Re: [Qemu-devel] [PATCH v4 5/5] fw_cfg: write vmcoreinfo details

[Gabriel L. Somlo]

On Tue, Oct 31, 2017 at 04:19:38PM +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 

Same two questions as for 3/5 earlier :)

Thanks,
--G

> ---
>  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 8ce5e49b7c62..ebd9bb134900 100644
> --- a/drivers/firmware/qemu_fw_cfg.c
> +++ b/drivers/firmware/qemu_fw_cfg.c
> @@ -35,6 +35,8 @@
>  #include 
>  #include 
>  #include 
> +#include 
> +#include 
>  
>  MODULE_AUTHOR("Gabriel L. Somlo ");
>  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, );
> + 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;

Same question as before: why not e.g. EINVAL?

> + }
> +
> + mutex_lock(_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);

NULL?

> + if (ret < 0)
> + goto end;
> + ret = fw_cfg_dma_transfer(buf, count, FW_CFG_DMA_CTL_WRITE);
> + }
> +
> +end:
> + mutex_unlock(_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");
> + }
> 

[Qemu-devel] [PATCH v4 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 
---
 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 8ce5e49b7c62..ebd9bb134900 100644
--- a/drivers/firmware/qemu_fw_cfg.c
+++ b/drivers/firmware/qemu_fw_cfg.c
@@ -35,6 +35,8 @@
 #include 
 #include 
 #include 
+#include 
+#include 
 
 MODULE_AUTHOR("Gabriel L. Somlo ");
 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, );
+   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(_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(_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.rc0.40.gaefcc5f6f