No functional changes expected.
Yanfei Xu (2):
iommu/vt-d: Remove the dead code in init_iommu_hw()
iommu/vt-d: Use BUG_ON to check NULL value of 'table'
drivers/iommu/intel/iommu.c | 14 +++-----------
1 file changed, 3 insertions(+), 11 deletions(-)
--
2.34.1
Checking NULL value of 'table' variable deserves a BUG_ON as the
following code will trigger a crash by dereferencing the NULL
'table' pointer. Crash in advance with BUG_ON to avoid WARN_ON
plus NULL pointer dereferencing can simplify the crash log.
Signed-off-by: Yanfei Xu <[email protected]>
---
drivers/iommu/intel/iommu.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
index e98f1b122b49..8aa3bfdb7f95 100644
--- a/drivers/iommu/intel/iommu.c
+++ b/drivers/iommu/intel/iommu.c
@@ -1944,7 +1944,7 @@ static int domain_context_mapping_one(struct dmar_domain *domain,
if (sm_supported(iommu)) {
unsigned long pds;
- WARN_ON(!table);
+ BUG_ON(!table);
/* Setup the PASID DIR pointer: */
pds = context_get_sm_pds(table);
--
2.34.1
After 'commit 2a41ccee2fdc ("iommu/vt-d: Change
iommu_enable/disable_translation to return void")', init_iommu_hw() only
returns 0. If statement for return value of this function is meaningless.
Hence change init_iommu_hw() to return viod and remove the dead code of
if statement in init_iommu_hw()
Signed-off-by: Yanfei Xu <[email protected]>
---
drivers/iommu/intel/iommu.c | 12 ++----------
1 file changed, 2 insertions(+), 10 deletions(-)
diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
index 8096273b034c..e98f1b122b49 100644
--- a/drivers/iommu/intel/iommu.c
+++ b/drivers/iommu/intel/iommu.c
@@ -2963,7 +2963,7 @@ static void __init init_no_remapping_devices(void)
}
#ifdef CONFIG_SUSPEND
-static int init_iommu_hw(void)
+static void init_iommu_hw(void)
{
struct dmar_drhd_unit *drhd;
struct intel_iommu *iommu = NULL;
@@ -2988,8 +2988,6 @@ static int init_iommu_hw(void)
iommu_enable_translation(iommu);
iommu_disable_protect_mem_regions(iommu);
}
-
- return 0;
}
static void iommu_flush_all(void)
@@ -3051,13 +3049,7 @@ static void iommu_resume(void)
struct intel_iommu *iommu = NULL;
unsigned long flag;
- if (init_iommu_hw()) {
- if (force_on)
- panic("tboot: IOMMU setup failed, DMAR can not resume!\n");
- else
- WARN(1, "IOMMU setup failed, DMAR can not resume!\n");
- return;
- }
+ init_iommu_hw();
for_each_active_iommu(iommu, drhd) {
--
2.34.1
On 5/30/23 5:25 PM, Yanfei Xu wrote:
> Checking NULL value of 'table' variable deserves a BUG_ON as the
> following code will trigger a crash by dereferencing the NULL
> 'table' pointer. Crash in advance with BUG_ON to avoid WARN_ON
> plus NULL pointer dereferencing can simplify the crash log.
>
> Signed-off-by: Yanfei Xu<[email protected]>
> ---
> drivers/iommu/intel/iommu.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
> index e98f1b122b49..8aa3bfdb7f95 100644
> --- a/drivers/iommu/intel/iommu.c
> +++ b/drivers/iommu/intel/iommu.c
> @@ -1944,7 +1944,7 @@ static int domain_context_mapping_one(struct dmar_domain *domain,
> if (sm_supported(iommu)) {
> unsigned long pds;
>
> - WARN_ON(!table);
> + BUG_ON(!table);
BUG_ON() is not recommended. Perhaps,
if (!table)
-ENODEV;
?
