Re: [PATCH v7 04/10] iommu/dma-reserved-iommu: alloc/free_reserved_iova_domain

From: Robin Murphy
Date: Wed Apr 20 2016 - 09:03:48 EST

On 19/04/16 17:56, Eric Auger wrote:
Introduce alloc/free_reserved_iova_domain in the IOMMU API.
alloc_reserved_iova_domain initializes an iova domain at a given
iova base address and with a given size. This iova domain will
be used to allocate iova within that window. Those IOVAs will be reserved
for special purpose, typically MSI frame binding. Allocation function
within the reserved iova domain will be introduced in subsequent patches.

Am I the only one thinking "Yo dawg, I heard you like IOVA allocators, so we put an IOVA allocator in your IOVA allocator so you can allocate IOVAs while you allocate IOVAs."

Those functions are fully implemented if CONFIG_IOMMU_DMA_RESERVED
is set.

DMA? I thought we were going to be dealing with MSI descriptors?

Signed-off-by: Eric Auger <eric.auger@xxxxxxxxxx>

---
v7:
- fix locking
- add iova_cache_get/put
- static inline functions when CONFIG_IOMMU_DMA_RESERVED is not set
- introduce struct reserved_iova_domain to encapsulate prot info &
add prot parameter in alloc_reserved_iova_domain

v5 -> v6:
- use spin lock instead of mutex

v3 -> v4:
- formerly in "iommu/arm-smmu: implement alloc/free_reserved_iova_domain" &
"iommu: add alloc/free_reserved_iova_domain"

v2 -> v3:
- remove iommu_alloc_reserved_iova_domain & iommu_free_reserved_iova_domain
static implementation in case CONFIG_IOMMU_API is not set

v1 -> v2:
- moved from vfio API to IOMMU API
---
drivers/iommu/Kconfig | 8 +++
drivers/iommu/Makefile | 1 +
drivers/iommu/dma-reserved-iommu.c | 99 ++++++++++++++++++++++++++++++++++++++
include/linux/dma-reserved-iommu.h | 59 +++++++++++++++++++++++
4 files changed, 167 insertions(+)
create mode 100644 drivers/iommu/dma-reserved-iommu.c
create mode 100644 include/linux/dma-reserved-iommu.h

diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig
index dd1dc39..a5a1530 100644
--- a/drivers/iommu/Kconfig
+++ b/drivers/iommu/Kconfig
@@ -74,6 +74,12 @@ config IOMMU_DMA
select IOMMU_IOVA
select NEED_SG_DMA_LENGTH

+# IOMMU reserved IOVA mapping (MSI doorbell)

The only reference to MSIs I can see, but I can't make head nor tail of it. Sorry, I don't understand this patch at all :(

Robin.

