iommu/vt-d: Avoid memory allocation in iommu_suspend()

The iommu_suspend() syscore suspend callback is invoked with IRQ disabled.
Allocating memory with the GFP_KERNEL flag may re-enable IRQs during
the suspend callback, which can cause intermittent suspend/hibernation
problems with the following kernel traces:

Calling iommu_suspend+0x0/0x1d0
------------[ cut here ]------------
WARNING: CPU: 0 PID: 15 at kernel/time/timekeeping.c:868 ktime_get+0x9b/0xb0
...
CPU: 0 PID: 15 Comm: rcu_preempt Tainted: G     U      E      6.3-intel #r1
RIP: 0010:ktime_get+0x9b/0xb0
...
Call Trace:
 <IRQ>
 tick_sched_timer+0x22/0x90
 ? __pfx_tick_sched_timer+0x10/0x10
 __hrtimer_run_queues+0x111/0x2b0
 hrtimer_interrupt+0xfa/0x230
 __sysvec_apic_timer_interrupt+0x63/0x140
 sysvec_apic_timer_interrupt+0x7b/0xa0
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x1f/0x30
...
------------[ cut here ]------------
Interrupts enabled after iommu_suspend+0x0/0x1d0
WARNING: CPU: 0 PID: 27420 at drivers/base/syscore.c:68 syscore_suspend+0x147/0x270
CPU: 0 PID: 27420 Comm: rtcwake Tainted: G     U  W   E      6.3-intel #r1
RIP: 0010:syscore_suspend+0x147/0x270
...
Call Trace:
 <TASK>
 hibernation_snapshot+0x25b/0x670
 hibernate+0xcd/0x390
 state_store+0xcf/0xe0
 kobj_attr_store+0x13/0x30
 sysfs_kf_write+0x3f/0x50
 kernfs_fop_write_iter+0x128/0x200
 vfs_write+0x1fd/0x3c0
 ksys_write+0x6f/0xf0
 __x64_sys_write+0x1d/0x30
 do_syscall_64+0x3b/0x90
 entry_SYSCALL_64_after_hwframe+0x72/0xdc

Given that only 4 words memory is needed, avoid the memory allocation in
iommu_suspend().

CC: [email protected]
Fixes: 33e0715 ("iommu/vt-d: Avoid GFP_ATOMIC where it is not needed")
Signed-off-by: Zhang Rui <[email protected]>
Tested-by: Ooi, Chin Hao <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Lu Baolu <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Joerg Roedel <[email protected]>

Author: zhang-rui

drivers/iommu/intel/iommu.c

@@ -2998,13 +2998,6 @@ static int iommu_suspend(void)
 	struct intel_iommu *iommu = NULL;
 	unsigned long flag;
 
-	for_each_active_iommu(iommu, drhd) {
-		iommu->iommu_state = kcalloc(MAX_SR_DMAR_REGS, sizeof(u32),
-					     GFP_KERNEL);
-		if (!iommu->iommu_state)
-			goto nomem;
-	}
-
 	iommu_flush_all();
 
 	for_each_active_iommu(iommu, drhd) {
@@ -3024,12 +3017,6 @@ static int iommu_suspend(void)
 		raw_spin_unlock_irqrestore(&iommu->register_lock, flag);
 	}
 	return 0;
-
-nomem:
-	for_each_active_iommu(iommu, drhd)
-		kfree(iommu->iommu_state);
-
-	return -ENOMEM;
 }
 
 static void iommu_resume(void)
@@ -3061,9 +3048,6 @@ static void iommu_resume(void)
 
 		raw_spin_unlock_irqrestore(&iommu->register_lock, flag);
 	}
-
-	for_each_active_iommu(iommu, drhd)
-		kfree(iommu->iommu_state);
 }
 
 static struct syscore_ops iommu_syscore_ops = {

drivers/iommu/intel/iommu.h

@@ -681,7 +681,7 @@ struct intel_iommu {
 	struct iopf_queue *iopf_queue;
 	unsigned char iopfq_name[16];
 	struct q_inval  *qi;            /* Queued invalidation info */
-	u32 *iommu_state; /* Store iommu states between suspend and resume.*/
+	u32 iommu_state[MAX_SR_DMAR_REGS]; /* Store iommu states between suspend and resume.*/
 
 #ifdef CONFIG_IRQ_REMAP
 	struct ir_table *ir_table;	/* Interrupt remapping info */