Best regards,
baolu
On 5/30/23 5:25 PM, Yanfei Xu wrote:
> After 'commit 2a41ccee2fdc ("iommu/vt-d: Change
> iommu_enable/disable_translation to return void")', init_iommu_hw() only
> returns 0. If statement for return value of this function is meaningless.
> Hence change init_iommu_hw() to return viod and remove the dead code of
> if statement in init_iommu_hw()
>
> Signed-off-by: Yanfei Xu<[email protected]>
> ---
> drivers/iommu/intel/iommu.c | 12 ++----------
> 1 file changed, 2 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
> index 8096273b034c..e98f1b122b49 100644
> --- a/drivers/iommu/intel/iommu.c
> +++ b/drivers/iommu/intel/iommu.c
> @@ -2963,7 +2963,7 @@ static void __init init_no_remapping_devices(void)
> }
>
> #ifdef CONFIG_SUSPEND
> -static int init_iommu_hw(void)
> +static void init_iommu_hw(void)
> {
> struct dmar_drhd_unit *drhd;
> struct intel_iommu *iommu = NULL;
> @@ -2988,8 +2988,6 @@ static int init_iommu_hw(void)
> iommu_enable_translation(iommu);
> iommu_disable_protect_mem_regions(iommu);
> }
> -
> - return 0;
2966 static int init_iommu_hw(void)
2967 {
2968 struct dmar_drhd_unit *drhd;
2969 struct intel_iommu *iommu = NULL;
2970
2971 for_each_active_iommu(iommu, drhd)
2972 if (iommu->qi)
2973 dmar_reenable_qi(iommu);
dmar_reenable_qi() still possibly returns an error number. It's better
to pass this error number to the caller of init_iommu_hw()?
2974
2975 for_each_iommu(iommu, drhd) {
2976 if (drhd->ignored) {
Best regards,
baolu
Hi Baolu,
On 5/31/2023 11:24 AM, Baolu Lu wrote:
> On 5/30/23 5:25 PM, Yanfei Xu wrote:
>> After 'commit 2a41ccee2fdc ("iommu/vt-d: Change
>> iommu_enable/disable_translation to return void")', init_iommu_hw() only
>> returns 0. If statement for return value of this function is
>> meaningless.
>> Hence change init_iommu_hw() to return viod and remove the dead code of
>> if statement in init_iommu_hw()
>>
>> Signed-off-by: Yanfei Xu<[email protected]>
>> ---
>> drivers/iommu/intel/iommu.c | 12 ++----------
>> 1 file changed, 2 insertions(+), 10 deletions(-)
>>
>> diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
>> index 8096273b034c..e98f1b122b49 100644
>> --- a/drivers/iommu/intel/iommu.c
>> +++ b/drivers/iommu/intel/iommu.c
>> @@ -2963,7 +2963,7 @@ static void __init init_no_remapping_devices(void)
>> }
>> #ifdef CONFIG_SUSPEND
>> -static int init_iommu_hw(void)
>> +static void init_iommu_hw(void)
>> {
>> struct dmar_drhd_unit *drhd;
>> struct intel_iommu *iommu = NULL;
>> @@ -2988,8 +2988,6 @@ static int init_iommu_hw(void)
>> iommu_enable_translation(iommu);
>> iommu_disable_protect_mem_regions(iommu);
>> }
>> -
>> - return 0;
>
> 2966 static int init_iommu_hw(void)
> 2967 {
> 2968 struct dmar_drhd_unit *drhd;
> 2969 struct intel_iommu *iommu = NULL;
> 2970
> 2971 for_each_active_iommu(iommu, drhd)
> 2972 if (iommu->qi)
> 2973 dmar_reenable_qi(iommu);
>
> dmar_reenable_qi() still possibly returns an error number. It's better
> to pass this error number to the caller of init_iommu_hw()?
