On Wed, Feb 07, 2018 at 02:35:24AM +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.
>
> The DMA operation is expected to run synchronously with today qemu,
> but the specification states that it may become async, so we run
> "control" field check in a loop for eventual changes.
>
> Signed-off-by: Marc-André Lureau <marcandre.lur...@redhat.com>
> ---
> drivers/firmware/qemu_fw_cfg.c | 157
> ++++++++++++++++++++++++++++++++++++++++-
> 1 file changed, 154 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/firmware/qemu_fw_cfg.c b/drivers/firmware/qemu_fw_cfg.c
> index 740df0df2260..fd576ba7b337 100644
> --- a/drivers/firmware/qemu_fw_cfg.c
> +++ b/drivers/firmware/qemu_fw_cfg.c
> @@ -33,6 +33,9 @@
> #include <linux/slab.h>
> #include <linux/io.h>
> #include <linux/ioport.h>
> +#include <linux/delay.h>
> +#include <linux/crash_dump.h>
> +#include <linux/crash_core.h>
>
> MODULE_AUTHOR("Gabriel L. Somlo <so...@cmu.edu>");
> MODULE_DESCRIPTION("QEMU fw_cfg sysfs support");
> @@ -43,12 +46,24 @@ MODULE_LICENSE("GPL");
> #define FW_CFG_ID 0x01
> #define FW_CFG_FILE_DIR 0x19
>
> +#define FW_CFG_VERSION_DMA 0x02
> +#define FW_CFG_DMA_CTL_ERROR 0x01
> +#define FW_CFG_DMA_CTL_READ 0x02
> +#define FW_CFG_DMA_CTL_SKIP 0x04
> +#define FW_CFG_DMA_CTL_SELECT 0x08
> +#define FW_CFG_DMA_CTL_WRITE 0x10
> +
> /* size in bytes of fw_cfg signature */
> #define FW_CFG_SIG_SIZE 4
>
> /* fw_cfg "file name" is up to 56 characters (including terminating nul) */
> #define FW_CFG_MAX_FILE_PATH 56
>
> +#define VMCOREINFO_FORMAT_ELF 0x1
How about exporting interface parts in include/uapi/linux/ ?
QEMU can import it from there then.
This is what virtio does.
> +
> +/* fw_cfg revision attribute, in /sys/firmware/qemu_fw_cfg top-level dir. */
> +static u32 fw_cfg_rev;
> +
> /* fw_cfg file directory entry type */
> struct fw_cfg_file {
> u32 size;
> @@ -57,6 +72,12 @@ struct fw_cfg_file {
> char name[FW_CFG_MAX_FILE_PATH];
> };
>
> +struct fw_cfg_dma {
> + u32 control;
> + u32 length;
> + u64 address;
> +} __packed;
> +
you can drop __packed here - it's always aligned properly.
> /* fw_cfg device i/o register addresses */
> static bool fw_cfg_is_mmio;
> static phys_addr_t fw_cfg_p_base;
> @@ -75,6 +96,59 @@ static inline u16 fw_cfg_sel_endianness(u16 key)
> return fw_cfg_is_mmio ? cpu_to_be16(key) : cpu_to_le16(key);
> }
>
> +static inline bool fw_cfg_dma_enabled(void)
> +{
> + return fw_cfg_rev & FW_CFG_VERSION_DMA && fw_cfg_reg_dma;
Why do you use () with == below but not with && here?
> +}
> +
> +/* qemu fw_cfg device is sync today, but spec says it may become async */
> +static void fw_cfg_wait_for_control(struct fw_cfg_dma *d)
> +{
> + do {
> + u32 ctrl = be32_to_cpu(READ_ONCE(d->control));
> +
> + if ((ctrl & ~FW_CFG_DMA_CTL_ERROR) == 0)
> + return;
> +
> + usleep_range(50, 100);
> + } while (true);
And you need an smp rmb here.
> +}
> +
> +static ssize_t fw_cfg_dma_transfer(void *address, u32 length, u32 control)
> +{
> + phys_addr_t dma;
> + struct fw_cfg_dma *d = NULL;
> + ssize_t ret = length;
> +
> + d = kmalloc(sizeof(*d), GFP_KERNEL);
> + if (!d) {
> + ret = -ENOMEM;
> + goto end;
> + }
> +
> + *d = (struct fw_cfg_dma) {
> + .address = address ? cpu_to_be64(virt_to_phys(address)) : 0,
> + .length = cpu_to_be32(length),
> + .control = cpu_to_be32(control)
> + };
> +
> + dma = virt_to_phys(d);
Pls add docs on why this DMA bypasses the DMA API.
> +
> + iowrite32be((u64)dma >> 32, fw_cfg_reg_dma);
> + iowrite32be(dma, fw_cfg_reg_dma + 4);
> +
> + fw_cfg_wait_for_control(d);
> +
> + if (be32_to_cpu(READ_ONCE(d->control)) & FW_CFG_DMA_CTL_ERROR) {
> + ret = -EIO;
> + }
> +
> +end:
> + kfree(d);
> +
> + return ret;
> +}
> +
> /* read chunk of given fw_cfg blob (caller responsible for sanity-check) */
> static inline void fw_cfg_read_blob(u16 key,
> void *buf, loff_t pos, size_t count)
> @@ -103,6 +177,47 @@ static inline void fw_cfg_read_blob(u16 key,
> acpi_release_global_lock(glk);
> }
>
> +#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)
fw_cfg_dma_write seems like a nicer name.
> +{
> + 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__);
> + 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)
> {
> @@ -201,9 +316,6 @@ static int fw_cfg_do_platform_probe(struct
> platform_device *pdev)
> return 0;
> }
>
> -/* fw_cfg revision attribute, in /sys/firmware/qemu_fw_cfg top-level dir. */
> -static u32 fw_cfg_rev;
> -
> static ssize_t fw_cfg_showrev(struct kobject *k, struct attribute *a, char
> *buf)
> {
> return sprintf(buf, "%u\n", fw_cfg_rev);
> @@ -224,6 +336,37 @@ struct fw_cfg_sysfs_entry {
> struct list_head list;
> };
>
> +#ifdef CONFIG_CRASH_CORE
> +static ssize_t write_vmcoreinfo(const struct fw_cfg_file *f)
why not prefix with fw_cfg here?
> +{
> + struct vmci {
> + __le16 host_format;
> + __le16 guest_format;
> + __le32 size;
> + __le64 paddr;
> + } __packed;
No need for the __packed attribute.
And pls do not declare structures within functions.
Name them sanely and place in a header or near top of file.
> + static struct vmci *data;
> + ssize_t ret;
> +
> + data = kmalloc(sizeof(struct vmci), GFP_KERNEL);
> + if (!data)
> + return -ENOMEM;
> +
> + *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())
> + };
> + /* spare ourself reading host format support for now since we
> + * don't know what else to format - host may ignore ours
> + */
> + 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)
> {
> @@ -464,6 +607,14 @@ 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 (fw_cfg_dma_enabled() &&
> + 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)
> --
> 2.16.1.73.g5832b7e9f2
