xen/grant-dma-ops: Add option to restrict memory access under Xen
Introduce Xen grant DMA-mapping layer which contains special DMA-mapping routines for providing grant references as DMA addresses to be used by frontends (e.g. virtio) in Xen guests. Add the needed functionality by providing a special set of DMA ops handling the needed grant operations for the I/O pages. The subsequent commit will introduce the use case for xen-grant DMA ops layer to enable using virtio devices in Xen guests in a safe manner. Signed-off-by: Juergen Gross <jgross@suse.com> Signed-off-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com> Reviewed-by: Stefano Stabellini <sstabellini@kernel.org> Link: https://lore.kernel.org/r/1654197833-25362-4-git-send-email-olekstysh@gmail.com Signed-off-by: Juergen Gross <jgross@suse.com>
This commit is contained in:
Juergen Gross
parent
02a9e681a3
commit
d6aca3504c
@ -335,4 +335,8 @@ config XEN_UNPOPULATED_ALLOC
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having to balloon out RAM regions in order to obtain physical memory
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space to create such mappings.
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config XEN_GRANT_DMA_OPS
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bool
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select DMA_OPS
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endmenu
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@ -39,3 +39,4 @@ xen-gntalloc-y := gntalloc.o
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xen-privcmd-y := privcmd.o privcmd-buf.o
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obj-$(CONFIG_XEN_FRONT_PGDIR_SHBUF) += xen-front-pgdir-shbuf.o
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obj-$(CONFIG_XEN_UNPOPULATED_ALLOC) += unpopulated-alloc.o
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obj-$(CONFIG_XEN_GRANT_DMA_OPS) += grant-dma-ops.o
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312
drivers/xen/grant-dma-ops.c
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312
drivers/xen/grant-dma-ops.c
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@ -0,0 +1,312 @@
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// SPDX-License-Identifier: GPL-2.0-only
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/*
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* Xen grant DMA-mapping layer - contains special DMA-mapping routines
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* for providing grant references as DMA addresses to be used by frontends
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* (e.g. virtio) in Xen guests
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*
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* Copyright (c) 2021, Juergen Gross <jgross@suse.com>
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*/
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#include <linux/module.h>
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#include <linux/dma-map-ops.h>
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#include <linux/of.h>
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#include <linux/pfn.h>
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#include <linux/xarray.h>
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#include <xen/xen.h>
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#include <xen/xen-ops.h>
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#include <xen/grant_table.h>
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struct xen_grant_dma_data {
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/* The ID of backend domain */
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domid_t backend_domid;
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/* Is device behaving sane? */
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bool broken;
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};
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static DEFINE_XARRAY(xen_grant_dma_devices);
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#define XEN_GRANT_DMA_ADDR_OFF (1ULL << 63)
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static inline dma_addr_t grant_to_dma(grant_ref_t grant)
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{
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return XEN_GRANT_DMA_ADDR_OFF | ((dma_addr_t)grant << PAGE_SHIFT);
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}
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static inline grant_ref_t dma_to_grant(dma_addr_t dma)
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{
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return (grant_ref_t)((dma & ~XEN_GRANT_DMA_ADDR_OFF) >> PAGE_SHIFT);
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}
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static struct xen_grant_dma_data *find_xen_grant_dma_data(struct device *dev)
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{
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struct xen_grant_dma_data *data;
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xa_lock(&xen_grant_dma_devices);
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data = xa_load(&xen_grant_dma_devices, (unsigned long)dev);
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xa_unlock(&xen_grant_dma_devices);
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return data;
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}
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/*
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* DMA ops for Xen frontends (e.g. virtio).
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*
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* Used to act as a kind of software IOMMU for Xen guests by using grants as
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* DMA addresses.
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* Such a DMA address is formed by using the grant reference as a frame
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* number and setting the highest address bit (this bit is for the backend
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* to be able to distinguish it from e.g. a mmio address).
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*
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* Note that for now we hard wire dom0 to be the backend domain. In order
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* to support any domain as backend we'd need to add a way to communicate
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* the domid of this backend, e.g. via Xenstore, via the PCI-device's
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* config space or DT/ACPI.