>
Event dmar_reenable_qi can return error number, but there is no caller
check it. As below, only these two places invoke it:
1. init_iommu_hw->dmar_reenable_qi
2. reenable_irq_remapping->dmar_reenable_qi
I think we can also convert dmar_reenable_qi() to return void:
diff --git a/drivers/iommu/intel/dmar.c b/drivers/iommu/intel/dmar.c
index a3414afe11b0..1432483c79e8 100644
--- a/drivers/iommu/intel/dmar.c
+++ b/drivers/iommu/intel/dmar.c
@@ -2112,13 +2112,10 @@ int __init enable_drhd_fault_handling(void)
/*
* Re-enable Queued Invalidation interface.
*/
-int dmar_reenable_qi(struct intel_iommu *iommu)
+void dmar_reenable_qi(struct intel_iommu *iommu)
{
- if (!ecap_qis(iommu->ecap))
- return -ENOENT;
-
- if (!iommu->qi)
- return -ENOENT;
+ WARN_ON(!iommu->qi || !ecap_qis(iommu->ecap))
+ return;
/*
* First disable queued invalidation.
@@ -2130,8 +2127,6 @@ int dmar_reenable_qi(struct intel_iommu *iommu)
* invalidation.
*/
__dmar_enable_qi(iommu);
-
- return 0;
}
From my understanding, dmar_reenable_qi() is used in suspend/resume case,
so the extended cap of an existing IOMMU hardware is unlikely changed. As
for the check of iommu->qi, if dmar_reenable_qi() can be invoked all is
depended on the no-NULL of iommu->qi at first. How about using WARN_ON for
both of them to simply this function.
Thanks,
Yanfei
> 2974
> 2975 for_each_iommu(iommu, drhd) {
> 2976 if (drhd->ignored) {
>
> Best regards,
> baolu
Hi Baolu,
On 5/31/2023 11:26 AM, Baolu Lu wrote:
> On 5/30/23 5:25 PM, Yanfei Xu wrote:
>> Checking NULL value of 'table' variable deserves a BUG_ON as the
>> following code will trigger a crash by dereferencing the NULL
>> 'table' pointer. Crash in advance with BUG_ON to avoid WARN_ON
>> plus NULL pointer dereferencing can simplify the crash log.
>>
>> Signed-off-by: Yanfei Xu<[email protected]>
>> ---
>> drivers/iommu/intel/iommu.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
>> index e98f1b122b49..8aa3bfdb7f95 100644
>> --- a/drivers/iommu/intel/iommu.c
>> +++ b/drivers/iommu/intel/iommu.c
>> @@ -1944,7 +1944,7 @@ static int domain_context_mapping_one(struct
>> dmar_domain *domain,
>> if (sm_supported(iommu)) {
>> unsigned long pds;
>> - WARN_ON(!table);
>> + BUG_ON(!table);
>
> BUG_ON() is not recommended. Perhaps,
>
> if (!table)
> -ENODEV;
>
Agree:) It is always better to handle the error than crash kernel.
How about:
diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
index 8096273b034c..7f077e3a4128 100644
--- a/drivers/iommu/intel/iommu.c
+++ b/drivers/iommu/intel/iommu.c
@@ -1944,7 +1944,10 @@ static int domain_context_mapping_one(struct
dmar_domain *domain,
if (sm_supported(iommu)) {
unsigned long pds;
- WARN_ON(!table);
+ if (WARN_ON(!table)) {
+ ret = -ENODEV;
+ goto out_unlock;
+ }
Thanks,
Yanfei
> ?
>
> Best regards,
> baolu
On 5/31/23 2:55 PM, Yanfei Xu wrote:
>
> On 5/31/2023 11:24 AM, Baolu Lu wrote:
>> On 5/30/23 5:25 PM, Yanfei Xu wrote:
>>> After 'commit 2a41ccee2fdc ("iommu/vt-d: Change
>>> iommu_enable/disable_translation to return void")', init_iommu_hw() only
>>> returns 0. If statement for return value of this function is
>>> meaningless.
