[Xen-devel] [RFC PATCH 04/24] ARM: GICv3 ITS: map ITS command buffer

[Andre Przywara <andre.przywara@xxxxxxx>]

Instead of directly manipulating the tables in memory, an ITS driver
sends commands via a ring buffer to the ITS h/w to create or alter the
LPI mappings.
Allocate memory for that buffer and tell the ITS about it to be able
to send ITS commands.

Signed-off-by: Andre Przywara <andre.przywara@xxxxxxx>
---
 xen/arch/arm/gic-its.c        | 25 +++++++++++++++++++++++++
 xen/include/asm-arm/gic-its.h |  1 +
 2 files changed, 26 insertions(+)

diff --git a/xen/arch/arm/gic-its.c b/xen/arch/arm/gic-its.c
index 40238a2..c8a7a7e 100644
--- a/xen/arch/arm/gic-its.c
+++ b/xen/arch/arm/gic-its.c
@@ -18,6 +18,7 @@
 
 #include <xen/config.h>
 #include <xen/lib.h>
+#include <xen/err.h>
 #include <xen/device_tree.h>
 #include <xen/libfdt/libfdt.h>
 #include <asm/p2m.h>
@@ -56,6 +57,26 @@ static uint64_t encode_phys_addr(paddr_t addr, int page_bits)
     return ret | (addr & GENMASK(51, 48)) >> (48 - 12);
 }
 
+static void *gicv3_map_cbaser(void __iomem *cbasereg)
+{
+    uint64_t attr, reg;
+    void *buffer;
+
+    attr  = GIC_BASER_InnerShareable << GITS_BASER_SHAREABILITY_SHIFT;
+    attr |= GIC_BASER_CACHE_SameAsInner << GITS_BASER_OUTER_CACHEABILITY_SHIFT;
+    attr |= GIC_BASER_CACHE_RaWaWb << GITS_BASER_INNER_CACHEABILITY_SHIFT;
+
+    buffer = alloc_xenheap_pages(0, 0);
+    if ( !buffer )
+        return ERR_PTR(-ENOMEM);
+
+    /* We use exactly one 4K page, so the "Size" field is 0. */
+    reg = attr | BIT(63) | (virt_to_maddr(buffer) & GENMASK(51, 12));
+    writeq_relaxed(reg, cbasereg);
+
+    return buffer;
+}
+
 static int gicv3_map_baser(void __iomem *basereg, uint64_t regc, int nr_items)
 {
     uint64_t attr;
@@ -149,6 +170,10 @@ int gicv3_its_init(struct host_its *hw_its)
         }
     }
 
+    hw_its->cmd_buf = gicv3_map_cbaser(hw_its->its_base + GITS_CBASER);
+    if ( IS_ERR(hw_its->cmd_buf) )
+        return PTR_ERR(hw_its->cmd_buf);
+
     return 0;
 }
 
diff --git a/xen/include/asm-arm/gic-its.h b/xen/include/asm-arm/gic-its.h
index 589b889..b2a003f 100644
--- a/xen/include/asm-arm/gic-its.h
+++ b/xen/include/asm-arm/gic-its.h
@@ -69,6 +69,7 @@ struct host_its {
     paddr_t addr;
     paddr_t size;
     void __iomem *its_base;
+    void *cmd_buf;
 };
 
 extern struct list_head host_its_list;
-- 
2.9.0


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