From 989b762eb159473d2492b64d7c35cc2159c2bfe3 Mon Sep 17 00:00:00 2001 From: Georgi Djakov Date: Wed, 13 Oct 2021 11:11:07 -0700 Subject: [PATCH] FROMLIST: iommu/iova: Add support for IOVA max alignment tuning IOVAs are aligned to the smallest PAGE_SIZE order, where the requested IOVA can fit. But this might not work for all use-cases. It can cause IOVA fragmentation in some multimedia and 8K video use-cases that may require larger buffers to be allocated and mapped. When the above allocation pattern is used with the current alignment scheme, the IOVA space could be quickly exhausted for 32bit devices. In order to get better IOVA space utilization and reduce fragmentation, a new kernel command line parameter is introduced to make the alignment limit configurable by the user during boot. Bug: 190519428 Change-Id: I0c8e72370fc3266a5a242837d82aae4f9831aef3 Link: https://lore.kernel.org/r/1634148667-409263-1-git-send-email-quic_c_gdjako@quicinc.com/ Signed-off-by: Georgi Djakov --- .../admin-guide/kernel-parameters.txt | 8 +++++ drivers/iommu/iova.c | 29 ++++++++++++++++++- 2 files changed, 36 insertions(+), 1 deletion(-) diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index ab5b0a3ff0f9..112815dee3a9 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -2064,6 +2064,14 @@ forcing Dual Address Cycle for PCI cards supporting greater than 32-bit addressing. + iommu.max_align_shift= + [ARM64, X86] Limit the alignment of IOVAs to a maximum + PAGE_SIZE order. Larger IOVAs will be aligned to this + specified order. The order is expressed as a power of + two multiplied by the PAGE_SIZE. + Format: { "4" | "5" | "6" | "7" | "8" | "9" } + Default: 9 + iommu.strict= [ARM64, X86] Configure TLB invalidation behaviour Format: { "0" | "1" } 0 - Lazy mode. diff --git a/drivers/iommu/iova.c b/drivers/iommu/iova.c index 920fcc27c9a1..55aca4094072 100644 --- a/drivers/iommu/iova.c +++ b/drivers/iommu/iova.c @@ -5,6 +5,7 @@ * Author: Anil S Keshavamurthy */ +#include #include #include #include @@ -15,6 +16,9 @@ /* The anchor node sits above the top of the usable address space */ #define IOVA_ANCHOR ~0UL +#define IOMMU_DEFAULT_IOVA_MAX_ALIGN_SHIFT 9 +static unsigned long iommu_max_align_shift __read_mostly = IOMMU_DEFAULT_IOVA_MAX_ALIGN_SHIFT; + static bool iova_rcache_insert(struct iova_domain *iovad, unsigned long pfn, unsigned long size); @@ -27,6 +31,29 @@ static void free_iova_rcaches(struct iova_domain *iovad); static void fq_destroy_all_entries(struct iova_domain *iovad); static void fq_flush_timeout(struct timer_list *t); +static unsigned long limit_align_shift(struct iova_domain *iovad, unsigned long shift) +{ + unsigned long max_align_shift; + + max_align_shift = iommu_max_align_shift + PAGE_SHIFT - iova_shift(iovad); + return min_t(unsigned long, max_align_shift, shift); +} + +#ifndef MODULE +static int __init iommu_set_def_max_align_shift(char *str) +{ + unsigned long max_align_shift; + + int ret = kstrtoul(str, 10, &max_align_shift); + + if (!ret) + iommu_max_align_shift = max_align_shift; + + return 0; +} +early_param("iommu.max_align_shift", iommu_set_def_max_align_shift); +#endif + static int iova_cpuhp_dead(unsigned int cpu, struct hlist_node *node) { struct iova_domain *iovad; @@ -241,7 +268,7 @@ static int __alloc_and_insert_iova_range(struct iova_domain *iovad, unsigned long high_pfn = limit_pfn, low_pfn = iovad->start_pfn; if (size_aligned) - align_mask <<= fls_long(size - 1); + align_mask <<= limit_align_shift(iovad, fls_long(size - 1)); /* Walk the tree backwards */ spin_lock_irqsave(&iovad->iova_rbtree_lock, flags);