[Qemu-block] [QEMU] [PATCH v3 7/8] bootdevice: FW_CFG interface for LCHS values

[Sam Eiderman]

Using fw_cfg, supply logical CHS values directly from QEMU to the BIOS.

Non-standard logical geometries break under QEMU.

A virtual disk which contains an operating system which depends on
logical geometries (consistent values being reported from BIOS INT13
AH=08) will most likely break under QEMU/SeaBIOS if it has non-standard
logical geometries - for example 56 SPT (sectors per track).
No matter what QEMU will report - SeaBIOS, for large enough disks - will
use LBA translation, which will report 63 SPT instead.

In addition we cannot force SeaBIOS to rely on physical geometries at
all. A virtio-blk-pci virtual disk with 255 phyiscal heads cannot
report more than 16 physical heads when moved to an IDE controller,
since the ATA spec allows a maximum of 16 heads - this is an artifact of
virtualization.

By supplying the logical geometries directly we are able to support such
"exotic" disks.

We serialize this information in a similar way to the "bootorder"
interface.
The new fw_cfg entry is "bios-geometry".

Reviewed-by: Karl Heubaum <address@hidden>
Reviewed-by: Arbel Moshe <address@hidden>
Signed-off-by: Sam Eiderman <address@hidden>
---
 bootdevice.c            | 38 ++++++++++++++++++++++++++++++++++++++
 hw/nvram/fw_cfg.c       | 14 +++++++++++---
 include/sysemu/sysemu.h |  1 +
 3 files changed, 50 insertions(+), 3 deletions(-)

diff --git a/bootdevice.c b/bootdevice.c
index 2b12fb85a4..5cd88f7fbf 100644
--- a/bootdevice.c
+++ b/bootdevice.c
@@ -405,3 +405,41 @@ void del_boot_device_lchs(DeviceState *dev, const char 
*suffix)
         }
     }
 }
+
+typedef struct QEMU_PACKED FWLCHSEntrySerialized {
+    /* Little-endian. */
+    uint32_t lcyls;
+    uint32_t lheads;
+    uint32_t lsecs;
+} FWLCHSEntrySerialized;
+
+/* Serialized as: (device name\0 + lchs struct) x devices */
+char *get_boot_devices_lchs_list(size_t *size)
+{
+    FWLCHSEntry *i;
+    FWLCHSEntrySerialized s;
+    size_t total = 0;
+    char *list = NULL;
+
+    QTAILQ_FOREACH(i, &fw_lchs, link) {
+        char *bootpath;
+        size_t len;
+
+        bootpath = get_boot_device_path(i->dev, false, i->suffix);
+        s.lcyls = cpu_to_le32(i->lcyls);
+        s.lheads = cpu_to_le32(i->lheads);
+        s.lsecs = cpu_to_le32(i->lsecs);
+
+        len = strlen(bootpath) + 1;
+        list = g_realloc(list, total + len + sizeof(s));
+        memcpy(&list[total], bootpath, len);
+        memcpy(&list[total + len], &s, sizeof(s));
+        total += len + sizeof(s);
+
+        g_free(bootpath);
+    }
+
+    *size = total;
+
+    return list;
+}
diff --git a/hw/nvram/fw_cfg.c b/hw/nvram/fw_cfg.c
index 9f7b7789bc..c1230fe11c 100644
--- a/hw/nvram/fw_cfg.c
+++ b/hw/nvram/fw_cfg.c
@@ -916,13 +916,21 @@ void *fw_cfg_modify_file(FWCfgState *s, const char 
*filename,
 
 static void fw_cfg_machine_reset(void *opaque)
 {
+    MachineClass *mc = MACHINE_GET_CLASS(qdev_get_machine());
+    FWCfgState *s = opaque;
     void *ptr;
     size_t len;
-    FWCfgState *s = opaque;
-    char *bootindex = get_boot_devices_list(&len);
+    char *buf;
 
-    ptr = fw_cfg_modify_file(s, "bootorder", (uint8_t *)bootindex, len);
+    buf = get_boot_devices_list(&len);
+    ptr = fw_cfg_modify_file(s, "bootorder", (uint8_t *)buf, len);
     g_free(ptr);
+
+    if (!mc->legacy_fw_cfg_order) {
+        buf = get_boot_devices_lchs_list(&len);
+        ptr = fw_cfg_modify_file(s, "bios-geometry", (uint8_t *)buf, len);
+        g_free(ptr);
+    }
 }
 
 static void fw_cfg_machine_ready(struct Notifier *n, void *data)
diff --git a/include/sysemu/sysemu.h b/include/sysemu/sysemu.h
index 173dfbb539..1ca8799588 100644
--- a/include/sysemu/sysemu.h
+++ b/include/sysemu/sysemu.h
@@ -174,6 +174,7 @@ void validate_bootdevices(const char *devices, Error 
**errp);
 void add_boot_device_lchs(DeviceState *dev, const char *suffix,
                           uint32_t lcyls, uint32_t lheads, uint32_t lsecs);
 void del_boot_device_lchs(DeviceState *dev, const char *suffix);
+char *get_boot_devices_lchs_list(size_t *size);
 
 /* handler to set the boot_device order for a specific type of MachineClass */
 typedef void QEMUBootSetHandler(void *opaque, const char *boot_order,
-- 
2.13.3