Re: [PATCH v16 06/11] fw_cfg: handle fw_cfg_read_blob() error

[Marc-André Lureau]

Hi

On Wed, Feb 28, 2018 at 6:32 PM, Michael S. Tsirkin  wrote:
>> @@ -557,7 +566,10 @@ static int fw_cfg_sysfs_probe(struct platform_device 
>> *pdev)
>>   goto err_probe;
>>
>>   /* get revision number, add matching top-level attribute */
>> - fw_cfg_read_blob(FW_CFG_ID, , 0, sizeof(rev));
>> + err = fw_cfg_read_blob(FW_CFG_ID, , 0, sizeof(rev));
>> + if (err < 0)
>> + goto err_probe;
>> +
>>   fw_cfg_rev = le32_to_cpu(rev);
>>   err = sysfs_create_file(fw_cfg_top_ko, _cfg_rev_attr.attr);
>>   if (err)
>
> So on this one, maybe we should just drop this attribute.
> Does anyone use it?
> Removing it will speed up boot slightly.

We can't skip reading FW_CFG_ID (rev) as we need it to check DMA
support. I don't mind if we remove the sysfs entry, but I doubt it
makes a difference in boot time.

>> --
>> 2.16.1.73.g5832b7e9f2

Re: [PATCH v16 06/11] fw_cfg: handle fw_cfg_read_blob() error

[Marc-André Lureau]

Hi

On Wed, Feb 28, 2018 at 6:32 PM, Michael S. Tsirkin  wrote:
>> @@ -557,7 +566,10 @@ static int fw_cfg_sysfs_probe(struct platform_device 
>> *pdev)
>>   goto err_probe;
>>
>>   /* get revision number, add matching top-level attribute */
>> - fw_cfg_read_blob(FW_CFG_ID, , 0, sizeof(rev));
>> + err = fw_cfg_read_blob(FW_CFG_ID, , 0, sizeof(rev));
>> + if (err < 0)
>> + goto err_probe;
>> +
>>   fw_cfg_rev = le32_to_cpu(rev);
>>   err = sysfs_create_file(fw_cfg_top_ko, _cfg_rev_attr.attr);
>>   if (err)
>
> So on this one, maybe we should just drop this attribute.
> Does anyone use it?
> Removing it will speed up boot slightly.

We can't skip reading FW_CFG_ID (rev) as we need it to check DMA
support. I don't mind if we remove the sysfs entry, but I doubt it
makes a difference in boot time.

>> --
>> 2.16.1.73.g5832b7e9f2

Re: [PATCH v16 06/11] fw_cfg: handle fw_cfg_read_blob() error

[Michael S. Tsirkin]

> @@ -557,7 +566,10 @@ static int fw_cfg_sysfs_probe(struct platform_device 
> *pdev)
>   goto err_probe;
>  
>   /* get revision number, add matching top-level attribute */
> - fw_cfg_read_blob(FW_CFG_ID, , 0, sizeof(rev));
> + err = fw_cfg_read_blob(FW_CFG_ID, , 0, sizeof(rev));
> + if (err < 0)
> + goto err_probe;
> +
>   fw_cfg_rev = le32_to_cpu(rev);
>   err = sysfs_create_file(fw_cfg_top_ko, _cfg_rev_attr.attr);
>   if (err)

So on this one, maybe we should just drop this attribute.
Does anyone use it?
Removing it will speed up boot slightly.

> -- 
> 2.16.1.73.g5832b7e9f2

Re: [PATCH v16 06/11] fw_cfg: handle fw_cfg_read_blob() error

[Michael S. Tsirkin]

> @@ -557,7 +566,10 @@ static int fw_cfg_sysfs_probe(struct platform_device 
> *pdev)
>   goto err_probe;
>  
>   /* get revision number, add matching top-level attribute */
> - fw_cfg_read_blob(FW_CFG_ID, , 0, sizeof(rev));
> + err = fw_cfg_read_blob(FW_CFG_ID, , 0, sizeof(rev));
> + if (err < 0)
> + goto err_probe;
> +
>   fw_cfg_rev = le32_to_cpu(rev);
>   err = sysfs_create_file(fw_cfg_top_ko, _cfg_rev_attr.attr);
>   if (err)

So on this one, maybe we should just drop this attribute.
Does anyone use it?
Removing it will speed up boot slightly.

> -- 
> 2.16.1.73.g5832b7e9f2

[PATCH v16 06/11] fw_cfg: handle fw_cfg_read_blob() error

[Marc-André Lureau]

fw_cfg_read_blob() may fail, but does not return error. This may lead
to surprising behaviours, like populating zero file entries (in
register_file() or during read). Return an error if ACPI locking
failed. Also, the following DMA read/write extension will add more
error paths that should be handled appropriately.

