[Qemu-devel] [PATCH V3 1/2] hd-geometry.c: Integrate HDIO_GETGEO in guessing for target-s390x

[Einar Lueck]

This patch extends the function hd_geometry_guess. It introduces a
target specific hook. The default implementation for this target
specific hook is empty, has therefore no effect and the existing logic
works as before. For target-s390x, the behaviour is chosen as follows:
If no geo could be guessed via guess_disk_lchs, a new function called
guess_disk_pchs is called. The latter utilizes HDIO_GET_GEO ioctl to ask
the underlying disk for geometry.
If this is not successful (e.g. image files) geometry is derived
from the size of the disk (as before).
The new HDIO_GETGEO logic is required for two use cases:
a) Support for geometries of Direct Attached Storage Disks (DASD)
on s390x configured as backing of virtio block devices.
b) Support for FCP attached SCSI disks that do not yet have a
partition table. Without this patch, fdisk -l on the host would
return different results then fdisk -l in the guest.

Signed-off-by: Einar Lueck <address@hidden>
Signed-off-by: Jens Freimann <address@hidden>
Reviewed-by: Carsten Otte <address@hidden>
Signed-off-by: Christian Borntraeger <address@hidden>
---
 hw/Makefile.objs |  6 ++++-
 hw/hd-geometry.c | 70 +++++++++++++++++++++++++++++++++++++++++++++++++++++++-
 2 files changed, 74 insertions(+), 2 deletions(-)

diff --git a/hw/Makefile.objs b/hw/Makefile.objs
index 447e32a..7832d2c 100644
--- a/hw/Makefile.objs
+++ b/hw/Makefile.objs
@@ -178,7 +178,7 @@ common-obj-$(CONFIG_MAX111X) += max111x.o
 common-obj-$(CONFIG_DS1338) += ds1338.o
 common-obj-y += i2c.o smbus.o smbus_eeprom.o
 common-obj-y += eeprom93xx.o
-common-obj-y += scsi-disk.o cdrom.o hd-geometry.o block-common.o
+common-obj-y += scsi-disk.o cdrom.o block-common.o
 common-obj-y += scsi-generic.o scsi-bus.o
 common-obj-y += hid.o
 common-obj-$(CONFIG_SSI) += ssi.o
@@ -209,6 +209,10 @@ obj-$(CONFIG_VGA) += vga.o
 obj-$(CONFIG_SOFTMMU) += device-hotplug.o
 obj-$(CONFIG_XEN) += xen_domainbuild.o xen_machine_pv.o
 
+# geometry is target/architecture dependent and therefore needs to be built
+# for every target platform
+obj-y += hd-geometry.o
+
 # Inter-VM PCI shared memory & VFIO PCI device assignment
 ifeq ($(CONFIG_PCI), y)
 obj-$(CONFIG_KVM) += ivshmem.o
diff --git a/hw/hd-geometry.c b/hw/hd-geometry.c
index c305143..98253d7 100644
--- a/hw/hd-geometry.c
+++ b/hw/hd-geometry.c
@@ -33,6 +33,10 @@
 #include "block/block.h"
 #include "hw/block-common.h"
 #include "trace.h"
+#ifdef __linux__
+#include <linux/fs.h>
+#include <linux/hdreg.h>
+#endif
 
 struct partition {
         uint8_t boot_ind;           /* 0x80 - active */
@@ -47,6 +51,39 @@ struct partition {
         uint32_t nr_sects;          /* nr of sectors in partition */
 } QEMU_PACKED;
 
+static void guess_chs_for_size(BlockDriverState *bs,
+                uint32_t *pcyls, uint32_t *pheads, uint32_t *psecs);
+
+/* try to get geometry from disk via HDIO_GETGEO ioctl
+   Return 0 if OK, -1 if ioctl does not work (e.g. image file) */
+inline static int guess_disk_pchs(BlockDriverState *bs,
+                    uint32_t *pcylinders, uint32_t *pheads,
+                    uint32_t *psectors, int *ptranslation)
+{
+#ifdef __linux__
+    struct hd_geometry geo;
+
+    if (bdrv_ioctl(bs, HDIO_GETGEO, &geo)) {
+        return -1;
+    }
+
+    /* HDIO_GETGEO may return success even though geo contains zeros
+       (e.g. certain multipath setups) */
+    if (!geo.heads || !geo.sectors || !geo.cylinders) {
+        return -1;
+    }
+
+    *pheads = geo.heads;
+    *psectors = geo.sectors;
+    *pcylinders = geo.cylinders;
+    *ptranslation = BIOS_ATA_TRANSLATION_NONE;
+    return 0;
+#else
+    return -1;
+#endif
+}
+
+
 /* try to guess the disk logical geometry from the MSDOS partition table.
    Return 0 if OK, -1 if could not guess */
 static int guess_disk_lchs(BlockDriverState *bs,
@@ -116,13 +153,43 @@ static void guess_chs_for_size(BlockDriverState *bs,
     *psecs = 63;
 }
 
+/* target specific geometry guessing hooks:
+ * return 0 if guess available, != 0 in any other case */
+#ifdef TARGET_S390X
+static inline int target_geometry_guess(BlockDriverState *bs,
+                          uint32_t *pcyls, uint32_t *pheads,
+                          uint32_t *psecs, int *ptranslation)
+{
+    int cyls, heads, secs;
+    if (!guess_disk_lchs(bs, &cyls, &heads, &secs)) {
+        *pcyls = cyls;
+        *pheads = heads;
+        *psecs = secs;
+        *ptranslation = BIOS_ATA_TRANSLATION_NONE;
+        return 0;
+    } else {
+        return guess_disk_pchs(bs, pcyls, pheads, psecs, ptranslation);
+    }
+}
+#else
+static inline int target_geometry_guess(BlockDriverState *bs,
+                          uint32_t *pcyls, uint32_t *pheads,
+                          uint32_t *psecs, int *ptranslation)
+{
+    return -1;
+}
+#endif
+
 void hd_geometry_guess(BlockDriverState *bs,
                        uint32_t *pcyls, uint32_t *pheads, uint32_t *psecs,
                        int *ptrans)
 {
     int cylinders, heads, secs, translation;
 
-    if (guess_disk_lchs(bs, &cylinders, &heads, &secs) < 0) {
+    if (!target_geometry_guess(bs, pcyls, pheads, psecs, &translation)) {
+        /* a target specific guess has highest priority */
+        goto out;
+    } else if (guess_disk_lchs(bs, &cylinders, &heads, &secs) < 0) {
         /* no LCHS guess: use a standard physical disk geometry  */
         guess_chs_for_size(bs, pcyls, pheads, psecs);
         translation = hd_bios_chs_auto_trans(*pcyls, *pheads, *psecs);
@@ -143,6 +210,7 @@ void hd_geometry_guess(BlockDriverState *bs,
            the logical geometry */
         translation = BIOS_ATA_TRANSLATION_NONE;
     }
+out:
     if (ptrans) {
         *ptrans = translation;
     }
-- 
1.7.12.4