Messages in this thread | | | Subject | Re: [RFC v2 12/20] dma-iommu: Implement NESTED_MSI cookie | From | Robin Murphy <> | Date | Wed, 24 Oct 2018 19:02:59 +0100 |
| |
Hi Eric,
On 2018-09-18 3:24 pm, Eric Auger wrote: > Up to now, when the type was UNMANAGED, we used to > allocate IOVA pages within a range provided by the user. > This does not work in nested mode. > > If both the host and the guest are exposed with SMMUs, each > would allocate an IOVA. The guest allocates an IOVA (gIOVA) > to map onto the guest MSI doorbell (gDB). The Host allocates > another IOVA (hIOVA) to map onto the physical doorbell (hDB). > > So we end up with 2 unrelated mappings, at S1 and S2: > S1 S2 > gIOVA -> gDB > hIOVA -> hDB > > The PCI device would be programmed with hIOVA. > > iommu_dma_bind_doorbell allows to pass gIOVA/gDB to the host > so that gIOVA can be used by the host instead of re-allocating > a new IOVA. That way the host can create the following nested > mapping: > > S1 S2 > gIOVA -> gDB -> hDB > > this time, the PCI device will be programmed with the gIOVA MSI > doorbell which is correctly map through the 2 stages.
If I'm understanding things correctly, this plus a couple of the preceding patches all add up to a rather involved way of coercing an automatic allocator to only "allocate" predetermined addresses in an entirely known-ahead-of-time manner. Given that the guy calling iommu_dma_bind_doorbell() could seemingly just as easily call iommu_map() at that point and not bother with an allocator cookie and all this machinery at all, what am I missing?
Robin.
> > Signed-off-by: Eric Auger <eric.auger@redhat.com> > > --- > > v1 -> v2: > - unmap stage2 on put() > --- > drivers/iommu/dma-iommu.c | 97 +++++++++++++++++++++++++++++++++++++-- > include/linux/dma-iommu.h | 11 +++++ > 2 files changed, 105 insertions(+), 3 deletions(-) > > diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c > index 511ff9a1d6d9..53444c3e8f2f 100644 > --- a/drivers/iommu/dma-iommu.c > +++ b/drivers/iommu/dma-iommu.c > @@ -37,12 +37,14 @@ > struct iommu_dma_msi_page { > struct list_head list; > dma_addr_t iova; > + dma_addr_t ipa; > phys_addr_t phys; > }; > > enum iommu_dma_cookie_type { > IOMMU_DMA_IOVA_COOKIE, > IOMMU_DMA_MSI_COOKIE, > + IOMMU_DMA_NESTED_MSI_COOKIE, > }; > > struct iommu_dma_cookie { > @@ -109,14 +111,17 @@ EXPORT_SYMBOL(iommu_get_dma_cookie); > * > * 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 > + * this to initialise their own domain appropriately. Users may 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. > + * used by the devices attached to @domain. The other way round is to provide > + * usable iova pages through the iommu_dma_bind_doorbell API (nested stages > + * use case) > */ > int iommu_get_msi_cookie(struct iommu_domain *domain, dma_addr_t base) > { > struct iommu_dma_cookie *cookie; > + int nesting, ret; > > if (domain->type != IOMMU_DOMAIN_UNMANAGED) > return -EINVAL; > @@ -124,7 +129,12 @@ int iommu_get_msi_cookie(struct iommu_domain *domain, dma_addr_t base) > if (domain->iova_cookie) > return -EEXIST; > > - cookie = cookie_alloc(IOMMU_DMA_MSI_COOKIE); > + ret = iommu_domain_get_attr(domain, DOMAIN_ATTR_NESTING, &nesting); > + if (!ret && nesting) > + cookie = cookie_alloc(IOMMU_DMA_NESTED_MSI_COOKIE); > + else > + cookie = cookie_alloc(IOMMU_DMA_MSI_COOKIE); > + > if (!cookie) > return -ENOMEM; > > @@ -145,6 +155,7 @@ void iommu_put_dma_cookie(struct iommu_domain *domain) > { > struct iommu_dma_cookie *cookie = domain->iova_cookie; > struct iommu_dma_msi_page *msi, *tmp; > + bool s2_unmap = false; > > if (!cookie) > return; > @@ -152,7 +163,15 @@ void iommu_put_dma_cookie(struct iommu_domain *domain) > if (cookie->type == IOMMU_DMA_IOVA_COOKIE && cookie->iovad.granule) > put_iova_domain(&cookie->iovad); > > + if (cookie->type == IOMMU_DMA_NESTED_MSI_COOKIE) > + s2_unmap = true; > + > list_for_each_entry_safe(msi, tmp, &cookie->msi_page_list, list) { > + if (s2_unmap && msi->phys) { > + size_t size = cookie_msi_granule(cookie); > + > + WARN_ON(iommu_unmap(domain, msi->ipa, size) != size); > + } > list_del(&msi->list); > kfree(msi); > } > @@ -161,6 +180,50 @@ void iommu_put_dma_cookie(struct iommu_domain *domain) > } > EXPORT_SYMBOL(iommu_put_dma_cookie); > > +/** > + * iommu_dma_bind_doorbell - Allows to provide a usable IOVA page > + * @domain: domain handle > + * @binding: IOVA/IPA binding > + * > + * In nested stage use case, the user can provide IOVA/IPA bindings > + * corresponding to a guest MSI stage 1 mapping. When the host needs > + * to map its own MSI doorbells, it can use the IPA as stage 2 input > + * and map it onto the physical MSI doorbell. > + */ > +int iommu_dma_bind_doorbell(struct iommu_domain *domain, > + struct iommu_guest_msi_binding *binding) > +{ > + struct iommu_dma_cookie *cookie = domain->iova_cookie; > + struct iommu_dma_msi_page *msi; > + dma_addr_t ipa, iova; > + size_t size; > + > + if (!cookie) > + return -EINVAL; > + > + if (cookie->type != IOMMU_DMA_NESTED_MSI_COOKIE) > + return -EINVAL; > + > + size = 1 << binding->granule; > + iova = binding->iova & ~(phys_addr_t)(size - 1); > + ipa = binding->gpa & ~(phys_addr_t)(size - 1); > + > + list_for_each_entry(msi, &cookie->msi_page_list, list) { > + if (msi->iova == iova) > + return 0; /* this page is already registered */ > + } > + > + msi = kzalloc(sizeof(*msi), GFP_KERNEL); > + if (!msi) > + return -ENOMEM; > + > + msi->iova = iova; > + msi->ipa = ipa; > + list_add(&msi->list, &cookie->msi_page_list); > + return 0; > +} > +EXPORT_SYMBOL(iommu_dma_bind_doorbell); > + > /** > * iommu_dma_get_resv_regions - Reserved region driver helper > * @dev: Device from iommu_get_resv_regions() > @@ -846,6 +909,34 @@ static struct iommu_dma_msi_page *iommu_dma_get_msi_page(struct device *dev, > if (msi_page->phys == msi_addr) > return msi_page; > > + /* > + * In nested stage mode, we do not allocate an MSI page in > + * a range provided by the user. Instead, IOVA/IPA bindings are > + * individually provided. We reuse thise IOVAs to build the > + * IOVA -> IPA -> MSI PA nested stage mapping. > + */ > + if (cookie->type == IOMMU_DMA_NESTED_MSI_COOKIE) { > + list_for_each_entry(msi_page, &cookie->msi_page_list, list) > + if (!msi_page->phys) { /* this binding is free to use */ > + dma_addr_t ipa = msi_page->ipa; > + int ret; > + > + msi_page->phys = msi_addr; > + > + /* do the stage 2 mapping */ > + ret = iommu_map(domain, ipa, msi_addr, size, > + IOMMU_MMIO | IOMMU_WRITE); > + if (ret) { > + pr_warn("MSI S2 mapping failed (%d)\n", > + ret); > + return NULL; > + } > + return msi_page; > + } > + pr_warn("%s no MSI binding found\n", __func__); > + return NULL; > + } > + > msi_page = kzalloc(sizeof(*msi_page), GFP_ATOMIC); > if (!msi_page) > return NULL; > diff --git a/include/linux/dma-iommu.h b/include/linux/dma-iommu.h > index e8ca5e654277..324745eef644 100644 > --- a/include/linux/dma-iommu.h > +++ b/include/linux/dma-iommu.h > @@ -24,6 +24,7 @@ > #include <linux/dma-mapping.h> > #include <linux/iommu.h> > #include <linux/msi.h> > +#include <uapi/linux/iommu.h> > > int iommu_dma_init(void); > > @@ -74,12 +75,15 @@ int iommu_dma_mapping_error(struct device *dev, dma_addr_t dma_addr); > /* The DMA API isn't _quite_ the whole story, though... */ > void iommu_dma_map_msi_msg(int irq, struct msi_msg *msg); > void iommu_dma_get_resv_regions(struct device *dev, struct list_head *list); > +int iommu_dma_bind_doorbell(struct iommu_domain *domain, > + struct iommu_guest_msi_binding *binding); > > #else > > struct iommu_domain; > struct msi_msg; > struct device; > +struct iommu_guest_msi_binding; > > static inline int iommu_dma_init(void) > { > @@ -104,6 +108,13 @@ static inline void iommu_dma_map_msi_msg(int irq, struct msi_msg *msg) > { > } > > +static inline int > +iommu_dma_bind_doorbell(struct iommu_domain *domain, > + struct iommu_guest_msi_binding *binding) > +{ > + return -ENODEV; > +} > + > static inline void iommu_dma_get_resv_regions(struct device *dev, struct list_head *list) > { > } >
| |