lkml.org 
[lkml]   [2018]   [Jul]   [3]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    Subject[PATCH v5] dcdbas: Add support for WSMT ACPI table
    From
    Date

    If the WSMT ACPI table is present and indicates that a fixed communication
    buffer should be used, use the firmware-specified buffer instead of
    allocating a buffer in memory for communications between the dcdbas driver
    and firmare.

    Signed-off-by: Stuart Hayes <stuart.w.hayes@gmail.com>
    ---
    v2 Bumped driver version to 5.6.0-3.3
    v3 Removed dependency on ACPI in Kconfig
    Moved the added #include to be in alphabetical order
    Added comments in smi_request_store()
    Simplified checksum code
    Changed loop searching 0xf0000 to be more readable
    Reworked calculation of remap_size & smi_data_buf_size
    v4 Fixed comment that starts with "Calling Interface SMI"
    Fixed formatting of first "if" statement in dcdbas_check_wsmt()
    v5 Reworked comment that starts with "Calling Interface SMI"
    Changed EPS scanning loop to check every 16 bytes


    drivers/firmware/dcdbas.c | 123 +++++++++++++++++++++++++++++++++++++++++++---
    drivers/firmware/dcdbas.h | 10 ++++
    2 files changed, 127 insertions(+), 6 deletions(-)

    diff --git a/drivers/firmware/dcdbas.c b/drivers/firmware/dcdbas.c
    index 0bdea60c65dd..ae28e48ff7dc 100644
    --- a/drivers/firmware/dcdbas.c
    +++ b/drivers/firmware/dcdbas.c
    @@ -21,6 +21,7 @@
    */

    #include <linux/platform_device.h>
    +#include <linux/acpi.h>
    #include <linux/dma-mapping.h>
    #include <linux/errno.h>
    #include <linux/cpu.h>
    @@ -41,7 +42,7 @@
    #include "dcdbas.h"

    #define DRIVER_NAME "dcdbas"
    -#define DRIVER_VERSION "5.6.0-3.2"
    +#define DRIVER_VERSION "5.6.0-3.3"
    #define DRIVER_DESCRIPTION "Dell Systems Management Base Driver"

    static struct platform_device *dcdbas_pdev;
    @@ -49,19 +50,23 @@ static struct platform_device *dcdbas_pdev;
    static u8 *smi_data_buf;
    static dma_addr_t smi_data_buf_handle;
    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 unsigned int host_control_action;
    static unsigned int host_control_smi_type;
    static unsigned int host_control_on_shutdown;

    +static bool wsmt_enabled;
    +
    /**
    * smi_data_buf_free: free SMI data buffer
    */
    static void smi_data_buf_free(void)
    {
    - if (!smi_data_buf)
    + if (!smi_data_buf || wsmt_enabled)
    return;

    dev_dbg(&dcdbas_pdev->dev, "%s: phys: %x size: %lu\n",
    @@ -86,7 +91,7 @@ static int smi_data_buf_realloc(unsigned long size)
    if (smi_data_buf_size >= size)
    return 0;

    - if (size > MAX_SMI_DATA_BUF_SIZE)
    + if (size > max_smi_data_buf_size)
    return -EINVAL;

    /* new buffer is needed */
    @@ -169,7 +174,7 @@ static ssize_t smi_data_write(struct file *filp, struct kobject *kobj,
    {
    ssize_t ret;

    - if ((pos + count) > MAX_SMI_DATA_BUF_SIZE)
    + if ((pos + count) > max_smi_data_buf_size)
    return -EINVAL;

    mutex_lock(&smi_data_lock);
    @@ -322,8 +327,20 @@ static ssize_t smi_request_store(struct device *dev,
    ret = count;
    break;
    case 1:
    - /* Calling Interface SMI */
    - smi_cmd->ebx = (u32) virt_to_phys(smi_cmd->command_buffer);
    + /*
    + * Calling Interface SMI
    + *
    + * Provide physical address of command buffer field within
    + * the struct smi_cmd to BIOS.
    + *
    + * Because the address that smi_cmd (smi_data_buf) points to
    + * will be from memremap() of a non-memory address if WSMT
    + * is present, we can't use virt_to_phys() on smi_cmd, so
    + * we have to use the physical address that was saved when
    + * the virtual address for smi_cmd was received.
    + */
    + smi_cmd->ebx = smi_data_buf_phys_addr +
    + offsetof(struct smi_cmd, command_buffer);
    ret = dcdbas_smi_request(smi_cmd);
    if (!ret)
    ret = count;
    @@ -482,6 +499,93 @@ static void dcdbas_host_control(void)
    }
    }