>>> Hence change init_iommu_hw() to return viod and remove the dead code of
>>> if statement in init_iommu_hw()
>>>
>>> Signed-off-by: Yanfei Xu<[email protected]>
>>> ---
>>> drivers/iommu/intel/iommu.c | 12 ++----------
>>> 1 file changed, 2 insertions(+), 10 deletions(-)
>>>
>>> diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
>>> index 8096273b034c..e98f1b122b49 100644
>>> --- a/drivers/iommu/intel/iommu.c
>>> +++ b/drivers/iommu/intel/iommu.c
>>> @@ -2963,7 +2963,7 @@ static void __init init_no_remapping_devices(void)
>>> }
>>> #ifdef CONFIG_SUSPEND
>>> -static int init_iommu_hw(void)
>>> +static void init_iommu_hw(void)
>>> {
>>> struct dmar_drhd_unit *drhd;
>>> struct intel_iommu *iommu = NULL;
>>> @@ -2988,8 +2988,6 @@ static int init_iommu_hw(void)
>>> iommu_enable_translation(iommu);
>>> iommu_disable_protect_mem_regions(iommu);
>>> }
>>> -
>>> - return 0;
>>
>> 2966 static int init_iommu_hw(void)
>> 2967 {
>> 2968 struct dmar_drhd_unit *drhd;
>> 2969 struct intel_iommu *iommu = NULL;
>> 2970
>> 2971 for_each_active_iommu(iommu, drhd)
>> 2972 if (iommu->qi)
>> 2973 dmar_reenable_qi(iommu);
>>
>> dmar_reenable_qi() still possibly returns an error number. It's better
>> to pass this error number to the caller of init_iommu_hw()?
>>
> Event dmar_reenable_qi can return error number, but there is no caller
> check it. As below, only these two places invoke it:
> 1. init_iommu_hw->dmar_reenable_qi
> 2. reenable_irq_remapping->dmar_reenable_qi
>
> I think we can also convert dmar_reenable_qi() to return void:
> diff --git a/drivers/iommu/intel/dmar.c b/drivers/iommu/intel/dmar.c
> index a3414afe11b0..1432483c79e8 100644
> --- a/drivers/iommu/intel/dmar.c
> +++ b/drivers/iommu/intel/dmar.c
> @@ -2112,13 +2112,10 @@ int __init enable_drhd_fault_handling(void)
> /*
> * Re-enable Queued Invalidation interface.
> */
> -int dmar_reenable_qi(struct intel_iommu *iommu)
> +void dmar_reenable_qi(struct intel_iommu *iommu)
> {
> - if (!ecap_qis(iommu->ecap))
> - return -ENOENT;
> -
> - if (!iommu->qi)
> - return -ENOENT;
> + WARN_ON(!iommu->qi || !ecap_qis(iommu->ecap))
> + return;
>
> /*
> * First disable queued invalidation.
> @@ -2130,8 +2127,6 @@ int dmar_reenable_qi(struct intel_iommu *iommu)
> * invalidation.
> */
> __dmar_enable_qi(iommu);
> -
> - return 0;
> }
>
> From my understanding, dmar_reenable_qi() is used in suspend/resume case,
> so the extended cap of an existing IOMMU hardware is unlikely changed. As
> for the check of iommu->qi, if dmar_reenable_qi() can be invoked all is
> depended on the no-NULL of iommu->qi at first. How about using WARN_ON for
> both of them to simply this function.
This seems to be heading in the opposite direction. Actually any
operation may succeed or fail.
diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
index b871a6afd803..ecc2007a96f9 100644
--- a/drivers/iommu/intel/iommu.c
+++ b/drivers/iommu/intel/iommu.c
@@ -2967,10 +2967,13 @@ static int init_iommu_hw(void)
{
struct dmar_drhd_unit *drhd;
struct intel_iommu *iommu = NULL;
+ int ret;
- for_each_active_iommu(iommu, drhd)
- if (iommu->qi)
- dmar_reenable_qi(iommu);
+ for_each_active_iommu(iommu, drhd) {
+ ret = dmar_reenable_qi(iommu);
+ if (ret)
+ return ret;
+ }
for_each_iommu(iommu, drhd) {
if (drhd->ignored) {
Best regards,
baolu
On 5/31/23 3:09 PM, Yanfei Xu wrote:
> On 5/31/2023 11:26 AM, Baolu Lu wrote:
>> On 5/30/23 5:25 PM, Yanfei Xu wrote:
>>> Checking NULL value of 'table' variable deserves a BUG_ON as the
>>> following code will trigger a crash by dereferencing the NULL
>>> 'table' pointer. Crash in advance with BUG_ON to avoid WARN_ON
>>> plus NULL pointer dereferencing can simplify the crash log.
