Re: [PATCH 1/2] iommu/vt-d: Remove the dead code in init_iommu_hw()
From: Baolu Lu
Date: Wed May 31 2023 - 21:23:20 EST
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<yanfei.xu@xxxxxxxxx>
---
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