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Message-ID: <63888cd2-dfbd-ecad-abe2-9426fa61e72c@caviumnetworks.com>
Date: Tue, 17 Jan 2017 12:59:02 +0100
From: Tomasz Nowicki <tnowicki@...iumnetworks.com>
To: Eric Auger <eric.auger@...hat.com>, <eric.auger.pro@...il.com>,
<christoffer.dall@...aro.org>, <marc.zyngier@....com>,
<robin.murphy@....com>, <alex.williamson@...hat.com>,
<will.deacon@....com>, <joro@...tes.org>, <tglx@...utronix.de>,
<jason@...edaemon.net>, <linux-arm-kernel@...ts.infradead.org>
CC: <drjones@...hat.com>, <kvm@...r.kernel.org>,
<punit.agrawal@....com>, <linux-kernel@...r.kernel.org>,
<geethasowjanya.akula@...il.com>, <diana.craciun@....com>,
<iommu@...ts.linux-foundation.org>,
<pranav.sawargaonkar@...il.com>, <bharat.bhushan@....com>,
<shankerd@...eaurora.org>, <gpkulkarni@...il.com>
Subject: Re: [PATCH v8 01/18] iommu/dma: Allow MSI-only cookies
On 11.01.2017 10:41, Eric Auger wrote:
> From: Robin Murphy <robin.murphy@....com>
>
> IOMMU domain users such as VFIO face a similar problem to DMA API ops
> with regard to mapping MSI messages in systems where the MSI write is
> subject to IOMMU translation. With the relevant infrastructure now in
> place for managed DMA domains, it's actually really simple for other
> users to piggyback off that and reap the benefits without giving up
> their own IOVA management, and without having to reinvent their own
> wheel in the MSI layer.
>
> Allow such users to opt into automatic MSI remapping by dedicating a
> region of their IOVA space to a managed cookie, and extend the mapping
> routine to implement a trivial linear allocator in such cases, to avoid
> the needless overhead of a full-blown IOVA domain.
>
> Signed-off-by: Robin Murphy <robin.murphy@....com>
Reviewed-by: Tomasz Nowicki <tomasz.nowicki@...iumnetworks.com>
Thanks,
Tomasz
> ---
> drivers/iommu/dma-iommu.c | 119 +++++++++++++++++++++++++++++++++++++---------
> include/linux/dma-iommu.h | 6 +++
> 2 files changed, 102 insertions(+), 23 deletions(-)
>
> diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
> index 2db0d64..de41ead 100644
> --- a/drivers/iommu/dma-iommu.c
> +++ b/drivers/iommu/dma-iommu.c
> @@ -37,15 +37,50 @@ struct iommu_dma_msi_page {
> phys_addr_t phys;
> };
>
> +enum iommu_dma_cookie_type {
> + IOMMU_DMA_IOVA_COOKIE,
> + IOMMU_DMA_MSI_COOKIE,
> +};
> +
> struct iommu_dma_cookie {
> - struct iova_domain iovad;
> - struct list_head msi_page_list;
> - spinlock_t msi_lock;
> + enum iommu_dma_cookie_type type;
> + union {
> + /* Full allocator for IOMMU_DMA_IOVA_COOKIE */
> + struct iova_domain iovad;
> + /* Trivial linear page allocator for IOMMU_DMA_MSI_COOKIE */
> + dma_addr_t msi_iova;
> + };
> + struct list_head msi_page_list;
> + spinlock_t msi_lock;
> };
>