>>>
>>> Signed-off-by: Yanfei Xu<[email protected]>
>>> ---
>>> drivers/iommu/intel/iommu.c | 2 +-
>>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
>>> index e98f1b122b49..8aa3bfdb7f95 100644
>>> --- a/drivers/iommu/intel/iommu.c
>>> +++ b/drivers/iommu/intel/iommu.c
>>> @@ -1944,7 +1944,7 @@ static int domain_context_mapping_one(struct
>>> dmar_domain *domain,
>>> if (sm_supported(iommu)) {
>>> unsigned long pds;
>>> - WARN_ON(!table);
>>> + BUG_ON(!table);
>>
>> BUG_ON() is not recommended. Perhaps,
>>
>> if (!table)
>> -ENODEV;
>>
> Agree:) It is always better to handle the error than crash kernel.
>
> How about:
> diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
> index 8096273b034c..7f077e3a4128 100644
> --- a/drivers/iommu/intel/iommu.c
> +++ b/drivers/iommu/intel/iommu.c
> @@ -1944,7 +1944,10 @@ static int domain_context_mapping_one(struct
> dmar_domain *domain,
> if (sm_supported(iommu)) {
> unsigned long pds;
>
> - WARN_ON(!table);
> + if (WARN_ON(!table)) {
> + ret = -ENODEV;
> + goto out_unlock;
> + }
I'd recommend to remove this line directly. This pointer will be
accessed in the following code, if empty "table" really happens, the
kernel will report a NULL pointer reference warning at the first place.
In the same function, I also saw "WARN_ON(did == 0);". It's unnecessary
as domain_id_iommu() will never return 0. Perhaps we can clean it up as
well.
Best regards,
baolu
On 6/1/2023 9:23 AM, Baolu Lu wrote:
> On 5/31/23 3:09 PM, Yanfei Xu wrote:
>> On 5/31/2023 11:26 AM, Baolu Lu wrote:
>>> On 5/30/23 5:25 PM, Yanfei Xu wrote:
>>>> Checking NULL value of 'table' variable deserves a BUG_ON as the
>>>> following code will trigger a crash by dereferencing the NULL
>>>> 'table' pointer. Crash in advance with BUG_ON to avoid WARN_ON
>>>> plus NULL pointer dereferencing can simplify the crash log.
>>>>
>>>> Signed-off-by: Yanfei Xu<[email protected]>
>>>> ---
>>>> drivers/iommu/intel/iommu.c | 2 +-
>>>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>>>
>>>> diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
>>>> index e98f1b122b49..8aa3bfdb7f95 100644
>>>> --- a/drivers/iommu/intel/iommu.c
>>>> +++ b/drivers/iommu/intel/iommu.c
>>>> @@ -1944,7 +1944,7 @@ static int domain_context_mapping_one(struct
>>>> dmar_domain *domain,
>>>> if (sm_supported(iommu)) {
>>>> unsigned long pds;
>>>> - WARN_ON(!table);
>>>> + BUG_ON(!table);
>>>
>>> BUG_ON() is not recommended. Perhaps,
>>>
>>> if (!table)
>>> -ENODEV;
>>>
>> Agree:) It is always better to handle the error than crash kernel.
