[Qemu-devel] [PATCH v6 5/5] fw_cfg: write vmcoreinfo details

[Marc-André Lureau]

If the "etc/vmcoreinfo" fw_cfg file is present and we are not running
the kdump kernel, write the addr/size of the vmcoreinfo ELF note.

Signed-off-by: Marc-André Lureau <address@hidden>
Reviewed-by: Gabriel Somlo <address@hidden>
---
 drivers/firmware/qemu_fw_cfg.c | 87 +++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 86 insertions(+), 1 deletion(-)

diff --git a/drivers/firmware/qemu_fw_cfg.c b/drivers/firmware/qemu_fw_cfg.c
index 2ac4cd869fe6..7a70e7a549f6 100644
--- a/drivers/firmware/qemu_fw_cfg.c
+++ b/drivers/firmware/qemu_fw_cfg.c
@@ -35,6 +35,8 @@
 #include <linux/ioport.h>
 #include <linux/delay.h>
 #include <linux/dma-mapping.h>
+#include <linux/crash_core.h>
+#include <linux/crash_dump.h>
 
 MODULE_AUTHOR("Gabriel L. Somlo <address@hidden>");
 MODULE_DESCRIPTION("QEMU fw_cfg sysfs support");
@@ -59,6 +61,8 @@ MODULE_LICENSE("GPL");
 /* fw_cfg "file name" is up to 56 characters (including terminating nul) */
 #define FW_CFG_MAX_FILE_PATH 56
 
+#define VMCOREINFO_FORMAT_ELF 0x1
+
 /* platform device for dma mapping */
 static struct device *dev;
 
@@ -127,7 +131,8 @@ static ssize_t fw_cfg_dma_transfer(void *address, u32 
length, u32 control)
        dma_addr_t dma;
        ssize_t ret = length;
        enum dma_data_direction dir =
-               (control & FW_CFG_DMA_CTL_READ ? DMA_FROM_DEVICE : 0);
+               (control & FW_CFG_DMA_CTL_READ ? DMA_FROM_DEVICE : 0) |
+               (control & FW_CFG_DMA_CTL_WRITE ? DMA_TO_DEVICE : 0);
 
        if (address && length) {
                dma_addr = dma_map_single(dev, address, length, dir);
@@ -225,6 +230,48 @@ static ssize_t fw_cfg_read_blob(u16 key,
        return ret;
 }
 
+#ifdef CONFIG_CRASH_CORE
+/* write chunk of given fw_cfg blob (caller responsible for sanity-check) */
+static ssize_t fw_cfg_write_blob(u16 key,
+                                void *buf, loff_t pos, size_t count)
+{
+       u32 glk = -1U;
+       acpi_status status;
+       ssize_t ret = count;
+
+       /* If we have ACPI, ensure mutual exclusion against any potential
+        * device access by the firmware, e.g. via AML methods:
+        */
+       status = acpi_acquire_global_lock(ACPI_WAIT_FOREVER, &glk);
+       if (ACPI_FAILURE(status) && status != AE_NOT_CONFIGURED) {
+               /* Should never get here */
+               WARN(1, "%s: Failed to lock ACPI!\n", __func__);
+               memset(buf, 0, count);
+               return -EINVAL;
+       }
+
+       mutex_lock(&fw_cfg_dev_lock);
+       if (pos == 0) {
+               ret = fw_cfg_dma_transfer(buf, count, key << 16
+                                         | FW_CFG_DMA_CTL_SELECT
+                                         | FW_CFG_DMA_CTL_WRITE);
+       } else {
+               iowrite16(fw_cfg_sel_endianness(key), fw_cfg_reg_ctrl);
+               ret = fw_cfg_dma_transfer(NULL, pos, FW_CFG_DMA_CTL_SKIP);
+               if (ret < 0)
+                       goto end;
+               ret = fw_cfg_dma_transfer(buf, count, FW_CFG_DMA_CTL_WRITE);
+       }
+
+end:
+       mutex_unlock(&fw_cfg_dev_lock);
+
+       acpi_release_global_lock(glk);
+
+       return ret;
+}
+#endif /* CONFIG_CRASH_CORE */
+
 /* clean up fw_cfg device i/o */
 static void fw_cfg_io_cleanup(void)
 {
@@ -343,6 +390,37 @@ struct fw_cfg_sysfs_entry {
        struct list_head list;
 };
 
+#ifdef CONFIG_CRASH_CORE
+static ssize_t write_vmcoreinfo(const struct fw_cfg_file *f)
+{
+       struct vmci {
+               __le16 host_format;
+               __le16 guest_format;
+               __le32 size;
+               __le64 paddr;
+       } __packed;
+       struct vmci *data;
+       ssize_t ret;
+
+       data = kmalloc(sizeof(struct vmci), GFP_KERNEL | GFP_DMA);
+       if (!data)
+               return -ENOMEM;
+
+       /* spare ourself reading host format support for now since we
+        * don't know what else to format - host may ignore ours
+        */
+       *data = (struct vmci) {
+               .guest_format = cpu_to_le16(VMCOREINFO_FORMAT_ELF),
+               .size = cpu_to_le32(VMCOREINFO_NOTE_SIZE),
+               .paddr = cpu_to_le64(paddr_vmcoreinfo_note())
+       };
+       ret = fw_cfg_write_blob(f->select, data, 0, sizeof(struct vmci));
+
+       kfree(data);
+       return ret;
+}
+#endif /* CONFIG_CRASH_CORE */
+
 /* get fw_cfg_sysfs_entry from kobject member */
 static inline struct fw_cfg_sysfs_entry *to_entry(struct kobject *kobj)
 {
@@ -582,6 +660,13 @@ static int fw_cfg_register_file(const struct fw_cfg_file 
*f)
        int err;
        struct fw_cfg_sysfs_entry *entry;
 
+#ifdef CONFIG_CRASH_CORE
+       if (strcmp(f->name, "etc/vmcoreinfo") == 0 && !is_kdump_kernel()) {
+               if (write_vmcoreinfo(f) < 0)
+                       pr_warn("fw_cfg: failed to write vmcoreinfo");
+       }
+#endif
+
        /* allocate new entry */
        entry = kzalloc(sizeof(*entry), GFP_KERNEL);
        if (!entry)
-- 
2.15.0.125.g8f49766d64