> +static inline size_t cookie_msi_granule(struct iommu_dma_cookie *cookie)
> +{
> + if (cookie->type == IOMMU_DMA_IOVA_COOKIE)
> + return cookie->iovad.granule;
> + return PAGE_SIZE;
> +}
> +
> static inline struct iova_domain *cookie_iovad(struct iommu_domain *domain)
> {
> - return &((struct iommu_dma_cookie *)domain->iova_cookie)->iovad;
> + struct iommu_dma_cookie *cookie = domain->iova_cookie;
> +
> + if (cookie->type == IOMMU_DMA_IOVA_COOKIE)
> + return &cookie->iovad;
> + return NULL;
> +}
> +
> +static struct iommu_dma_cookie *cookie_alloc(enum iommu_dma_cookie_type type)
> +{
> + struct iommu_dma_cookie *cookie;
> +
> + cookie = kzalloc(sizeof(*cookie), GFP_KERNEL);
> + if (cookie) {
> + spin_lock_init(&cookie->msi_lock);
> + INIT_LIST_HEAD(&cookie->msi_page_list);
> + cookie->type = type;
> + }
> + return cookie;
> }
>
> int iommu_dma_init(void)
> @@ -62,25 +97,53 @@ int iommu_dma_init(void)
> */
> int iommu_get_dma_cookie(struct iommu_domain *domain)
> {
> + if (domain->iova_cookie)
> + return -EEXIST;
> +
> + domain->iova_cookie = cookie_alloc(IOMMU_DMA_IOVA_COOKIE);
> + if (!domain->iova_cookie)
> + return -ENOMEM;
> +
> + return 0;
> +}
> +EXPORT_SYMBOL(iommu_get_dma_cookie);
> +
> +/**
> + * iommu_get_msi_cookie - Acquire just MSI remapping resources
> + * @domain: IOMMU domain to prepare
> + * @base: Start address of IOVA region for MSI mappings
> + *
> + * Users who manage their own IOVA allocation and do not want DMA API support,
> + * but would still like to take advantage of automatic MSI remapping, can use
> + * this to initialise their own domain appropriately. Users should reserve a
> + * contiguous IOVA region, starting at @base, large enough to accommodate the
> + * number of PAGE_SIZE mappings necessary to cover every MSI doorbell address
> + * used by the devices attached to @domain.
> + */
> +int iommu_get_msi_cookie(struct iommu_domain *domain, dma_addr_t base)
> +{
> struct iommu_dma_cookie *cookie;
>
> + if (domain->type != IOMMU_DOMAIN_UNMANAGED)
> + return -EINVAL;
> +
> if (domain->iova_cookie)
> return -EEXIST;
>
> - cookie = kzalloc(sizeof(*cookie), GFP_KERNEL);
> + cookie = cookie_alloc(IOMMU_DMA_MSI_COOKIE);
> if (!cookie)
> return -ENOMEM;
>
> - spin_lock_init(&cookie->msi_lock);
> - INIT_LIST_HEAD(&cookie->msi_page_list);
> + cookie->msi_iova = base;
> domain->iova_cookie = cookie;
> return 0;
> }
> -EXPORT_SYMBOL(iommu_get_dma_cookie);
> +EXPORT_SYMBOL(iommu_get_msi_cookie);
>
> /**
> * iommu_put_dma_cookie - Release a domain's DMA mapping resources
> - * @domain: IOMMU domain previously prepared by iommu_get_dma_cookie()
> + * @domain: IOMMU domain previously prepared by iommu_get_dma_cookie() or
> + * iommu_get_msi_cookie()
> *
> * IOMMU drivers should normally call this from their domain_free callback.
