the checksum for the CDAT header.

[1] https://lore.kernel.org/all/20231116-fix-cdat-devm-free-v1-1-b148b40707d7@intel.com/

Fixes: aba578bdace5 ("hw/cxl/cdat: CXL CDAT Data Object Exchange implementation")
Cc: Huai-Cheng Kuo <hchkuo@avery-design.com.tw>
Signed-off-by: Ira Weiny <ira.weiny@intel.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Reviewed-by: Fan Ni <fan.ni@samsung.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Message-Id: <20240126120132.24248-5-Jonathan.Cameron@huawei.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
(cherry picked from commit 64fdad5e67587e88c2f1d8f294e89403856a4a31)
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>

diff --git a/hw/cxl/cxl-cdat.c b/hw/cxl/cxl-cdat.c
index 931693f02d4106bd5cfbe19d792ece25123a0b3c..0cde11854e4d3f7a343a38abe83143f7cb06364a 100644 (file)
--- a/hw/cxl/cxl-cdat.c
+++ b/hw/cxl/cxl-cdat.c
@@ -49,6 +49,7 @@ static void ct3_build_cdat(CDATObject *cdat, Error **errp)
     g_autofree CDATTableHeader *cdat_header = NULL;
     g_autofree CDATEntry *cdat_st = NULL;
     uint8_t sum = 0;
+    uint8_t *hdr_buf;
     int ent, i;
 
     /* Use default table if fopen == NULL */
@@ -94,8 +95,12 @@ static void ct3_build_cdat(CDATObject *cdat, Error **errp)
     /* For now, no runtime updates */
     cdat_header->sequence = 0;
     cdat_header->length += sizeof(CDATTableHeader);
-    sum += cdat_header->revision + cdat_header->sequence +
-        cdat_header->length;
+
+    hdr_buf = (uint8_t *)cdat_header;
+    for (i = 0; i < sizeof(*cdat_header); i++) {
+        sum += hdr_buf[i];
+    }
+
     /* Sum of all bytes including checksum must be 0 */
     cdat_header->checksum = ~sum + 1;