[PATCH rc] iommu/arm-smmu-v3: Do not use GFP_KERNEL under as spinlock

[Will Deacon]

On Tue, Feb 13, 2024 at 10:00:33AM -0400, Jason Gunthorpe wrote:
> On Tue, Feb 13, 2024 at 01:56:28PM +0000, Will Deacon wrote:
> 
> > I can write it as a full patch if you prefer (and I'll need your help to
> > test it), but I was really hoping to continue the discussion so you could
> > spin a v2.
> 
> No worries, I'll take care of it, just need to understand what we have
> agreed.

Cheers. I finished the diff off anyway, as it's basically just merging
the thing I sent with the rest of your patch. What do you reckon?

Will

--->8

diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-sva.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-sva.c
index 05722121f00e..128f61a705c7 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-sva.c
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-sva.c
@@ -588,6 +588,12 @@ static int arm_smmu_sva_set_dev_pasid(struct iommu_domain *domain,
 {
 	int ret = 0;
 	struct mm_struct *mm = domain->mm;
+	struct arm_smmu_master *master = dev_iommu_priv_get(dev);
+
+	/* Pre-allocate the CD leaf table without any locks held */
+	ret = arm_smmu_init_cd_table(master, id);
+	if (ret)
+		return ret;
 
 	mutex_lock(&sva_lock);
 	ret = __arm_smmu_sva_bind(dev, mm);
diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
index 0ffb1cf17e0b..e48f2b46f25e 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
@@ -1019,7 +1019,10 @@ static void arm_smmu_write_cd_l1_desc(__le64 *dst,
 	WRITE_ONCE(*dst, cpu_to_le64(val));
 }
 
-static __le64 *arm_smmu_get_cd_ptr(struct arm_smmu_master *master, u32 ssid)
+static __le64 *
+__arm_smmu_get_cd_ptr(struct arm_smmu_master *master, u32 ssid,
+		      int (*cd_alloc)(struct arm_smmu_device *,
+				      struct arm_smmu_l1_ctx_desc *))
 {
 	__le64 *l1ptr;
 	unsigned int idx;
@@ -1033,7 +1036,7 @@ static __le64 *arm_smmu_get_cd_ptr(struct arm_smmu_master *master, u32 ssid)
 	idx = ssid >> CTXDESC_SPLIT;
 	l1_desc = &cd_table->l1_desc[idx];
 	if (!l1_desc->l2ptr) {
-		if (arm_smmu_alloc_cd_leaf_table(smmu, l1_desc))
+		if (!cd_alloc || cd_alloc(smmu, l1_desc))
 			return NULL;
 
 		l1ptr = cd_table->cdtab + idx * CTXDESC_L1_DESC_DWORDS;
@@ -1045,6 +1048,19 @@ static __le64 *arm_smmu_get_cd_ptr(struct arm_smmu_master *master, u32 ssid)
 	return l1_desc->l2ptr + idx * CTXDESC_CD_DWORDS;
 }
 
+static __le64 *arm_smmu_get_cd_ptr(struct arm_smmu_master *master, u32 ssid)
+{
+	return __arm_smmu_get_cd_ptr(master, ssid, NULL);
+}
+
+int arm_smmu_init_cd_table(struct arm_smmu_master *master, int ssid)
+{
+	if (!__arm_smmu_get_cd_ptr(master, ssid, arm_smmu_alloc_cd_leaf_table))
+		return -ENOMEM;
+
+	return 0;
+}
+
 int arm_smmu_write_ctx_desc(struct arm_smmu_master *master, int ssid,
 			    struct arm_smmu_ctx_desc *cd)
 {
diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
index 65fb388d5173..cc42cede77bc 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
@@ -748,6 +748,7 @@ extern struct xarray arm_smmu_asid_xa;
 extern struct mutex arm_smmu_asid_lock;
 extern struct arm_smmu_ctx_desc quiet_cd;
 
+int arm_smmu_init_cd_table(struct arm_smmu_master *smmu_master, int ssid);
 int arm_smmu_write_ctx_desc(struct arm_smmu_master *smmu_master, int ssid,
 			    struct arm_smmu_ctx_desc *cd);
 void arm_smmu_tlb_inv_asid(struct arm_smmu_device *smmu, u16 asid);