> */
> @@ -92,7 +155,7 @@ void iommu_put_dma_cookie(struct iommu_domain *domain)
> if (!cookie)
> return;
>
> - if (cookie->iovad.granule)
> + if (cookie->type == IOMMU_DMA_IOVA_COOKIE && cookie->iovad.granule)
> put_iova_domain(&cookie->iovad);
>
> list_for_each_entry_safe(msi, tmp, &cookie->msi_page_list, list) {
> @@ -137,11 +200,12 @@ static void iova_reserve_pci_windows(struct pci_dev *dev,
> int iommu_dma_init_domain(struct iommu_domain *domain, dma_addr_t base,
> u64 size, struct device *dev)
> {
> - struct iova_domain *iovad = cookie_iovad(domain);
> + struct iommu_dma_cookie *cookie = domain->iova_cookie;
> + struct iova_domain *iovad = &cookie->iovad;
> unsigned long order, base_pfn, end_pfn;
>
> - if (!iovad)
> - return -ENODEV;
> + if (!cookie || cookie->type != IOMMU_DMA_IOVA_COOKIE)
> + return -EINVAL;
>
> /* Use the smallest supported page size for IOVA granularity */
> order = __ffs(domain->pgsize_bitmap);
> @@ -662,11 +726,12 @@ static struct iommu_dma_msi_page *iommu_dma_get_msi_page(struct device *dev,
> {
> struct iommu_dma_cookie *cookie = domain->iova_cookie;
> struct iommu_dma_msi_page *msi_page;
> - struct iova_domain *iovad = &cookie->iovad;
> + struct iova_domain *iovad = cookie_iovad(domain);
> struct iova *iova;
> int prot = IOMMU_WRITE | IOMMU_NOEXEC | IOMMU_MMIO;
> + size_t size = cookie_msi_granule(cookie);
>
> - msi_addr &= ~(phys_addr_t)iova_mask(iovad);
> + msi_addr &= ~(phys_addr_t)(size - 1);
> list_for_each_entry(msi_page, &cookie->msi_page_list, list)
> if (msi_page->phys == msi_addr)
> return msi_page;
> @@ -675,13 +740,18 @@ static struct iommu_dma_msi_page *iommu_dma_get_msi_page(struct device *dev,
> if (!msi_page)
> return NULL;
>
> - iova = __alloc_iova(domain, iovad->granule, dma_get_mask(dev));
> - if (!iova)
> - goto out_free_page;
> -
> msi_page->phys = msi_addr;
> - msi_page->iova = iova_dma_addr(iovad, iova);
> - if (iommu_map(domain, msi_page->iova, msi_addr, iovad->granule, prot))
> + if (iovad) {
> + iova = __alloc_iova(domain, size, dma_get_mask(dev));
> + if (!iova)
> + goto out_free_page;
> + msi_page->iova = iova_dma_addr(iovad, iova);
> + } else {
> + msi_page->iova = cookie->msi_iova;
> + cookie->msi_iova += size;
> + }
> +
> + if (iommu_map(domain, msi_page->iova, msi_addr, size, prot))
> goto out_free_iova;
>
> INIT_LIST_HEAD(&msi_page->list);
> @@ -689,7 +759,10 @@ static struct iommu_dma_msi_page *iommu_dma_get_msi_page(struct device *dev,
> return msi_page;
>
> out_free_iova:
> - __free_iova(iovad, iova);
> + if (iovad)
> + __free_iova(iovad, iova);
> + else
> + cookie->msi_iova -= size;
> out_free_page:
> kfree(msi_page);
> return NULL;
> @@ -730,7 +803,7 @@ void iommu_dma_map_msi_msg(int irq, struct msi_msg *msg)
> msg->data = ~0U;
> } else {
> msg->address_hi = upper_32_bits(msi_page->iova);
> - msg->address_lo &= iova_mask(&cookie->iovad);
> + msg->address_lo &= cookie_msi_granule(cookie) - 1;
> msg->address_lo += lower_32_bits(msi_page->iova);
> }
> }
> diff --git a/include/linux/dma-iommu.h b/include/linux/dma-iommu.h
> index 7f7e9a7..28df844 100644
> --- a/include/linux/dma-iommu.h
> +++ b/include/linux/dma-iommu.h
> @@ -27,6 +27,7 @@
>
> /* Domain management interface for IOMMU drivers */
> int iommu_get_dma_cookie(struct iommu_domain *domain);
> +int iommu_get_msi_cookie(struct iommu_domain *domain, dma_addr_t base);
> void iommu_put_dma_cookie(struct iommu_domain *domain);
>
> /* Setup call for arch DMA mapping code */
> @@ -86,6 +87,11 @@ static inline int iommu_get_dma_cookie(struct iommu_domain *domain)
> return -ENODEV;
> }
>
> +static inline int iommu_get_msi_cookie(struct iommu_domain *domain, dma_addr_t base)
> +{
> + return -ENODEV;
> +}
> +
> static inline void iommu_put_dma_cookie(struct iommu_domain *domain)
> {
> }
>
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