iommu/arm-smmu-v3: Change vmid alloc strategy from bitmap to ida

For current implementation of vmid allocation of arm smmu-v3, a per-smmu
devide bitmap of 64K bits(8K bytes) is allocated on behalf of possible VMID
range, which is two pages for some architectures. Besides that, its memory
consumption is 'static', despite of how many VMIDs are allocated actually.

That's memory inefficient and lack of scalability.

So an IDA based implementation is introduced to address this issue, which
is capable of self-expanding on the actual need of VMID allocation.

Signed-off-by: Dawei Li <set_pte_at@outlook.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Link: https://lore.kernel.org/r/TYCP286MB2323E0C525FF9F94E3B07C7ACA35A@TYCP286MB2323.JPNP286.PROD.OUTLOOK.COM
Signed-off-by: Will Deacon <will@kernel.org>

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 9b0dc35..d948760 100644 (file)
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
@@ -2055,24 +2055,6 @@ static struct iommu_domain *arm_smmu_domain_alloc(unsigned type)
        return &smmu_domain->domain;
 }
 
-static int arm_smmu_bitmap_alloc(unsigned long *map, int span)
-{
-       int idx, size = 1 << span;
-
-       do {
-               idx = find_first_zero_bit(map, size);
-               if (idx == size)
-                       return -ENOSPC;
-       } while (test_and_set_bit(idx, map));
-
-       return idx;
-}
-
-static void arm_smmu_bitmap_free(unsigned long *map, int idx)
-{
-       clear_bit(idx, map);
-}
-
 static void arm_smmu_domain_free(struct iommu_domain *domain)
 {
        struct arm_smmu_domain *smmu_domain = to_smmu_domain(domain);
@@ -2093,7 +2075,7 @@ static void arm_smmu_domain_free(struct iommu_domain *domain)
        } else {
                struct arm_smmu_s2_cfg *cfg = &smmu_domain->s2_cfg;
                if (cfg->vmid)
-                       arm_smmu_bitmap_free(smmu->vmid_map, cfg->vmid);
+                       ida_free(&smmu->vmid_map, cfg->vmid);
        }
 
        kfree(smmu_domain);
@@ -2167,7 +2149,9 @@ static int arm_smmu_domain_finalise_s2(struct arm_smmu_domain *smmu_domain,
        struct arm_smmu_s2_cfg *cfg = &smmu_domain->s2_cfg;
        typeof(&pgtbl_cfg->arm_lpae_s2_cfg.vtcr) vtcr;
 
-       vmid = arm_smmu_bitmap_alloc(smmu->vmid_map, smmu->vmid_bits);
+       /* Reserve VMID 0 for stage-2 bypass STEs */
+       vmid = ida_alloc_range(&smmu->vmid_map, 1, (1 << smmu->vmid_bits) - 1,
+                              GFP_KERNEL);
        if (vmid < 0)
                return vmid;
 
@@ -3098,8 +3082,8 @@ static int arm_smmu_init_strtab(struct arm_smmu_device *smmu)
        reg |= STRTAB_BASE_RA;
        smmu->strtab_cfg.strtab_base = reg;
 
-       /* Allocate the first VMID for stage-2 bypass STEs */
-       set_bit(0, smmu->vmid_map);
+       ida_init(&smmu->vmid_map);
+
        return 0;
 }
 
@@ -3923,6 +3907,7 @@ static void arm_smmu_device_remove(struct platform_device *pdev)
        iommu_device_sysfs_remove(&smmu->iommu);
        arm_smmu_device_disable(smmu);
        iopf_queue_free(smmu->evtq.iopf);
+       ida_destroy(&smmu->vmid_map);
 }
 
 static void arm_smmu_device_shutdown(struct platform_device *pdev)

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 dcab856..9915850 100644 (file)
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
@@ -670,7 +670,7 @@ struct arm_smmu_device {
 
 #define ARM_SMMU_MAX_VMIDS             (1 << 16)
        unsigned int                    vmid_bits;
-       DECLARE_BITMAP(vmid_map, ARM_SMMU_MAX_VMIDS);
+       struct ida                      vmid_map;
 
        unsigned int                    ssid_bits;
        unsigned int                    sid_bits;