[Xen-devel] [PATCH v5 05/10] domain: introduce XEN_DOMCTL_CDF_iommu flag

[Paul Durrant <paul.durrant@citrix.com>]

This patch introduces a common domain creation flag to determine whether
the domain is permitted to make use of the IOMMU. Currently the flag is
always set (for both dom0 and domU) if the IOMMU is globally enabled
(i.e. iommu_enabled == 1). sanitise_domain_config() is modified to reject
the flag if !iommu_enabled.

A new helper function, is_iommu_enabled(), is added to test the flag and
iommu_domain_init() will return immediately if !is_iommu_enabled(). This is
slightly different to the previous behaviour based on !iommu_enabled where
the call to arch_iommu_domain_init() was made regardless, however it appears
that this call was only necessary to initialize the dt_devices list for ARM
such that iommu_release_dt_devices() can be called unconditionally by
domain_relinquish_resources(). Adding a simple check of is_iommu_enabled()
into iommu_release_dt_devices() keeps this unconditional call working.

No functional change should be observed with this patch applied.

Subsequent patches will allow the toolstack to control whether use of the
IOMMU is enabled for a domain.

NOTE: The introduction of the is_iommu_enabled() helper function might
      seem excessive but its use is expected to increase with subsequent
      patches. Also, having iommu_domain_init() bail before calling
      arch_iommu_domain_init() is not strictly necessary, but I think the
      consequent addition of the call to is_iommu_enabled() in
      iommu_release_dt_devices() makes the code clearer.

Signed-off-by: Paul Durrant <paul.durrant@citrix.com>
---
Cc: Ian Jackson <ian.jackson@eu.citrix.com>
Cc: Wei Liu <wl@xen.org>
Cc: Anthony PERARD <anthony.perard@citrix.com>
Cc: Andrew Cooper <andrew.cooper3@citrix.com>
Cc: George Dunlap <George.Dunlap@eu.citrix.com>
Cc: Jan Beulich <jbeulich@suse.com>
Cc: Julien Grall <julien.grall@arm.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Stefano Stabellini <sstabellini@kernel.org>
Cc: Tim Deegan <tim@xen.org>
Cc: Volodymyr Babchuk <Volodymyr_Babchuk@epam.com>
Cc: "Roger Pau Monné" <roger.pau@citrix.com>

Previously part of series https://lists.xenproject.org/archives/html/xen-devel/2019-07/msg02267.html

v5:
 - Move is_iommu_enabled() check into iommu_domain_init()
 - Reject XEN_DOMCTL_CDF_iommu in sanitise_domain_config() if !iommu_enabled
 - Use evaluate_nospec() in defintion of is_iommu_enabled()
---
 tools/libxl/libxl_create.c            | 8 ++++++++
 xen/arch/arm/domain.c                 | 1 -
 xen/arch/arm/setup.c                  | 3 +++
 xen/arch/x86/setup.c                  | 3 +++
 xen/common/domain.c                   | 9 ++++++++-
 xen/drivers/passthrough/device_tree.c | 3 +++
 xen/drivers/passthrough/iommu.c       | 6 +++---
 xen/include/public/domctl.h           | 4 ++++
 xen/include/xen/sched.h               | 5 +++++
 9 files changed, 37 insertions(+), 5 deletions(-)

diff --git a/tools/libxl/libxl_create.c b/tools/libxl/libxl_create.c
index 03ce166f4f..050ef042cd 100644
--- a/tools/libxl/libxl_create.c
+++ b/tools/libxl/libxl_create.c
@@ -555,6 +555,7 @@ int libxl__domain_make(libxl__gc *gc, libxl_domain_config *d_config,
             .max_grant_frames = b_info->max_grant_frames,
             .max_maptrack_frames = b_info->max_maptrack_frames,
         };
+        libxl_physinfo physinfo;
 
         if (info->type != LIBXL_DOMAIN_TYPE_PV) {
             create.flags |= XEN_DOMCTL_CDF_hvm_guest;
@@ -564,6 +565,13 @@ int libxl__domain_make(libxl__gc *gc, libxl_domain_config *d_config,
                 libxl_defbool_val(info->oos) ? 0 : XEN_DOMCTL_CDF_oos_off;
         }
 
+        rc = libxl_get_physinfo(ctx, &physinfo);
+        if (rc < 0)
+            goto out;
+
+        if (physinfo.cap_hvm_directio)
+            create.flags |= XEN_DOMCTL_CDF_iommu;
+
         /* Ultimately, handle is an array of 16 uint8_t, same as uuid */
         libxl_uuid_copy(ctx, (libxl_uuid *)&create.handle, &info->uuid);
 
diff --git a/xen/arch/arm/domain.c b/xen/arch/arm/domain.c
index 941bbff4fe..3ff19bc1ca 100644
--- a/xen/arch/arm/domain.c
+++ b/xen/arch/arm/domain.c
@@ -673,7 +673,6 @@ int arch_domain_create(struct domain *d,
 
     ASSERT(config != NULL);
 
-    /* p2m_init relies on some value initialized by the IOMMU subsystem */
     if ( (rc = iommu_domain_init(d)) != 0 )
         goto fail;
 
diff --git a/xen/arch/arm/setup.c b/xen/arch/arm/setup.c
index 215746a5c3..fca1e62901 100644
--- a/xen/arch/arm/setup.c
+++ b/xen/arch/arm/setup.c
@@ -914,6 +914,9 @@ void __init start_xen(unsigned long boot_phys_offset,
     dom0_cfg.arch.tee_type = tee_get_type();
     dom0_cfg.max_vcpus = dom0_max_vcpus();
 
