[Xen-devel] [PATCHv2] x86/xen: populate boot_params with EDD data

[David Vrabel <david.vrabel@xxxxxxxxxx>]

From: David Vrabel <david.vrabel@xxxxxxxxxx>

During early setup of a dom0 kernel, populate boot_params with the
Enhanced Disk Drive (EDD) and MBR signature data.  This makes
information on the BIOS boot device available in /sys/firmware/edd/.

Signed-off-by: David Vrabel <david.vrabel@xxxxxxxxxx>
---
v2:
- use IS_ENABLED()
- #if in the function looks more readable
---
 arch/x86/xen/enlighten.c |   52 ++++++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 52 insertions(+), 0 deletions(-)

diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index c8e1c7b..dfe5422 100644
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -31,6 +31,7 @@
 #include <linux/pci.h>
 #include <linux/gfp.h>
 #include <linux/memblock.h>
+#include <linux/edd.h>
 
 #include <xen/xen.h>
 #include <xen/events.h>
@@ -1306,6 +1307,55 @@ static const struct machine_ops xen_machine_ops 
__initconst = {
        .emergency_restart = xen_emergency_restart,
 };
 
+static void __init load_edd(void)
+{
+#if IS_ENABLED(CONFIG_EDD)
+       struct xen_platform_op op;
+       struct edd_info *edd_info;
+       u32 *mbr_signature;
+       unsigned nr;
+       int ret;
+
+       edd_info = boot_params.eddbuf;
+       mbr_signature = boot_params.edd_mbr_sig_buffer;
+
+       op.cmd = XENPF_firmware_info;
+
+       op.u.firmware_info.type = XEN_FW_DISK_INFO;
+       for (nr = 0; nr < EDDMAXNR; nr++) {
+               struct edd_info *info = edd_info + nr;
+
+               op.u.firmware_info.index = nr;
+               info->params.length = sizeof(info->params);
+               set_xen_guest_handle(op.u.firmware_info.u.disk_info.edd_params,
+                                    &info->params);
+               ret = HYPERVISOR_dom0_op(&op);
+               if (ret)
+                       break;
+
+#define C(x) info->x = op.u.firmware_info.u.disk_info.x
+               C(device);
+               C(version);
+               C(interface_support);
+               C(legacy_max_cylinder);
+               C(legacy_max_head);
+               C(legacy_sectors_per_track);
+#undef C
+       }
+       boot_params.eddbuf_entries = nr;
+
+       op.u.firmware_info.type = XEN_FW_DISK_MBR_SIGNATURE;
+       for (nr = 0; nr < EDD_MBR_SIG_MAX; nr++) {
+               op.u.firmware_info.index = nr;
+               ret = HYPERVISOR_dom0_op(&op);
+               if (ret)
+                       break;
+               mbr_signature[nr] = 
op.u.firmware_info.u.disk_mbr_signature.mbr_signature;
+       }
+       boot_params.edd_mbr_sig_buf_entries = nr;
+#endif
+}
+
 /*
  * Set up the GDT and segment registers for -fstack-protector.  Until
  * we do this, we have to be careful not to call any stack-protected
@@ -1508,6 +1558,8 @@ asmlinkage void __init xen_start_kernel(void)
                /* Avoid searching for BIOS MP tables */
                x86_init.mpparse.find_smp_config = x86_init_noop;
                x86_init.mpparse.get_smp_config = x86_init_uint_noop;
+
+               load_edd();
        }
 #ifdef CONFIG_PCI
        /* PCI BIOS service won't work from a PV guest. */
-- 
1.7.2.5


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