Signed-off-by: Marc-André Lureau 
---
 drivers/firmware/qemu_fw_cfg.c | 32 ++--
 1 file changed, 22 insertions(+), 10 deletions(-)

diff --git a/drivers/firmware/qemu_fw_cfg.c b/drivers/firmware/qemu_fw_cfg.c
index 0cc71d028ae3..45bfc389b226 100644
--- a/drivers/firmware/qemu_fw_cfg.c
+++ b/drivers/firmware/qemu_fw_cfg.c
@@ -77,8 +77,8 @@ static void fw_cfg_sel_endianness(u16 key)
 }
 
 /* read chunk of given fw_cfg blob (caller responsible for sanity-check) */
-static void fw_cfg_read_blob(u16 key,
-   void *buf, loff_t pos, size_t count)
+static ssize_t fw_cfg_read_blob(u16 key,
+   void *buf, loff_t pos, size_t count)
 {
u32 glk = -1U;
acpi_status status;
@@ -91,7 +91,7 @@ static void fw_cfg_read_blob(u16 key,
/* Should never get here */
WARN(1, "fw_cfg_read_blob: Failed to lock ACPI!\n");
memset(buf, 0, count);
-   return;
+   return -EINVAL;
}
 
mutex_lock(_cfg_dev_lock);
@@ -102,6 +102,7 @@ static void fw_cfg_read_blob(u16 key,
mutex_unlock(_cfg_dev_lock);
 
acpi_release_global_lock(glk);
+   return count;
 }
 
 /* clean up fw_cfg device i/o */
@@ -183,8 +184,9 @@ static int fw_cfg_do_platform_probe(struct platform_device 
*pdev)
}
 
/* verify fw_cfg device signature */
-   fw_cfg_read_blob(FW_CFG_SIGNATURE, sig, 0, FW_CFG_SIG_SIZE);
-   if (memcmp(sig, "QEMU", FW_CFG_SIG_SIZE) != 0) {
+   if (fw_cfg_read_blob(FW_CFG_SIGNATURE, sig,
+   0, FW_CFG_SIG_SIZE) < 0 ||
+   memcmp(sig, "QEMU", FW_CFG_SIG_SIZE) != 0) {
fw_cfg_io_cleanup();
return -ENODEV;
}
@@ -344,8 +346,7 @@ static ssize_t fw_cfg_sysfs_read_raw(struct file *filp, 
struct kobject *kobj,
if (count > entry->size - pos)
count = entry->size - pos;
 
-   fw_cfg_read_blob(entry->select, buf, pos, count);
-   return count;
+   return fw_cfg_read_blob(entry->select, buf, pos, count);
 }
 
 static struct bin_attribute fw_cfg_sysfs_attr_raw = {
@@ -501,7 +502,11 @@ static int fw_cfg_register_dir_entries(void)
struct fw_cfg_file *dir;
size_t dir_size;
 
-   fw_cfg_read_blob(FW_CFG_FILE_DIR, _count, 0, sizeof(files_count));
+   ret = fw_cfg_read_blob(FW_CFG_FILE_DIR, _count,
+   0, sizeof(files_count));
+   if (ret < 0)
+   return ret;
+
count = be32_to_cpu(files_count);
dir_size = count * sizeof(struct fw_cfg_file);
 
@@ -509,7 +514,10 @@ static int fw_cfg_register_dir_entries(void)
if (!dir)
return -ENOMEM;
 
-   fw_cfg_read_blob(FW_CFG_FILE_DIR, dir, sizeof(files_count), dir_size);
+   ret = fw_cfg_read_blob(FW_CFG_FILE_DIR, dir,
+   sizeof(files_count), dir_size);
+   if (ret < 0)
+   goto end;
 
for (i = 0; i < count; i++) {
ret = fw_cfg_register_file([i]);
@@ -517,6 +525,7 @@ static int fw_cfg_register_dir_entries(void)
break;
}
 
+end:
kfree(dir);
return ret;
 }
@@ -557,7 +566,10 @@ static int fw_cfg_sysfs_probe(struct platform_device *pdev)
goto err_probe;
 
/* get revision number, add matching top-level attribute */
-   fw_cfg_read_blob(FW_CFG_ID, , 0, sizeof(rev));
+   err = fw_cfg_read_blob(FW_CFG_ID, , 0, sizeof(rev));
+   if (err < 0)
+   goto err_probe;
+
fw_cfg_rev = le32_to_cpu(rev);
err = sysfs_create_file(fw_cfg_top_ko, _cfg_rev_attr.attr);
if (err)
-- 
2.16.1.73.g5832b7e9f2

[PATCH v16 06/11] fw_cfg: handle fw_cfg_read_blob() error

[Marc-André Lureau]

fw_cfg_read_blob() may fail, but does not return error. This may lead
to surprising behaviours, like populating zero file entries (in
register_file() or during read). Return an error if ACPI locking
failed. Also, the following DMA read/write extension will add more
error paths that should be handled appropriately.

