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Date: Thu, 16 Nov 2017 03:57:38 +0200
From: "Michael S. Tsirkin" <mst@...hat.com>
To: Marc-André Lureau <marcandre.lureau@...hat.com>
Cc: linux-kernel@...r.kernel.org, somlo@....edu, qemu-devel@...gnu.org
Subject: Re: [PATCH v6 5/5] fw_cfg: write vmcoreinfo details
On Mon, Nov 13, 2017 at 08:29:58PM +0100, Marc-André Lureau wrote:
> 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 <marcandre.lureau@...hat.com>
> Reviewed-by: Gabriel Somlo <somlo@....edu>
> ---
> 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 <somlo@....edu>");
> 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;
It's a small bit of data - you can just keep it in a global variable,
this way failures won't be an issue.
> +
> + /* 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
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