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*/
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static void *xen_grant_dma_alloc(struct device *dev, size_t size,
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dma_addr_t *dma_handle, gfp_t gfp,
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unsigned long attrs)
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{
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struct xen_grant_dma_data *data;
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unsigned int i, n_pages = PFN_UP(size);
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unsigned long pfn;
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grant_ref_t grant;
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void *ret;
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data = find_xen_grant_dma_data(dev);
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if (!data)
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return NULL;
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if (unlikely(data->broken))
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return NULL;
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ret = alloc_pages_exact(n_pages * PAGE_SIZE, gfp);
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if (!ret)
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return NULL;
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pfn = virt_to_pfn(ret);
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if (gnttab_alloc_grant_reference_seq(n_pages, &grant)) {
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free_pages_exact(ret, n_pages * PAGE_SIZE);
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return NULL;
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}
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for (i = 0; i < n_pages; i++) {
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gnttab_grant_foreign_access_ref(grant + i, data->backend_domid,
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pfn_to_gfn(pfn + i), 0);
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}
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*dma_handle = grant_to_dma(grant);
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return ret;
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}
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static void xen_grant_dma_free(struct device *dev, size_t size, void *vaddr,
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dma_addr_t dma_handle, unsigned long attrs)
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{
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struct xen_grant_dma_data *data;
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unsigned int i, n_pages = PFN_UP(size);
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grant_ref_t grant;
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data = find_xen_grant_dma_data(dev);
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if (!data)
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return;
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if (unlikely(data->broken))
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return;
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grant = dma_to_grant(dma_handle);
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for (i = 0; i < n_pages; i++) {
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if (unlikely(!gnttab_end_foreign_access_ref(grant + i))) {
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dev_alert(dev, "Grant still in use by backend domain, disabled for further use\n");
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data->broken = true;
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return;
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}
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}
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gnttab_free_grant_reference_seq(grant, n_pages);
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free_pages_exact(vaddr, n_pages * PAGE_SIZE);
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}
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static struct page *xen_grant_dma_alloc_pages(struct device *dev, size_t size,
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dma_addr_t *dma_handle,
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enum dma_data_direction dir,
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gfp_t gfp)
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{
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void *vaddr;
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vaddr = xen_grant_dma_alloc(dev, size, dma_handle, gfp, 0);
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if (!vaddr)
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return NULL;
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return virt_to_page(vaddr);
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}
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static void xen_grant_dma_free_pages(struct device *dev, size_t size,
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struct page *vaddr, dma_addr_t dma_handle,
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enum dma_data_direction dir)
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{
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xen_grant_dma_free(dev, size, page_to_virt(vaddr), dma_handle, 0);
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}
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static dma_addr_t xen_grant_dma_map_page(struct device *dev, struct page *page,
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unsigned long offset, size_t size,
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enum dma_data_direction dir,
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unsigned long attrs)
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{
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struct xen_grant_dma_data *data;
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unsigned int i, n_pages = PFN_UP(size);
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grant_ref_t grant;
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dma_addr_t dma_handle;
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if (WARN_ON(dir == DMA_NONE))
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return DMA_MAPPING_ERROR;
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data = find_xen_grant_dma_data(dev);
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if (!data)
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return DMA_MAPPING_ERROR;
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if (unlikely(data->broken))
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return DMA_MAPPING_ERROR;
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if (gnttab_alloc_grant_reference_seq(n_pages, &grant))
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return DMA_MAPPING_ERROR;
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for (i = 0; i < n_pages; i++) {
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gnttab_grant_foreign_access_ref(grant + i, data->backend_domid,
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xen_page_to_gfn(page) + i, dir == DMA_TO_DEVICE);
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}
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dma_handle = grant_to_dma(grant) + offset;
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return dma_handle;
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}
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static void xen_grant_dma_unmap_page(struct device *dev, dma_addr_t dma_handle,
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size_t size, enum dma_data_direction dir,
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unsigned long attrs)
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{
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struct xen_grant_dma_data *data;
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unsigned int i, n_pages = PFN_UP(size);
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grant_ref_t grant;
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if (WARN_ON(dir == DMA_NONE))
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return;
