cxl/mem: Fix register block offset calculation

The "Register Offset Low" register of a "DVSEC Register Locator"
contains the 64K aligned offset for the registers along with the BAR
indicator and an id. The implementation was treating the "Register Block
Offset Low" field a value rather than as a pre-aligned component of the
64-bit offset. So, just mask, don't mask and shift (FIELD_GET).

The user visible result of this bug is that the driver fails to bind to
the device after none of the required blocks are found.

This was missed earlier because the primary development done in the QEMU
environment only uses 0 offsets, i.e. 0 shifted is still 0.

Fixes: fc78f3260985 ("cxl/mem: Find device capabilities")
Reported-by: Vishal Verma <vishal.l.verma@intel.com>
Signed-off-by: Ben Widawsky <ben.widawsky@intel.com>
Link: https://lore.kernel.org/r/20210415232610.603273-1-ben.widawsky@intel.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

diff --git a/drivers/cxl/mem.c b/drivers/cxl/mem.c
index e3003f49b3296d0ee8cea49cf2ca057a3e0d692c..1b5078311f7d6dcdc2fd6a8ab1745b2eea01d887 100644 (file)
--- a/drivers/cxl/mem.c
+++ b/drivers/cxl/mem.c
@@ -998,7 +998,7 @@ static struct cxl_mem *cxl_mem_create(struct pci_dev *pdev, u32 reg_lo,
                return NULL;
        }
 
-       offset = ((u64)reg_hi << 32) | FIELD_GET(CXL_REGLOC_ADDR_MASK, reg_lo);
+       offset = ((u64)reg_hi << 32) | (reg_lo & CXL_REGLOC_ADDR_MASK);
        bar = FIELD_GET(CXL_REGLOC_BIR_MASK, reg_lo);
 
        /* Basic sanity check that BAR is big enough */