+config IOMMU_DMA_RESERVED
+ bool
+ select IOMMU_API
+ select IOMMU_IOVA
+
config FSL_PAMU
bool "Freescale IOMMU support"
depends on PPC32
@@ -307,6 +313,7 @@ config SPAPR_TCE_IOMMU
config ARM_SMMU
bool "ARM Ltd. System MMU (SMMU) Support"
depends on (ARM64 || ARM) && MMU
+ select IOMMU_DMA_RESERVED
select IOMMU_API
select IOMMU_IO_PGTABLE_LPAE
select ARM_DMA_USE_IOMMU if ARM
@@ -320,6 +327,7 @@ config ARM_SMMU
config ARM_SMMU_V3
bool "ARM Ltd. System MMU Version 3 (SMMUv3) Support"
depends on ARM64 && PCI
+ select IOMMU_DMA_RESERVED
select IOMMU_API
select IOMMU_IO_PGTABLE_LPAE
select GENERIC_MSI_IRQ_DOMAIN
diff --git a/drivers/iommu/Makefile b/drivers/iommu/Makefile
index c6edb31..6c9ae99 100644
--- a/drivers/iommu/Makefile
+++ b/drivers/iommu/Makefile
@@ -2,6 +2,7 @@ obj-$(CONFIG_IOMMU_API) += iommu.o
obj-$(CONFIG_IOMMU_API) += iommu-traces.o
obj-$(CONFIG_IOMMU_API) += iommu-sysfs.o
obj-$(CONFIG_IOMMU_DMA) += dma-iommu.o
+obj-$(CONFIG_IOMMU_DMA_RESERVED) += dma-reserved-iommu.o
obj-$(CONFIG_IOMMU_IO_PGTABLE) += io-pgtable.o
obj-$(CONFIG_IOMMU_IO_PGTABLE_ARMV7S) += io-pgtable-arm-v7s.o
obj-$(CONFIG_IOMMU_IO_PGTABLE_LPAE) += io-pgtable-arm.o
diff --git a/drivers/iommu/dma-reserved-iommu.c b/drivers/iommu/dma-reserved-iommu.c
new file mode 100644
index 0000000..2562af0
--- /dev/null
+++ b/drivers/iommu/dma-reserved-iommu.c
@@ -0,0 +1,99 @@
+/*
+ * Reserved IOVA Management
+ *
+ * Copyright (c) 2015 Linaro Ltd.
+ * www.linaro.org
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ */
+
+#include <linux/iommu.h>
+#include <linux/iova.h>
+
+struct reserved_iova_domain {
+ struct iova_domain *iovad;
+ int prot; /* iommu protection attributes to be obeyed */
+};
+
+int iommu_alloc_reserved_iova_domain(struct iommu_domain *domain,
+ dma_addr_t iova, size_t size, int prot,
+ unsigned long order)
+{
+ unsigned long granule, mask, flags;
+ struct reserved_iova_domain *rid;
+ int ret = 0;
+
+ granule = 1UL << order;
+ mask = granule - 1;
+ if (iova & mask || (!size) || (size & mask))
+ return -EINVAL;
+
+ rid = kzalloc(sizeof(struct reserved_iova_domain), GFP_KERNEL);
+ if (!rid)
+ return -ENOMEM;
+
+ rid->iovad = kzalloc(sizeof(struct iova_domain), GFP_KERNEL);
+ if (!rid->iovad) {
+ kfree(rid);
+ return -ENOMEM;
+ }
+
+ iova_cache_get();
+
+ init_iova_domain(rid->iovad, granule,
+ iova >> order, (iova + size - 1) >> order);
+
+ spin_lock_irqsave(&domain->reserved_lock, flags);
+
+ if (domain->reserved_iova_cookie) {
+ ret = -EEXIST;
+ goto unlock;
+ }
+
+ domain->reserved_iova_cookie = rid;
+
+unlock:
+ spin_unlock_irqrestore(&domain->reserved_lock, flags);
+ if (ret) {
+ put_iova_domain(rid->iovad);
+ kfree(rid->iovad);
+ kfree(rid);
+ iova_cache_put();
+ }
+ return ret;
+}
+EXPORT_SYMBOL_GPL(iommu_alloc_reserved_iova_domain);
+
+void iommu_free_reserved_iova_domain(struct iommu_domain *domain)
+{
+ struct reserved_iova_domain *rid;
+ unsigned long flags;
+ int ret = 0;
+
+ spin_lock_irqsave(&domain->reserved_lock, flags);
+
+ rid = (struct reserved_iova_domain *)domain->reserved_iova_cookie;
+ if (!rid) {
+ ret = -EINVAL;
+ goto unlock;
+ }
+
+ domain->reserved_iova_cookie = NULL;
+unlock:
+ spin_unlock_irqrestore(&domain->reserved_lock, flags);
+ if (!ret) {
+ put_iova_domain(rid->iovad);
+ kfree(rid->iovad);
+ kfree(rid);
+ iova_cache_put();
+ }
+}
+EXPORT_SYMBOL_GPL(iommu_free_reserved_iova_domain);
diff --git a/include/linux/dma-reserved-iommu.h b/include/linux/dma-reserved-iommu.h
new file mode 100644
index 0000000..01ec385
--- /dev/null
+++ b/include/linux/dma-reserved-iommu.h
@@ -0,0 +1,59 @@
+/*
+ * Copyright (c) 2015 Linaro Ltd.
+ * www.linaro.org
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ */
+#ifndef __DMA_RESERVED_IOMMU_H
+#define __DMA_RESERVED_IOMMU_H
+
+#include <linux/types.h>
+#include <linux/kernel.h>
+
+struct iommu_domain;
+
+#ifdef CONFIG_IOMMU_DMA_RESERVED
+
+/**
+ * iommu_alloc_reserved_iova_domain: allocate the reserved iova domain
+ *
+ * @domain: iommu domain handle
+ * @iova: base iova address
+ * @size: iova window size
+ * @prot: protection attribute flags
+ * @order: page order
+ */
+int iommu_alloc_reserved_iova_domain(struct iommu_domain *domain,
+ dma_addr_t iova, size_t size, int prot,
+ unsigned long order);
+
+/**
+ * iommu_free_reserved_iova_domain: free the reserved iova domain
+ *
+ * @domain: iommu domain handle
+ */
+void iommu_free_reserved_iova_domain(struct iommu_domain *domain);
+
+#else
+
+static inline int
+iommu_alloc_reserved_iova_domain(struct iommu_domain *domain,
+ dma_addr_t iova, size_t size, int prot,
+ unsigned long order)
+{
+ return -ENOENT;
+}
+
+static inline void
+iommu_free_reserved_iova_domain(struct iommu_domain *domain) {}
+
+#endif /* CONFIG_IOMMU_DMA_RESERVED */
+#endif /* __DMA_RESERVED_IOMMU_H */