>>
>> How about:
>> diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
>> index 8096273b034c..7f077e3a4128 100644
>> --- a/drivers/iommu/intel/iommu.c
>> +++ b/drivers/iommu/intel/iommu.c
>> @@ -1944,7 +1944,10 @@ static int domain_context_mapping_one(struct
>> dmar_domain *domain,
>> if (sm_supported(iommu)) {
>> unsigned long pds;
>>
>> - WARN_ON(!table);
>> + if (WARN_ON(!table)) {
>> + ret = -ENODEV;
>> + goto out_unlock;
>> + }
>
> I'd recommend to remove this line directly. This pointer will be
> accessed in the following code, if empty "table" really happens, the
> kernel will report a NULL pointer reference warning at the first place.
>
> In the same function, I also saw "WARN_ON(did == 0);". It's unnecessary
> as domain_id_iommu() will never return 0. Perhaps we can clean it up as
> well.
Will do in V2.
Thanks,
Yanfei
>
> Best regards,
> baolu
On 6/1/2023 9:15 AM, Baolu Lu wrote:
> On 5/31/23 2:55 PM, Yanfei Xu wrote:
>>
>> On 5/31/2023 11:24 AM, Baolu Lu wrote:
>>> On 5/30/23 5:25 PM, Yanfei Xu wrote:
>>>> After 'commit 2a41ccee2fdc ("iommu/vt-d: Change
>>>> iommu_enable/disable_translation to return void")', init_iommu_hw()
>>>> only
>>>> returns 0. If statement for return value of this function is
>>>> meaningless.
>>>> Hence change init_iommu_hw() to return viod and remove the dead
>>>> code of
>>>> if statement in init_iommu_hw()
>>>>
>>>> Signed-off-by: Yanfei Xu<[email protected]>
>>>> ---
>>>> drivers/iommu/intel/iommu.c | 12 ++----------
>>>> 1 file changed, 2 insertions(+), 10 deletions(-)
>>>>
>>>> diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
>>>> index 8096273b034c..e98f1b122b49 100644
>>>> --- a/drivers/iommu/intel/iommu.c
>>>> +++ b/drivers/iommu/intel/iommu.c
>>>> @@ -2963,7 +2963,7 @@ static void __init
>>>> init_no_remapping_devices(void)
>>>> }
>>>> #ifdef CONFIG_SUSPEND
>>>> -static int init_iommu_hw(void)
>>>> +static void init_iommu_hw(void)
>>>> {
>>>> struct dmar_drhd_unit *drhd;
>>>> struct intel_iommu *iommu = NULL;
>>>> @@ -2988,8 +2988,6 @@ static int init_iommu_hw(void)
>>>> iommu_enable_translation(iommu);
>>>> iommu_disable_protect_mem_regions(iommu);
>>>> }
>>>> -
>>>> - return 0;
>>>
>>> 2966 static int init_iommu_hw(void)
>>> 2967 {
>>> 2968 struct dmar_drhd_unit *drhd;
>>> 2969 struct intel_iommu *iommu = NULL;
>>> 2970
>>> 2971 for_each_active_iommu(iommu, drhd)
>>> 2972 if (iommu->qi)
>>> 2973 dmar_reenable_qi(iommu);
>>>
>>> dmar_reenable_qi() still possibly returns an error number. It's better
>>> to pass this error number to the caller of init_iommu_hw()?
>>>
>> Event dmar_reenable_qi can return error number, but there is no caller
>> check it. As below, only these two places invoke it:
>> 1. init_iommu_hw->dmar_reenable_qi
>> 2. reenable_irq_remapping->dmar_reenable_qi
>>
>> I think we can also convert dmar_reenable_qi() to return void:
>> diff --git a/drivers/iommu/intel/dmar.c b/drivers/iommu/intel/dmar.c
>> index a3414afe11b0..1432483c79e8 100644
>> --- a/drivers/iommu/intel/dmar.c
>> +++ b/drivers/iommu/intel/dmar.c
>> @@ -2112,13 +2112,10 @@ int __init enable_drhd_fault_handling(void)
>> /*
>> * Re-enable Queued Invalidation interface.
