linux-kernel - [PATCH v2 3/4] fw_cfg: write vmcoreinfo details

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Message-Id: <20170919115814.14724-4-marcandre.lureau@redhat.com>
Date:   Tue, 19 Sep 2017 13:58:13 +0200
From:   marcandre.lureau@...hat.com
To:     linux-kernel@...r.kernel.org
Cc:     somlo@....edu, qemu-devel@...gnu.org, mst@...hat.com,
        Marc-André Lureau <marcandre.lureau@...hat.com>
Subject: [PATCH v2 3/4] fw_cfg: write vmcoreinfo details

From: Marc-André Lureau <marcandre.lureau@...hat.com>

If the "etc/vmcoreinfo" file is present, write the addr/size of the
vmcoreinfo ELF note.

Signed-off-by: Marc-André Lureau <marcandre.lureau@...hat.com>
---
 drivers/firmware/qemu_fw_cfg.c | 80 +++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 79 insertions(+), 1 deletion(-)

diff --git a/drivers/firmware/qemu_fw_cfg.c b/drivers/firmware/qemu_fw_cfg.c
index a0e24fdf3ae5..26152bfc7805 100644
--- a/drivers/firmware/qemu_fw_cfg.c
+++ b/drivers/firmware/qemu_fw_cfg.c
@@ -34,6 +34,7 @@
 #include <linux/io.h>
 #include <linux/ioport.h>
 #include <linux/dma-mapping.h>
+#include <linux/crash_core.h>
 
 MODULE_AUTHOR("Gabriel L. Somlo <somlo@....edu>");
 MODULE_DESCRIPTION("QEMU fw_cfg sysfs support");
@@ -57,6 +58,8 @@ 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;
 
@@ -107,7 +110,8 @@ 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);
@@ -203,6 +207,46 @@ static ssize_t fw_cfg_read_blob(u16 key,
 	return ret;
 }
 
+/* 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 -EBUSY;
+	}
+
+	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(0, 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;
+}
+
 /* clean up fw_cfg device i/o */
 static void fw_cfg_io_cleanup(void)
 {
@@ -321,6 +365,35 @@ struct fw_cfg_sysfs_entry {
 	struct list_head list;
 };
 
+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;
+}
+
 /* get fw_cfg_sysfs_entry from kobject member */
 static inline struct fw_cfg_sysfs_entry *to_entry(struct kobject *kobj)
 {
@@ -560,6 +633,11 @@ static int fw_cfg_register_file(const struct fw_cfg_file *f)
 	int err;
 	struct fw_cfg_sysfs_entry *entry;
 
+	if (strcmp(f->name, "etc/vmcoreinfo") == 0) {
+		if (write_vmcoreinfo(f) < 0)
+			pr_warn("fw_cfg: failed to write vmcoreinfo");
+	}
+
 	/* allocate new entry */
 	entry = kzalloc(sizeof(*entry), GFP_KERNEL);
 	if (!entry)
-- 
2.14.1.146.gd35faa819