platform/x86: dcdbas: Check SMBIOS for protected buffer address

Add support for a new method for BIOS to provide the address and length
of the protected SMI communication buffer, via SMBIOS OEM strings.

Signed-off-by: Stuart Hayes <stuart.w.hayes@gmail.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

diff --git a/drivers/platform/x86/dcdbas.c b/drivers/platform/x86/dcdbas.c
index 84f4cc8..d513a59 100644 (file)
--- a/drivers/platform/x86/dcdbas.c
+++ b/drivers/platform/x86/dcdbas.c
@@ -15,6 +15,7 @@
 #include <linux/platform_device.h>
 #include <linux/acpi.h>
 #include <linux/dma-mapping.h>
+#include <linux/dmi.h>
 #include <linux/errno.h>
 #include <linux/cpu.h>
 #include <linux/gfp.h>
@@ -34,7 +35,7 @@
 #include "dcdbas.h"
 
 #define DRIVER_NAME            "dcdbas"
-#define DRIVER_VERSION         "5.6.0-3.3"
+#define DRIVER_VERSION         "5.6.0-3.4"
 #define DRIVER_DESCRIPTION     "Dell Systems Management Base Driver"
 
 static struct platform_device *dcdbas_pdev;
@@ -45,7 +46,7 @@ static unsigned long smi_data_buf_size;
 static unsigned long max_smi_data_buf_size = MAX_SMI_DATA_BUF_SIZE;
 static u32 smi_data_buf_phys_addr;
 static DEFINE_MUTEX(smi_data_lock);
-static u8 *eps_buffer;
+static u8 *bios_buffer;
 
 static unsigned int host_control_action;
 static unsigned int host_control_smi_type;
@@ -518,8 +519,10 @@ static inline struct smm_eps_table *check_eps_table(u8 *addr)
 
 static int dcdbas_check_wsmt(void)
 {
+       const struct dmi_device *dev = NULL;
        struct acpi_table_wsmt *wsmt = NULL;
        struct smm_eps_table *eps = NULL;
+       u64 bios_buf_paddr;
        u64 remap_size;
        u8 *addr;
 
@@ -532,6 +535,17 @@ static int dcdbas_check_wsmt(void)
            !(wsmt->protection_flags & ACPI_WSMT_COMM_BUFFER_NESTED_PTR_PROTECTION))
                return 0;
 
+       /*
+        * BIOS could provide the address/size of the protected buffer
+        * in an SMBIOS string or in an EPS structure in 0xFxxxx.
+        */
+
+       /* Check SMBIOS for buffer address */
+       while ((dev = dmi_find_device(DMI_DEV_TYPE_OEM_STRING, NULL, dev)))
+               if (sscanf(dev->name, "30[%16llx;%8llx]", &bios_buf_paddr,
+                   &remap_size) == 2)
+                       goto remap;
+
        /* Scan for EPS (entry point structure) */
        for (addr = (u8 *)__va(0xf0000);
             addr < (u8 *)__va(0x100000 - sizeof(struct smm_eps_table));
@@ -542,34 +556,37 @@ static int dcdbas_check_wsmt(void)
        }
 
        if (!eps) {
-               dev_dbg(&dcdbas_pdev->dev, "found WSMT, but no EPS found\n");
+               dev_dbg(&dcdbas_pdev->dev, "found WSMT, but no firmware buffer found\n");
                return -ENODEV;
        }
+       bios_buf_paddr = eps->smm_comm_buff_addr;
+       remap_size = eps->num_of_4k_pages * PAGE_SIZE;
 
+remap:
        /*
         * Get physical address of buffer and map to virtual address.
         * Table gives size in 4K pages, regardless of actual system page size.
         */
-       if (upper_32_bits(eps->smm_comm_buff_addr + 8)) {
-               dev_warn(&dcdbas_pdev->dev, "found WSMT, but EPS buffer address is above 4GB\n");
+       if (upper_32_bits(bios_buf_paddr + 8)) {
+               dev_warn(&dcdbas_pdev->dev, "found WSMT, but buffer address is above 4GB\n");
                return -EINVAL;
        }
        /*
         * Limit remap size to MAX_SMI_DATA_BUF_SIZE + 8 (since the first 8
         * bytes are used for a semaphore, not the data buffer itself).
         */
-       remap_size = eps->num_of_4k_pages * PAGE_SIZE;
        if (remap_size > MAX_SMI_DATA_BUF_SIZE + 8)
                remap_size = MAX_SMI_DATA_BUF_SIZE + 8;
-       eps_buffer = memremap(eps->smm_comm_buff_addr, remap_size, MEMREMAP_WB);
-       if (!eps_buffer) {
-               dev_warn(&dcdbas_pdev->dev, "found WSMT, but failed to map EPS buffer\n");
+
+       bios_buffer = memremap(bios_buf_paddr, remap_size, MEMREMAP_WB);
+       if (!bios_buffer) {
+               dev_warn(&dcdbas_pdev->dev, "found WSMT, but failed to map buffer\n");
                return -ENOMEM;
        }
 
        /* First 8 bytes is for a semaphore, not part of the smi_data_buf */
-       smi_data_buf_phys_addr = eps->smm_comm_buff_addr + 8;
-       smi_data_buf = eps_buffer + 8;
+       smi_data_buf_phys_addr = bios_buf_paddr + 8;
+       smi_data_buf = bios_buffer + 8;
        smi_data_buf_size = remap_size - 8;
        max_smi_data_buf_size = smi_data_buf_size;
        wsmt_enabled = true;
@@ -736,8 +753,8 @@ static void __exit dcdbas_exit(void)
         */
        if (dcdbas_pdev)
                smi_data_buf_free();
-       if (eps_buffer)
-               memunmap(eps_buffer);
+       if (bios_buffer)
+               memunmap(bios_buffer);
        platform_device_unregister(dcdbas_pdev_reg);
        platform_driver_unregister(&dcdbas_driver);
 }