[xen master] VT-d: install sync_cache hook on demand

[patchbot@xxxxxxx]

commit bf2a0ed11d4cf79e9863576f97a8d306fc3b1d40
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Fri Jul 17 17:48:42 2020 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Fri Jul 17 17:48:42 2020 +0200

    VT-d: install sync_cache hook on demand
    
    Instead of checking inside the hook whether any non-coherent IOMMUs are
    present, simply install the hook only when this is the case.
    
    To prove that there are no other references to the now dynamically
    updated ops structure (and hence that its updating happens early
    enough), make it static and rename it at the same time.
    
    Note that this change implies that sync_cache() shouldn't be called
    directly unless there are unusual circumstances, like is the case in
    alloc_pgtable_maddr(), which gets invoked too early for iommu_ops to
    be set already (and therefore we also need to be careful there to
    avoid accessing vtd_ops later on, as it lives in .init).
    
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    Reviewed-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
    Reviewed-by: Kevin Tian <kevin.tian@xxxxxxxxx>
---
 xen/drivers/passthrough/vtd/extern.h |  1 -
 xen/drivers/passthrough/vtd/iommu.c  | 16 ++++++----------
 2 files changed, 6 insertions(+), 11 deletions(-)

diff --git a/xen/drivers/passthrough/vtd/extern.h 
b/xen/drivers/passthrough/vtd/extern.h
index f776feefe6..ada3c3098c 100644
--- a/xen/drivers/passthrough/vtd/extern.h
+++ b/xen/drivers/passthrough/vtd/extern.h
@@ -28,7 +28,6 @@
 struct pci_ats_dev;
 extern bool_t rwbf_quirk;
 extern const struct iommu_init_ops intel_iommu_init_ops;
-extern const struct iommu_ops intel_iommu_ops;
 
 void print_iommu_regs(struct acpi_drhd_unit *drhd);
 void print_vtd_entries(struct vtd_iommu *iommu, int bus, int devfn, u64 gmfn);
diff --git a/xen/drivers/passthrough/vtd/iommu.c 
b/xen/drivers/passthrough/vtd/iommu.c
index 2a99cd208f..ef2fea0a0e 100644
--- a/xen/drivers/passthrough/vtd/iommu.c
+++ b/xen/drivers/passthrough/vtd/iommu.c
@@ -59,6 +59,7 @@ bool __read_mostly iommu_snoop = true;
 
 int nr_iommus;
 
+static struct iommu_ops vtd_ops;
 static struct tasklet vtd_fault_tasklet;
 
 static int setup_hwdom_device(u8 devfn, struct pci_dev *);
@@ -146,16 +147,11 @@ static int context_get_domain_id(struct context_entry 
*context,
     return domid;
 }
 
-static int iommus_incoherent;
-
 static void sync_cache(const void *addr, unsigned int size)
 {
     static unsigned long clflush_size = 0;
     const void *end = addr + size;
 
-    if ( !iommus_incoherent )
-        return;
-
     if ( clflush_size == 0 )
         clflush_size = get_cache_line_size();
 
@@ -217,7 +213,8 @@ uint64_t alloc_pgtable_maddr(unsigned long npages, nodeid_t 
node)
         vaddr = __map_domain_page(cur_pg);
         memset(vaddr, 0, PAGE_SIZE);
 
-        sync_cache(vaddr, PAGE_SIZE);
+        if ( (iommu_ops.init ? &iommu_ops : &vtd_ops)->sync_cache )
+            sync_cache(vaddr, PAGE_SIZE);
         unmap_domain_page(vaddr);
         cur_pg++;
     }
@@ -1227,7 +1224,7 @@ int __init iommu_alloc(struct acpi_drhd_unit *drhd)
     iommu->nr_pt_levels = agaw_to_level(agaw);
 
     if ( !ecap_coherent(iommu->ecap) )
-        iommus_incoherent = 1;
+        vtd_ops.sync_cache = sync_cache;
 
     /* allocate domain id bitmap */
     nr_dom = cap_ndoms(iommu->cap);
@@ -2737,7 +2734,7 @@ static int __init intel_iommu_quarantine_init(struct 
domain *d)
     return level ? -ENOMEM : rc;
 }
 
-const struct iommu_ops __initconstrel intel_iommu_ops = {
+static struct iommu_ops __initdata vtd_ops = {
     .init = intel_iommu_domain_init,
     .hwdom_init = intel_iommu_hwdom_init,
     .quarantine_init = intel_iommu_quarantine_init,
@@ -2768,11 +2765,10 @@ const struct iommu_ops __initconstrel intel_iommu_ops = 
{
     .iotlb_flush_all = iommu_flush_iotlb_all,
     .get_reserved_device_memory = intel_iommu_get_reserved_device_memory,
     .dump_p2m_table = vtd_dump_p2m_table,
-    .sync_cache = sync_cache,
 };
 
 const struct iommu_init_ops __initconstrel intel_iommu_init_ops = {
-    .ops = &intel_iommu_ops,
+    .ops = &vtd_ops,
     .setup = vtd_setup,
     .supports_x2apic = intel_iommu_supports_eim,
 };
--
generated by git-patchbot for /home/xen/git/xen.git#master