+    if ( iommu_enabled )
+        dom0_cfg.flags |= XEN_DOMCTL_CDF_iommu;
+
     dom0 = domain_create(0, &dom0_cfg, true);
     if ( IS_ERR(dom0) || (alloc_dom0_vcpu0(dom0) == NULL) )
         panic("Error creating domain 0\n");
diff --git a/xen/arch/x86/setup.c b/xen/arch/x86/setup.c
index d0b35b0ce2..fa226a2bab 100644
--- a/xen/arch/x86/setup.c
+++ b/xen/arch/x86/setup.c
@@ -1733,6 +1733,9 @@ void __init noreturn __start_xen(unsigned long mbi_p)
     }
     dom0_cfg.max_vcpus = dom0_max_vcpus();
 
+    if ( iommu_enabled )
+        dom0_cfg.flags |= XEN_DOMCTL_CDF_iommu;
+
     /* Create initial domain 0. */
     dom0 = domain_create(get_initial_domain_id(), &dom0_cfg, !pv_shim);
     if ( IS_ERR(dom0) || (alloc_dom0_vcpu0(dom0) == NULL) )
diff --git a/xen/common/domain.c b/xen/common/domain.c
index 76e6976617..e832a5c4aa 100644
--- a/xen/common/domain.c
+++ b/xen/common/domain.c
@@ -301,7 +301,8 @@ static int sanitise_domain_config(struct xen_domctl_createdomain *config)
                            XEN_DOMCTL_CDF_hap |
                            XEN_DOMCTL_CDF_s3_integrity |
                            XEN_DOMCTL_CDF_oos_off |
-                           XEN_DOMCTL_CDF_xs_domain) )
+                           XEN_DOMCTL_CDF_xs_domain |
+                           XEN_DOMCTL_CDF_iommu) )
     {
         dprintk(XENLOG_INFO, "Unknown CDF flags %#x\n", config->flags);
         return -EINVAL;
@@ -328,6 +329,12 @@ static int sanitise_domain_config(struct xen_domctl_createdomain *config)
         config->flags |= XEN_DOMCTL_CDF_oos_off;
     }
 
+    if ( (config->flags & XEN_DOMCTL_CDF_iommu) && !iommu_enabled )
+    {
+        dprintk(XENLOG_INFO, "IOMMU is not enabled\n");
+        return -EINVAL;
+    }
+
     return arch_sanitise_domain_config(config);
 }
 
diff --git a/xen/drivers/passthrough/device_tree.c b/xen/drivers/passthrough/device_tree.c
index b6eaae7283..d32b172664 100644
--- a/xen/drivers/passthrough/device_tree.c
+++ b/xen/drivers/passthrough/device_tree.c
@@ -119,6 +119,9 @@ int iommu_release_dt_devices(struct domain *d)
     struct dt_device_node *dev, *_dev;
     int rc;
 
+    if ( !is_iommu_enabled(d) )
+        return 0;
+
     list_for_each_entry_safe(dev, _dev, &hd->dt_devices, domain_list)
     {
         rc = iommu_deassign_dt_device(d, dev);
diff --git a/xen/drivers/passthrough/iommu.c b/xen/drivers/passthrough/iommu.c
index 37eb0f7d01..e61d3d1368 100644
--- a/xen/drivers/passthrough/iommu.c
+++ b/xen/drivers/passthrough/iommu.c
@@ -151,13 +151,13 @@ int iommu_domain_init(struct domain *d)
     struct domain_iommu *hd = dom_iommu(d);
     int ret = 0;
 
+    if ( !is_iommu_enabled(d) )
+        return 0;
+
     ret = arch_iommu_domain_init(d);
     if ( ret )
         return ret;
 
-    if ( !iommu_enabled )
-        return 0;
-
     hd->platform_ops = iommu_get_ops();
     return hd->platform_ops->init(d);
 }
diff --git a/xen/include/public/domctl.h b/xen/include/public/domctl.h
index 19486d5e32..3f82c78870 100644
--- a/xen/include/public/domctl.h
+++ b/xen/include/public/domctl.h
@@ -64,6 +64,10 @@ struct xen_domctl_createdomain {
  /* Is this a xenstore domain? */
 #define _XEN_DOMCTL_CDF_xs_domain     4
 #define XEN_DOMCTL_CDF_xs_domain      (1U<<_XEN_DOMCTL_CDF_xs_domain)
+ /* Should this domain be permitted to use the IOMMU? */
+#define _XEN_DOMCTL_CDF_iommu         5
+#define XEN_DOMCTL_CDF_iommu          (1U<<_XEN_DOMCTL_CDF_iommu)
+
     uint32_t flags;
 
     /*
diff --git a/xen/include/xen/sched.h b/xen/include/xen/sched.h
index a62161cc54..07ed66913a 100644
--- a/xen/include/xen/sched.h
+++ b/xen/include/xen/sched.h
@@ -981,6 +981,11 @@ static inline bool is_xenstore_domain(const struct domain *d)
     return d->options & XEN_DOMCTL_CDF_xs_domain;
 }
 
+static inline bool is_iommu_enabled(const struct domain *d)
+{
+    return evaluate_nospec(d->options & XEN_DOMCTL_CDF_iommu);
+}
+
 extern bool sched_smt_power_savings;
 
 extern enum cpufreq_controller {
-- 
2.20.1.2.gb21ebb671


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