dmaengine: idxd: Only call idxd_enable_system_pasid() if succeeded in enabling SVA feature

On a Sapphire Rapids system if boot without intel_iommu=on, the IDXD
driver will crash during probe in iommu_sva_bind_device().

[   21.423729] BUG: kernel NULL pointer dereference, address: 0000000000000038
[   21.445108] #PF: supervisor read access in kernel mode
[   21.450912] #PF: error_code(0x0000) - not-present page
[   21.456706] PGD 0
[   21.459047] Oops: 0000 [#1] PREEMPT SMP NOPTI
[   21.464004] CPU: 0 PID: 1420 Comm: kworker/0:3 Not tainted 5.19.0-0.rc3.27.eln120.x86_64 #1
[   21.464011] Hardware name: Intel Corporation EAGLESTREAM/EAGLESTREAM, BIOS EGSDCRB1.SYS.0067.D12.2110190954 10/19/2021
[   21.464015] Workqueue: events work_for_cpu_fn
[   21.464030] RIP: 0010:iommu_sva_bind_device+0x1d/0xe0
[   21.464046] Code: c3 cc 66 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 41 57 41 56 49 89 d6 41 55 41 54 55 53 48 83 ec 08 48 8b 87 d8 02 00 00 <48> 8b 40 38 48 8b 50 10 48 83 7a 70 00 48 89 14 24 0f 84 91 00 00
[   21.464050] RSP: 0018:ff7245d9096b7db8 EFLAGS: 00010296
[   21.464054] RAX: 0000000000000000 RBX: ff1eadeec8a51000 RCX: 0000000000000000
[   21.464058] RDX: ff7245d9096b7e24 RSI: 0000000000000000 RDI: ff1eadeec8a510d0
[   21.464060] RBP: ff1eadeec8a51000 R08: ffffffffb1a12300 R09: ff1eadffbfce25b4
[   21.464062] R10: ffffffffffffffff R11: 0000000000000038 R12: ffffffffc09f8000
[   21.464065] R13: ff1eadeec8a510d0 R14: ff7245d9096b7e24 R15: ff1eaddf54429000
[   21.464067] FS:  0000000000000000(0000) GS:ff1eadee7f600000(0000) knlGS:0000000000000000
[   21.464070] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   21.464072] CR2: 0000000000000038 CR3: 00000008c0e10006 CR4: 0000000000771ef0
[   21.464074] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[   21.464076] DR3: 0000000000000000 DR6: 00000000fffe07f0 DR7: 0000000000000400
[   21.464078] PKRU: 55555554
[   21.464079] Call Trace:
[   21.464083]  <TASK>
[   21.464092]  idxd_pci_probe+0x259/0x1070 [idxd]
[   21.464121]  local_pci_probe+0x3e/0x80
[   21.464132]  work_for_cpu_fn+0x13/0x20
[   21.464136]  process_one_work+0x1c4/0x380
[   21.464143]  worker_thread+0x1ab/0x380
[   21.464147]  ? _raw_spin_lock_irqsave+0x23/0x50
[   21.464158]  ? process_one_work+0x380/0x380
[   21.464161]  kthread+0xe6/0x110
[   21.464168]  ? kthread_complete_and_exit+0x20/0x20
[   21.464172]  ret_from_fork+0x1f/0x30

iommu_sva_bind_device() requires SVA has been enabled successfully on
the IDXD device before it's called. Otherwise, iommu_sva_bind_device()
will access a NULL pointer. If Intel IOMMU is disabled, SVA cannot be
enabled and thus idxd_enable_system_pasid() and iommu_sva_bind_device()
should not be called.

Fixes: 42a1b73 ("dmaengine: idxd: Separate user and kernel pasid enabling")
Cc: Vinod Koul <vkoul@kernel.org>
Cc: linux-kernel@vger.kernel.org
Cc: Dave Jiang <dave.jiang@intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Link: https://lore.kernel.org/dmaengine/20220623170232.6whonfjuh3m5vcoy@cantor/
Signed-off-by: Jerry Snitselaar <jsnitsel@redhat.com>
Acked-by: Fenghua Yu <fenghua.yu@intel.com>
Link: https://lore.kernel.org/r/20220626051648.14249-1-jsnitsel@redhat.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>

Author: snits

drivers/dma/idxd/init.c

@@ -512,15 +512,16 @@ static int idxd_probe(struct idxd_device *idxd)
 	dev_dbg(dev, "IDXD reset complete\n");
 
 	if (IS_ENABLED(CONFIG_INTEL_IDXD_SVM) && sva) {
-		if (iommu_dev_enable_feature(dev, IOMMU_DEV_FEAT_SVA))
+		if (iommu_dev_enable_feature(dev, IOMMU_DEV_FEAT_SVA)) {
 			dev_warn(dev, "Unable to turn on user SVA feature.\n");
-		else
+		} else {
 			set_bit(IDXD_FLAG_USER_PASID_ENABLED, &idxd->flags);
 
-		if (idxd_enable_system_pasid(idxd))
-			dev_warn(dev, "No in-kernel DMA with PASID.\n");
-		else
-			set_bit(IDXD_FLAG_PASID_ENABLED, &idxd->flags);
+			if (idxd_enable_system_pasid(idxd))
+				dev_warn(dev, "No in-kernel DMA with PASID.\n");
+			else
+				set_bit(IDXD_FLAG_PASID_ENABLED, &idxd->flags);
+		}
 	} else if (!sva) {
 		dev_warn(dev, "User forced SVA off via module param.\n");
 	}