Signed-off-by: Marc-André Lureau 
---
 drivers/firmware/qemu_fw_cfg.c | 32 ++--
 1 file changed, 22 insertions(+), 10 deletions(-)

diff --git a/drivers/firmware/qemu_fw_cfg.c b/drivers/firmware/qemu_fw_cfg.c
index 0cc71d028ae3..45bfc389b226 100644
--- a/drivers/firmware/qemu_fw_cfg.c
+++ b/drivers/firmware/qemu_fw_cfg.c
@@ -77,8 +77,8 @@ static void fw_cfg_sel_endianness(u16 key)
 }
 
 /* read chunk of given fw_cfg blob (caller responsible for sanity-check) */
-static void fw_cfg_read_blob(u16 key,
-   void *buf, loff_t pos, size_t count)
+static ssize_t fw_cfg_read_blob(u16 key,
+   void *buf, loff_t pos, size_t count)
 {
u32 glk = -1U;
acpi_status status;
@@ -91,7 +91,7 @@ static void fw_cfg_read_blob(u16 key,
/* Should never get here */
WARN(1, "fw_cfg_read_blob: Failed to lock ACPI!\n");
memset(buf, 0, count);
-   return;
+   return -EINVAL;
}
 
mutex_lock(_cfg_dev_lock);
@@ -102,6 +102,7 @@ static void fw_cfg_read_blob(u16 key,
mutex_unlock(_cfg_dev_lock);
 
acpi_release_global_lock(glk);
+   return count;
 }
 
 /* clean up fw_cfg device i/o */
@@ -183,8 +184,9 @@ static int fw_cfg_do_platform_probe(struct platform_device 
*pdev)
}
 
/* verify fw_cfg device signature */
-   fw_cfg_read_blob(FW_CFG_SIGNATURE, sig, 0, FW_CFG_SIG_SIZE);
-   if (memcmp(sig, "QEMU", FW_CFG_SIG_SIZE) != 0) {
+   if (fw_cfg_read_blob(FW_CFG_SIGNATURE, sig,
+   0, FW_CFG_SIG_SIZE) < 0 ||
+   memcmp(sig, "QEMU", FW_CFG_SIG_SIZE) != 0) {
fw_cfg_io_cleanup();
return -ENODEV;
}
@@ -344,8 +346,7 @@ static ssize_t fw_cfg_sysfs_read_raw(struct file *filp, 
struct kobject *kobj,
if (count > entry->size - pos)
count = entry->size - pos;
 
-   fw_cfg_read_blob(entry->select, buf, pos, count);
-   return count;
+   return fw_cfg_read_blob(entry->select, buf, pos, count);
 }
 
 static struct bin_attribute fw_cfg_sysfs_attr_raw = {
@@ -501,7 +502,11 @@ static int fw_cfg_register_dir_entries(void)
struct fw_cfg_file *dir;
size_t dir_size;
 
-   fw_cfg_read_blob(FW_CFG_FILE_DIR, _count, 0, sizeof(files_count));
+   ret = fw_cfg_read_blob(FW_CFG_FILE_DIR, _count,
+   0, sizeof(files_count));
+   if (ret < 0)
+   return ret;
+
count = be32_to_cpu(files_count);
dir_size = count * sizeof(struct fw_cfg_file);
 
@@ -509,7 +514,10 @@ static int fw_cfg_register_dir_entries(void)
if (!dir)
return -ENOMEM;
 
-   fw_cfg_read_blob(FW_CFG_FILE_DIR, dir, sizeof(files_count), dir_size);
+   ret = fw_cfg_read_blob(FW_CFG_FILE_DIR, dir,
+   sizeof(files_count), dir_size);
+   if (ret < 0)
+   goto end;
 
for (i = 0; i < count; i++) {
ret = fw_cfg_register_file([i]);
@@ -517,6 +525,7 @@ static int fw_cfg_register_dir_entries(void)
break;
}
 
+end:
kfree(dir);
return ret;
 }
@@ -557,7 +566,10 @@ static int fw_cfg_sysfs_probe(struct platform_device *pdev)
goto err_probe;
 
/* get revision number, add matching top-level attribute */
-   fw_cfg_read_blob(FW_CFG_ID, , 0, sizeof(rev));
+   err = fw_cfg_read_blob(FW_CFG_ID, , 0, sizeof(rev));
+   if (err < 0)
+   goto err_probe;
+
fw_cfg_rev = le32_to_cpu(rev);
err = sysfs_create_file(fw_cfg_top_ko, _cfg_rev_attr.attr);
if (err)
-- 
2.16.1.73.g5832b7e9f2