[RFC XEN PATCH v2 06/15] tools: reserve guest memory for ACPI from device model

[Haozhong Zhang <haozhong.zhang@intel.com>]

Some virtual devices (e.g. NVDIMM) require complex ACPI tables and
definition blocks (in AML), which a device model (e.g. QEMU) has
already been able to construct. Instead of introducing the similar
implementation to Xen, we would like to reuse the device model to
provide those ACPI stuffs.

This commit reserves an area in the guest memory for the device model
to pass its ACPI tables and definition blocks to guest, which will be
loaded by hvmloader. The base guest physical address and the size of
the reserved area are passed to the device model via XenStore keys
hvmloader/dm-acpi/{address, length}.

Signed-off-by: Haozhong Zhang <haozhong.zhang@intel.com>
---
Cc: Ian Jackson <ian.jackson@eu.citrix.com>
Cc: Wei Liu <wei.liu2@citrix.com>
---
 tools/libxc/include/xc_dom.h            |  1 +
 tools/libxc/xc_dom_x86.c                |  7 +++++++
 tools/libxl/libxl_dom.c                 | 22 ++++++++++++++++++++++
 xen/include/public/hvm/hvm_xs_strings.h | 11 +++++++++++
 4 files changed, 41 insertions(+)

diff --git a/tools/libxc/include/xc_dom.h b/tools/libxc/include/xc_dom.h
index 608cbc2ad6..19d65cda1e 100644
--- a/tools/libxc/include/xc_dom.h
+++ b/tools/libxc/include/xc_dom.h
@@ -98,6 +98,7 @@ struct xc_dom_image {
     xen_pfn_t xenstore_pfn;
     xen_pfn_t shared_info_pfn;
     xen_pfn_t bootstack_pfn;
+    xen_pfn_t dm_acpi_pfn;
     xen_pfn_t pfn_alloc_end;
     xen_vaddr_t virt_alloc_end;
     xen_vaddr_t bsd_symtab_start;
diff --git a/tools/libxc/xc_dom_x86.c b/tools/libxc/xc_dom_x86.c
index 6495e7fc30..917fb51abf 100644
--- a/tools/libxc/xc_dom_x86.c
+++ b/tools/libxc/xc_dom_x86.c
@@ -674,6 +674,13 @@ static int alloc_magic_pages_hvm(struct xc_dom_image *dom)
                          ioreq_server_pfn(0));
         xc_hvm_param_set(xch, domid, HVM_PARAM_NR_IOREQ_SERVER_PAGES,
                          NR_IOREQ_SERVER_PAGES);
+
+        dom->dm_acpi_pfn = xc_dom_alloc_page(dom, "DM ACPI");
+        if ( dom->dm_acpi_pfn == INVALID_PFN )
+        {
+            DOMPRINTF("Could not allocate page for device model ACPI.");
+            goto error_out;
+        }
     }
 
     rc = xc_dom_alloc_segment(dom, &dom->start_info_seg,
diff --git a/tools/libxl/libxl_dom.c b/tools/libxl/libxl_dom.c
index d519c8d440..5f621466d5 100644
--- a/tools/libxl/libxl_dom.c
+++ b/tools/libxl/libxl_dom.c
@@ -865,6 +865,28 @@ static int hvm_build_set_xs_values(libxl__gc *gc,
             goto err;
     }
 
+    if (dom->dm_acpi_pfn) {
+        uint64_t guest_addr_out = dom->dm_acpi_pfn * XC_DOM_PAGE_SIZE(dom);
+
+        if (guest_addr_out >= 0x100000000ULL) {
+            LOG(ERROR,
+                "Guest address of DM ACPI is 0x%"PRIx64", but expected below 4G",
+                guest_addr_out);
+            goto err;
+        }
+
+        path = GCSPRINTF("/local/domain/%d/"HVM_XS_DM_ACPI_ADDRESS, domid);
+        ret = libxl__xs_printf(gc, XBT_NULL, path, "0x%"PRIx64, guest_addr_out);
+        if (ret)
+            goto err;
+
+        path = GCSPRINTF("/local/domain/%d/"HVM_XS_DM_ACPI_LENGTH, domid);
+        ret = libxl__xs_printf(gc, XBT_NULL, path, "0x%"PRIx64,
+                               (uint64_t)XC_DOM_PAGE_SIZE(dom));
+        if (ret)
+            goto err;
+    }
+
     return 0;
 
 err:
diff --git a/xen/include/public/hvm/hvm_xs_strings.h b/xen/include/public/hvm/hvm_xs_strings.h
index 146b0b0582..f9b82dbbc0 100644
--- a/xen/include/public/hvm/hvm_xs_strings.h
+++ b/xen/include/public/hvm/hvm_xs_strings.h
@@ -79,4 +79,15 @@
  */
 #define HVM_XS_OEM_STRINGS             "bios-strings/oem-%d"
 
+/* Follows are XenStore keys for DM ACPI (ACPI built by device model,
+ * e.g. QEMU).
+ *
+ * A reserved area of guest physical memory is used to pass DM
+ * ACPI. Values of following two keys specify the base physical
+ * address and length (in bytes) of the reserved area.
+ */
+#define HVM_XS_DM_ACPI_ROOT            "hvmloader/dm-acpi"
+#define HVM_XS_DM_ACPI_ADDRESS         HVM_XS_DM_ACPI_ROOT"/address"
+#define HVM_XS_DM_ACPI_LENGTH          HVM_XS_DM_ACPI_ROOT"/length"
+
 #endif /* __XEN_PUBLIC_HVM_HVM_XS_STRINGS_H__ */
-- 
2.12.0


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