    +/* WSMT */
    +
    +static u8 checksum(u8 *buffer, u8 length)
    +{
    + u8 sum = 0;
    + u8 *end = buffer + length;
    +
    + while (buffer < end)
    + sum += *buffer++;
    + return sum;
    +}
    +
    +static inline struct smm_eps_table *check_eps_table(u8 *addr)
    +{
    + struct smm_eps_table *eps = (struct smm_eps_table *)addr;
    +
    + if (strncmp(eps->smm_comm_buff_anchor, SMM_EPS_SIG, 4) != 0)
    + return NULL;
    +
    + if (checksum(addr, eps->length) != 0)
    + return NULL;
    +
    + return eps;
    +}
    +
    +static int dcdbas_check_wsmt(void)
    +{
    + struct acpi_table_wsmt *wsmt = NULL;
    + struct smm_eps_table *eps = NULL;
    + u64 remap_size;
    + u8 *addr;
    +
    + acpi_get_table(ACPI_SIG_WSMT, 0, (struct acpi_table_header **)&wsmt);
    + if (!wsmt)
    + return 0;
    +
    + /* Check if WSMT ACPI table shows that protection is enabled */
    + if (!(wsmt->protection_flags & ACPI_WSMT_FIXED_COMM_BUFFERS) ||
    + !(wsmt->protection_flags & ACPI_WSMT_COMM_BUFFER_NESTED_PTR_PROTECTION))
    + return 0;
    +
    + /* Scan for EPS (entry point structure) */
    + for (addr = (u8 *)__va(0xf0000);
    + addr < (u8 *)__va(0x100000 - sizeof(struct smm_eps_table));
    + addr += 16) {
    + eps = check_eps_table(addr);
    + if (eps)
    + break;
    + }
    +
    + if (!eps) {
    + dev_dbg(&dcdbas_pdev->dev, "found WSMT, but no EPS found\n");
    + return -ENODEV;
    + }
    +
    + /*
    + * 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");
    + 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");
    + 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_size = remap_size - 8;
    + max_smi_data_buf_size = smi_data_buf_size;
    + wsmt_enabled = true;
    + dev_info(&dcdbas_pdev->dev,
    + "WSMT found, using firmware-provided SMI buffer.\n");
    + return 1;
    +}
    +
    /**
    * dcdbas_reboot_notify: handle reboot notification for host control
    */
    @@ -548,6 +652,11 @@ static int dcdbas_probe(struct platform_device *dev)

    dcdbas_pdev = dev;

    + /* Check if ACPI WSMT table specifies protected SMI buffer address */
    + error = dcdbas_check_wsmt();
    + if (error < 0)
    + return error;
    +
    /*
    * BIOS SMI calls require buffer addresses be in 32-bit address space.
    * This is done by setting the DMA mask below.
    @@ -635,6 +744,8 @@ static void __exit dcdbas_exit(void)
    */
    if (dcdbas_pdev)
    smi_data_buf_free();
    + if (eps_buffer)
    + memunmap(eps_buffer);
    platform_device_unregister(dcdbas_pdev_reg);
    platform_driver_unregister(&dcdbas_driver);
    }
    diff --git a/drivers/firmware/dcdbas.h b/drivers/firmware/dcdbas.h
    index ca3cb0a54ab6..52729a494b00 100644
    --- a/drivers/firmware/dcdbas.h
    +++ b/drivers/firmware/dcdbas.h
    @@ -53,6 +53,7 @@
    #define EXPIRED_TIMER (0)

    #define SMI_CMD_MAGIC (0x534D4931)
    +#define SMM_EPS_SIG "$SCB"

    #define DCDBAS_DEV_ATTR_RW(_name) \
    DEVICE_ATTR(_name,0600,_name##_show,_name##_store);
    @@ -103,5 +104,14 @@ struct apm_cmd {

    int dcdbas_smi_request(struct smi_cmd *smi_cmd);

    +struct smm_eps_table {
    + char smm_comm_buff_anchor[4];
    + u8 length;
    + u8 checksum;
    + u8 version;
    + u64 smm_comm_buff_addr;
    + u64 num_of_4k_pages;
    +} __packed;
    +
    #endif /* _DCDBAS_H_ */

    --
    2.14.2
    \
     
     \ /
      Last update: 2018-07-03 18:21    [W:5.473 / U:0.412 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site