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Message-ID: <20160406170021.4087a955@t450s.home>
Date: Wed, 6 Apr 2016 17:00:21 -0600
From: Alex Williamson <alex.williamson@...hat.com>
To: Eric Auger <eric.auger@...aro.org>
Cc: eric.auger@...com, robin.murphy@....com, will.deacon@....com,
joro@...tes.org, tglx@...utronix.de, jason@...edaemon.net,
marc.zyngier@....com, christoffer.dall@...aro.org,
linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.cs.columbia.edu,
kvm@...r.kernel.org, suravee.suthikulpanit@....com,
patches@...aro.org, linux-kernel@...r.kernel.org,
Manish.Jaggi@...iumnetworks.com, Bharat.Bhushan@...escale.com,
pranav.sawargaonkar@...il.com, p.fedin@...sung.com,
iommu@...ts.linux-foundation.org, Jean-Philippe.Brucker@....com,
julien.grall@....com
Subject: Re: [PATCH v6 4/7] dma-reserved-iommu:
alloc/free_reserved_iova_domain
On Mon, 4 Apr 2016 08:06:59 +0000
Eric Auger <eric.auger@...aro.org> 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.
>
> Those functions are implemented and exposed if CONFIG_IOMMU_DMA_RESERVED
> is seta.
>
> Signed-off-by: Eric Auger <eric.auger@...aro.org>
>
> ---
>
> 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 | 75 ++++++++++++++++++++++++++++++++++++++
> include/linux/dma-reserved-iommu.h | 45 +++++++++++++++++++++++
> 4 files changed, 129 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)
> +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..a461482
> --- /dev/null
> +++ b/drivers/iommu/dma-reserved-iommu.c
> @@ -0,0 +1,75 @@
> +/*
> + * 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>
> +
> +int iommu_alloc_reserved_iova_domain(struct iommu_domain *domain,
> + dma_addr_t iova, size_t size,
> + unsigned long order)
> +{
> + unsigned long granule, mask;
> + struct iova_domain *iovad;
> + unsigned long flags;
> + int ret = 0;
> +
> + granule = 1UL << order;
> + mask = granule - 1;
> + if (iova & mask || (!size) || (size & mask))
> + return -EINVAL;
> +
> + iovad = kzalloc(sizeof(struct iova_domain), GFP_KERNEL);
> + if (!iovad)
> + return -ENOMEM;
> +
> + spin_lock_irqsave(&domain->reserved_lock, flags);
> +
> + if (domain->reserved_iova_cookie) {
> + ret = -EEXIST;
> + goto free_unlock;
> + }
> +
> + init_iova_domain(iovad, granule,
> + iova >> order, (iova + size - 1) >> order);
> + domain->reserved_iova_cookie = iovad;
> + goto unlock;
> +
> +free_unlock:
> + kfree(iovad);
> +unlock:
> + spin_unlock_irqrestore(&domain->reserved_lock, flags);
> + return ret;
> +}
> +EXPORT_SYMBOL_GPL(iommu_alloc_reserved_iova_domain);
> +
> +void iommu_free_reserved_iova_domain(struct iommu_domain *domain)
> +{
> + struct iova_domain *iovad =
> + (struct iova_domain *)domain->reserved_iova_cookie;
> + unsigned long flags;
> +
> + if (!iovad)
> + return;
> +
> + spin_lock_irqsave(&domain->reserved_lock, flags);
> +
> + put_iova_domain(iovad);
> + kfree(iovad);
> +
> + spin_unlock_irqrestore(&domain->reserved_lock, flags);
> +}
The locking here looks wrong, reserved_iova_cookie needs to be read and
cleared (currently missing) within the lock, the put and free can
probably happen outside the lock. Likewise the init_iova_domain() in
the alloc path probably doesn't need to iccur under spinlock, but
testing and setting reserved_iova_cookie does. Seems like a mutex
would do for locking here, but maybe the rb-tree manipulation has
reasons for using a spinlock. Thanks,
Alex
> +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..5bf863b
> --- /dev/null
> +++ b/include/linux/dma-reserved-iommu.h
> @@ -0,0 +1,45 @@
> +/*
> + * 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
> +
> +#ifdef __KERNEL__
> +#include <asm/errno.h>
> +
> +#ifdef CONFIG_IOMMU_DMA_RESERVED
> +#include <linux/iommu.h>
> +
> +/**
> + * iommu_alloc_reserved_iova_domain: allocate the reserved iova domain
> + *
> + * @domain: iommu domain handle
> + * @iova: base iova address
> + * @size: iova window size
> + * @order: page order
> + */
> +int iommu_alloc_reserved_iova_domain(struct iommu_domain *domain,
> + dma_addr_t iova, size_t size,
> + 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);
> +
> +#endif /* CONFIG_IOMMU_DMA_RESERVED */
> +#endif /* __KERNEL__ */
> +#endif /* __DMA_RESERVED_IOMMU_H */
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