linux-kernel - [PATCH v6 3/7] iommu/io-pgtable-arm: Add support for non-strict mode

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Date:   Thu, 13 Sep 2018 17:42:20 +0100
From:   Robin Murphy <robin.murphy@....com>
To:     joro@...tes.org, will.deacon@....com, thunder.leizhen@...wei.com,
        iommu@...ts.linux-foundation.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Cc:     linuxarm@...wei.com, guohanjun@...wei.com, huawei.libin@...wei.com,
        john.garry@...wei.com
Subject: [PATCH v6 3/7] iommu/io-pgtable-arm: Add support for non-strict mode

From: Zhen Lei <thunder.leizhen@...wei.com>

To support non-strict mode, now we only TLBI and sync for strict mode,
except for non-leaf invalidations since page table updates themselves
must always be synchronous.

To save having to reason about it too much, make sure the invalidation
in arm_lpae_split_blk_unmap() just performs its own unconditional sync
to minimise the window in which we're technically violating the break-
before-make requirement on a live mapping. This might work out redundant
with an outer-level sync for strict unmaps, but we'll never be splitting
blocks on a DMA fastpath anyway.

Signed-off-by: Zhen Lei <thunder.leizhen@...wei.com>
[rm: tweak comment, commit message, and split_blk_unmap logic]
Signed-off-by: Robin Murphy <robin.murphy@....com>
---
 drivers/iommu/io-pgtable-arm.c | 9 ++++++---
 drivers/iommu/io-pgtable.h     | 5 +++++
 2 files changed, 11 insertions(+), 3 deletions(-)

diff --git a/drivers/iommu/io-pgtable-arm.c b/drivers/iommu/io-pgtable-arm.c
index 2f79efd16a05..5b915aab7fd3 100644
--- a/drivers/iommu/io-pgtable-arm.c
+++ b/drivers/iommu/io-pgtable-arm.c
@@ -576,6 +576,7 @@ static size_t arm_lpae_split_blk_unmap(struct arm_lpae_io_pgtable *data,
 		tablep = iopte_deref(pte, data);
 	} else if (unmap_idx >= 0) {
 		io_pgtable_tlb_add_flush(&data->iop, iova, size, size, true);
+		io_pgtable_tlb_sync(&data->iop);
 		return size;
 	}
 
@@ -609,7 +610,7 @@ static size_t __arm_lpae_unmap(struct arm_lpae_io_pgtable *data,
 			io_pgtable_tlb_sync(iop);
 			ptep = iopte_deref(pte, data);
 			__arm_lpae_free_pgtable(data, lvl + 1, ptep);
-		} else {
+		} else if (!(iop->cfg.quirks & IO_PGTABLE_QUIRK_NON_STRICT)) {
 			io_pgtable_tlb_add_flush(iop, iova, size, size, true);
 		}
 
@@ -771,7 +772,8 @@ arm_64_lpae_alloc_pgtable_s1(struct io_pgtable_cfg *cfg, void *cookie)
 	u64 reg;
 	struct arm_lpae_io_pgtable *data;
 
-	if (cfg->quirks & ~(IO_PGTABLE_QUIRK_ARM_NS | IO_PGTABLE_QUIRK_NO_DMA))
+	if (cfg->quirks & ~(IO_PGTABLE_QUIRK_ARM_NS | IO_PGTABLE_QUIRK_NO_DMA |
+			    IO_PGTABLE_QUIRK_NON_STRICT))
 		return NULL;
 
 	data = arm_lpae_alloc_pgtable(cfg);
@@ -863,7 +865,8 @@ arm_64_lpae_alloc_pgtable_s2(struct io_pgtable_cfg *cfg, void *cookie)
 	struct arm_lpae_io_pgtable *data;
 
 	/* The NS quirk doesn't apply at stage 2 */
-	if (cfg->quirks & ~IO_PGTABLE_QUIRK_NO_DMA)
+	if (cfg->quirks & ~(IO_PGTABLE_QUIRK_NO_DMA |
+			    IO_PGTABLE_QUIRK_NON_STRICT))
 		return NULL;
 
 	data = arm_lpae_alloc_pgtable(cfg);
diff --git a/drivers/iommu/io-pgtable.h b/drivers/iommu/io-pgtable.h
index 2df79093cad9..47d5ae559329 100644
--- a/drivers/iommu/io-pgtable.h
+++ b/drivers/iommu/io-pgtable.h
@@ -71,12 +71,17 @@ struct io_pgtable_cfg {
 	 *	be accessed by a fully cache-coherent IOMMU or CPU (e.g. for a
 	 *	software-emulated IOMMU), such that pagetable updates need not
 	 *	be treated as explicit DMA data.
+	 *
+	 * IO_PGTABLE_QUIRK_NON_STRICT: Skip issuing synchronous leaf TLBIs
+	 *	on unmap, for DMA domains using the flush queue mechanism for
+	 *	delayed invalidation.
 	 */
 	#define IO_PGTABLE_QUIRK_ARM_NS		BIT(0)
 	#define IO_PGTABLE_QUIRK_NO_PERMS	BIT(1)
 	#define IO_PGTABLE_QUIRK_TLBI_ON_MAP	BIT(2)
 	#define IO_PGTABLE_QUIRK_ARM_MTK_4GB	BIT(3)
 	#define IO_PGTABLE_QUIRK_NO_DMA		BIT(4)
+	#define IO_PGTABLE_QUIRK_NON_STRICT	BIT(5)
 	unsigned long			quirks;
 	unsigned long			pgsize_bitmap;
 	unsigned int			ias;
-- 
2.19.0.dirty