[xen master] IOMMU: add common API for device reserved memory

[patchbot@xxxxxxx]

commit faccb3a08b454201fa4e4f1d2e08282f07627166
Author:     Marek Marczykowski-Górecki <marmarek@xxxxxxxxxxxxxxxxxxxxxx>
AuthorDate: Mon Sep 26 11:10:31 2022 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Mon Sep 26 11:10:31 2022 +0200

    IOMMU: add common API for device reserved memory
    
    Add API similar to rmrr= and ivmd= arguments, but in a common code. This
    will allow drivers to register reserved memory regardless of the IOMMU
    vendor.
    The direct reason for this API is xhci-dbc console driver (aka xue),
    that needs to use DMA. But future change may unify command line
    arguments for user-supplied reserved memory, and it may be useful for
    other drivers in the future too.
    
    This commit just introduces an API, subsequent patches will plug it in
    appropriate places. The reserved memory ranges needs to be saved
    locally, because at the point when they are collected, Xen doesn't know
    yet which IOMMU driver will be used.
    
    Signed-off-by: Marek Marczykowski-Górecki <marmarek@xxxxxxxxxxxxxxxxxxxxxx>
    Acked-by: Jan Beulich <jbeulich@xxxxxxxx>
---
 xen/drivers/passthrough/iommu.c | 46 +++++++++++++++++++++++++++++++++++++++++
 xen/include/xen/iommu.h         | 14 +++++++++++++
 2 files changed, 60 insertions(+)

diff --git a/xen/drivers/passthrough/iommu.c b/xen/drivers/passthrough/iommu.c
index 134cdb47e0..5e2a720d29 100644
--- a/xen/drivers/passthrough/iommu.c
+++ b/xen/drivers/passthrough/iommu.c
@@ -669,6 +669,52 @@ bool_t iommu_has_feature(struct domain *d, enum 
iommu_feature feature)
     return is_iommu_enabled(d) && test_bit(feature, dom_iommu(d)->features);
 }
 
+#define MAX_EXTRA_RESERVED_RANGES 20
+struct extra_reserved_range {
+    unsigned long start;
+    unsigned long nr;
+    pci_sbdf_t sbdf;
+};
+static unsigned int __initdata nr_extra_reserved_ranges;
+static struct extra_reserved_range __initdata
+    extra_reserved_ranges[MAX_EXTRA_RESERVED_RANGES];
+
+int __init iommu_add_extra_reserved_device_memory(unsigned long start,
+                                                  unsigned long nr,
+                                                  pci_sbdf_t sbdf)
+{
+    unsigned int idx;
+
+    if ( nr_extra_reserved_ranges >= MAX_EXTRA_RESERVED_RANGES )
+        return -ENOMEM;
+
+    idx = nr_extra_reserved_ranges++;
+    extra_reserved_ranges[idx].start = start;
+    extra_reserved_ranges[idx].nr = nr;
+    extra_reserved_ranges[idx].sbdf = sbdf;
+
+    return 0;
+}
+
+int __init iommu_get_extra_reserved_device_memory(iommu_grdm_t *func,
+                                                  void *ctxt)
+{
+    unsigned int idx;
+    int ret;
+
+    for ( idx = 0; idx < nr_extra_reserved_ranges; idx++ )
+    {
+        ret = func(extra_reserved_ranges[idx].start,
+                   extra_reserved_ranges[idx].nr,
+                   extra_reserved_ranges[idx].sbdf.sbdf,
+                   ctxt);
+        if ( ret < 0 )
+            return ret;
+    }
+
+    return 0;
+}
+
 /*
  * Local variables:
  * mode: C
diff --git a/xen/include/xen/iommu.h b/xen/include/xen/iommu.h
index 1240d7762d..4f22fc1bed 100644
--- a/xen/include/xen/iommu.h
+++ b/xen/include/xen/iommu.h
@@ -304,6 +304,20 @@ struct iommu_ops {
 #endif
 };
 
+/*
+ * To be called by Xen internally, to register extra RMRR/IVMD ranges.
+ * Needs to be called before IOMMU initialization.
+ */
+extern int iommu_add_extra_reserved_device_memory(unsigned long start,
+                                                  unsigned long nr,
+                                                  pci_sbdf_t sbdf);
+/*
+ * To be called by specific IOMMU driver during initialization,
+ * to fetch ranges registered with iommu_add_extra_reserved_device_memory().
+ */
+extern int iommu_get_extra_reserved_device_memory(iommu_grdm_t *func,
+                                                  void *ctxt);
+
 #include <asm/iommu.h>
 
 #ifndef iommu_call
--
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