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data = find_xen_grant_dma_data(dev);
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if (!data)
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return;
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if (unlikely(data->broken))
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return;
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grant = dma_to_grant(dma_handle);
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for (i = 0; i < n_pages; i++) {
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if (unlikely(!gnttab_end_foreign_access_ref(grant + i))) {
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dev_alert(dev, "Grant still in use by backend domain, disabled for further use\n");
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data->broken = true;
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return;
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}
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}
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gnttab_free_grant_reference_seq(grant, n_pages);
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}
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static void xen_grant_dma_unmap_sg(struct device *dev, struct scatterlist *sg,
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int nents, enum dma_data_direction dir,
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unsigned long attrs)
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{
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struct scatterlist *s;
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unsigned int i;
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if (WARN_ON(dir == DMA_NONE))
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return;
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for_each_sg(sg, s, nents, i)
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xen_grant_dma_unmap_page(dev, s->dma_address, sg_dma_len(s), dir,
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attrs);
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}
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static int xen_grant_dma_map_sg(struct device *dev, struct scatterlist *sg,
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int nents, enum dma_data_direction dir,
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unsigned long attrs)
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{
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struct scatterlist *s;
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unsigned int i;
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if (WARN_ON(dir == DMA_NONE))
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return -EINVAL;
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for_each_sg(sg, s, nents, i) {
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s->dma_address = xen_grant_dma_map_page(dev, sg_page(s), s->offset,
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s->length, dir, attrs);
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if (s->dma_address == DMA_MAPPING_ERROR)
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goto out;
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sg_dma_len(s) = s->length;
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}
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return nents;
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out:
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xen_grant_dma_unmap_sg(dev, sg, i, dir, attrs | DMA_ATTR_SKIP_CPU_SYNC);
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sg_dma_len(sg) = 0;
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return -EIO;
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}
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static int xen_grant_dma_supported(struct device *dev, u64 mask)
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{
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return mask == DMA_BIT_MASK(64);
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}
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static const struct dma_map_ops xen_grant_dma_ops = {
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.alloc = xen_grant_dma_alloc,
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.free = xen_grant_dma_free,
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.alloc_pages = xen_grant_dma_alloc_pages,
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.free_pages = xen_grant_dma_free_pages,
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.mmap = dma_common_mmap,
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.get_sgtable = dma_common_get_sgtable,
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.map_page = xen_grant_dma_map_page,
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.unmap_page = xen_grant_dma_unmap_page,
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.map_sg = xen_grant_dma_map_sg,
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.unmap_sg = xen_grant_dma_unmap_sg,
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.dma_supported = xen_grant_dma_supported,
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};
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void xen_grant_setup_dma_ops(struct device *dev)
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{
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struct xen_grant_dma_data *data;
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data = find_xen_grant_dma_data(dev);
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if (data) {
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dev_err(dev, "Xen grant DMA data is already created\n");
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return;
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}
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data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
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if (!data)
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goto err;
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/* XXX The dom0 is hardcoded as the backend domain for now */
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data->backend_domid = 0;
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if (xa_err(xa_store(&xen_grant_dma_devices, (unsigned long)dev, data,
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GFP_KERNEL))) {
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dev_err(dev, "Cannot store Xen grant DMA data\n");
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goto err;
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}
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dev->dma_ops = &xen_grant_dma_ops;
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return;
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err:
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dev_err(dev, "Cannot set up Xen grant DMA ops, retain platform DMA ops\n");
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}
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MODULE_DESCRIPTION("Xen grant DMA-mapping layer");
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MODULE_AUTHOR("Juergen Gross <jgross@suse.com>");
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MODULE_LICENSE("GPL");
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@ -214,4 +214,12 @@ static inline void xen_preemptible_hcall_end(void) { }
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#endif /* CONFIG_XEN_PV && !CONFIG_PREEMPTION */
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#ifdef CONFIG_XEN_GRANT_DMA_OPS
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void xen_grant_setup_dma_ops(struct device *dev);
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#else
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static inline void xen_grant_setup_dma_ops(struct device *dev)
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{
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}
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#endif /* CONFIG_XEN_GRANT_DMA_OPS */
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#endif /* INCLUDE_XEN_OPS_H */
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