>> */
>> -int dmar_reenable_qi(struct intel_iommu *iommu)
>> +void dmar_reenable_qi(struct intel_iommu *iommu)
>> {
>> - if (!ecap_qis(iommu->ecap))
>> - return -ENOENT;
>> -
>> - if (!iommu->qi)
>> - return -ENOENT;
>> + WARN_ON(!iommu->qi || !ecap_qis(iommu->ecap))
>> + return;
>>
>> /*
>> * First disable queued invalidation.
>> @@ -2130,8 +2127,6 @@ int dmar_reenable_qi(struct intel_iommu *iommu)
>> * invalidation.
>> */
>> __dmar_enable_qi(iommu);
>> -
>> - return 0;
>> }
>>
>> From my understanding, dmar_reenable_qi() is used in suspend/resume
>> case,
>> so the extended cap of an existing IOMMU hardware is unlikely
>> changed. As
>> for the check of iommu->qi, if dmar_reenable_qi() can be invoked all is
>> depended on the no-NULL of iommu->qi at first. How about using
>> WARN_ON for
>> both of them to simply this function.
>
> This seems to be heading in the opposite direction. Actually any
> operation may succeed or fail.
>
> diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
> index b871a6afd803..ecc2007a96f9 100644
> --- a/drivers/iommu/intel/iommu.c
> +++ b/drivers/iommu/intel/iommu.c
> @@ -2967,10 +2967,13 @@ static int init_iommu_hw(void)
> {
> struct dmar_drhd_unit *drhd;
> struct intel_iommu *iommu = NULL;
> + int ret;
>
> - for_each_active_iommu(iommu, drhd)
> - if (iommu->qi)
> - dmar_reenable_qi(iommu);
> + for_each_active_iommu(iommu, drhd) {
> + ret = dmar_reenable_qi(iommu);
> + if (ret)
> + return ret;
For confirm, you mean this?
@@ -2967,10 +2970,14 @@ static int init_iommu_hw(void)
{
struct dmar_drhd_unit *drhd;
struct intel_iommu *iommu = NULL;
+ int ret;
- for_each_active_iommu(iommu, drhd)
+ for_each_active_iommu(iommu, drhd) {
if (iommu->qi)
- dmar_reenable_qi(iommu);
+ ret = dmar_reenable_qi(iommu);
+ if (ret)
+ return ret;
+ }
If drop NULL value check of iommu->qi, dmar_reenable_qi() may
return minus value to break the loop of dmar_reenable_qi as
one of iommus doesn't set up iommu->qi.
Thanks,
Yanfei
> + }
>
> for_each_iommu(iommu, drhd) {
> if (drhd->ignored) {
>
> Best regards,
> baolu
On Wed, May 31, 2023 at 11:26:55AM +0800, Baolu Lu wrote:
> On 5/30/23 5:25 PM, Yanfei Xu wrote:
> > Checking NULL value of 'table' variable deserves a BUG_ON as the
> > following code will trigger a crash by dereferencing the NULL
> > 'table' pointer. Crash in advance with BUG_ON to avoid WARN_ON
> > plus NULL pointer dereferencing can simplify the crash log.
> >
> > Signed-off-by: Yanfei Xu<[email protected]>
> > ---
> > drivers/iommu/intel/iommu.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
> > index e98f1b122b49..8aa3bfdb7f95 100644
> > --- a/drivers/iommu/intel/iommu.c
> > +++ b/drivers/iommu/intel/iommu.c
> > @@ -1944,7 +1944,7 @@ static int domain_context_mapping_one(struct dmar_domain *domain,
> > if (sm_supported(iommu)) {
> > unsigned long pds;
> > - WARN_ON(!table);
> > + BUG_ON(!table);
>
> BUG_ON() is not recommended. Perhaps,
>
> if (!table)
> -ENODEV;
>
> ?
If it is not something you think needs active debugging then just let
it crash on the NULL pointer deref. You get a nice backtrace from that
already.
The additional value of the WARN is it gives you a line number, a
prettier print and it might recover more cleanly (or not, it might
just crash somewhere else).
Jason