[Qemu-devel] [PATCH 2/2] hd-geometry.c: Integrate HDIO_GETGEO in guessing

[Jens Freimann <jfrei@linux.vnet.ibm.com>]

From: Einar Lueck <elelueck@linux.vnet.ibm.com>

This patch extends the function guess_disk_lchs. If no geo could
be derived from reading disk content, HDIO_GETGEO ioctl is issued.
If this is not successful (e.g. image files) geometry is derived
from the size of the disk (as before). To achieve this, the MSDOS
partition table reading logic and the translation computation logic
have been moved into a separate function guess_disk_msdosgeo. The
HDIO_GETGEO logic is captured in a new function guess_disk_ioctlgeo.
guess_disk_lchs then encapsulates both (the overall guessing logic).
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 <elelueck@linux.vnet.ibm.com>
Signed-off-by: Jens Freimann <jfrei@linux.vnet.ibm.com>

---
 hw/hd-geometry.c | 118 ++++++++++++++++++++++++++++++++++++++-----------------
 1 file changed, 81 insertions(+), 37 deletions(-)

diff --git a/hw/hd-geometry.c b/hw/hd-geometry.c
index 1cdb9fb..fc29075 100644
--- a/hw/hd-geometry.c
+++ b/hw/hd-geometry.c
@@ -33,6 +33,10 @@
 #include "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 */
@@ -47,13 +51,59 @@ 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)
+{
+    uint64_t nb_sectors;
+    int cylinders;
+
+    bdrv_get_geometry(bs, &nb_sectors);
+
+    cylinders = nb_sectors / (16 * 63);
+    if (cylinders > 16383) {
+        cylinders = 16383;
+    } else if (cylinders < 2) {
+        cylinders = 2;
+    }
+    *pcyls = cylinders;
+    *pheads = 16;
+    *psecs = 63;
+}
+
+/* try to get geometry from disk via HDIO_GETGEO ioctl
+   Return 0 if OK, -1 if ioctl does not work (e.g. image file) */
+static inline int guess_disk_ioctlgeo(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;
+    }
+
+    *pheads = geo.heads;
+    *psectors = geo.sectors;
+    *pcylinders = geo.cylinders;
+    *ptranslation = BIOS_ATA_TRANSLATION_NONE;
+    trace_hd_geometry_lchs_guess(bs, *pcylinders, *pheads, *psectors);
+    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,
-                           int *pcylinders, int *pheads, int *psectors)
+static int guess_disk_msdosgeo(BlockDriverState *bs,
+                               uint32_t *pcylinders, uint32_t *pheads,
+                               uint32_t *psectors, int *ptranslation)
 {
     uint8_t buf[BDRV_SECTOR_SIZE];
-    int i, heads, sectors, cylinders;
+    int i, translation;
+    uint32_t heads, sectors, cylinders;
     struct partition *p;
     uint32_t nr_sects;
     uint64_t nb_sectors;
@@ -87,9 +137,26 @@ static int guess_disk_lchs(BlockDriverState *bs,
             if (cylinders < 1 || cylinders > 16383) {
                 continue;
             }
+
+            if (heads > 16) {
+                /* LCHS guess with heads > 16 means that a BIOS LBA
+                   translation was active, so a standard physical disk
+                   geometry is OK */
+                guess_chs_for_size(bs, &cylinders, &heads, &sectors);
+                translation = cylinders * heads <= 131072
+                    ? BIOS_ATA_TRANSLATION_LARGE
+                    : BIOS_ATA_TRANSLATION_LBA;
+            } else {
+                /* LCHS guess with heads <= 16: use as physical geometry */
+                /* disable any translation to be in sync with
+                   the logical geometry */
+                translation = BIOS_ATA_TRANSLATION_NONE;
+            }
             *pheads = heads;
             *psectors = sectors;
             *pcylinders = cylinders;
+            *ptranslation = translation;
+
             trace_hd_geometry_lchs_guess(bs, cylinders, heads, sectors);
             return 0;
         }
@@ -97,51 +164,28 @@ static int guess_disk_lchs(BlockDriverState *bs,
     return -1;
 }
 
-static void guess_chs_for_size(BlockDriverState *bs,
-                uint32_t *pcyls, uint32_t *pheads, uint32_t *psecs)
-{
-    uint64_t nb_sectors;
-    int cylinders;
-
-    bdrv_get_geometry(bs, &nb_sectors);
-
-    cylinders = nb_sectors / (16 * 63);
-    if (cylinders > 16383) {
-        cylinders = 16383;
-    } else if (cylinders < 2) {
-        cylinders = 2;
+/* try to guess the disk logical geometry
+   Return 0 if OK, -1 if could not guess */
+static int guess_disk_lchs(BlockDriverState *bs,
+                           uint32_t *pcylinders, uint32_t *pheads,
+                           uint32_t *psectors, int *ptranslation) {
+    if (!guess_disk_msdosgeo(bs, pcylinders, pheads, psectors, ptranslation)) {
+        return 0;
     }
-    *pcyls = cylinders;
-    *pheads = 16;
-    *psecs = 63;
+
+    return guess_disk_ioctlgeo(bs, pcylinders, pheads, psectors, ptranslation);
 }
 
 void hd_geometry_guess(BlockDriverState *bs,
                        uint32_t *pcyls, uint32_t *pheads, uint32_t *psecs,
                        int *ptrans)
 {
-    int cylinders, heads, secs, translation;
+    int translation;
 
-    if (guess_disk_lchs(bs, &cylinders, &heads, &secs) < 0) {
+    if (guess_disk_lchs(bs, pcyls, pheads, psecs, &translation) < 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);
-    } else if (heads > 16) {
-        /* LCHS guess with heads > 16 means that a BIOS LBA
-           translation was active, so a standard physical disk
-           geometry is OK */
-        guess_chs_for_size(bs, pcyls, pheads, psecs);
-        translation = *pcyls * *pheads <= 131072
-            ? BIOS_ATA_TRANSLATION_LARGE
-            : BIOS_ATA_TRANSLATION_LBA;
-    } else {
-        /* LCHS guess with heads <= 16: use as physical geometry */
-        *pcyls = cylinders;
-        *pheads = heads;
-        *psecs = secs;
-        /* disable any translation to be in sync with
-           the logical geometry */
-        translation = BIOS_ATA_TRANSLATION_NONE;
     }
     if (ptrans) {
         *ptrans = translation;
-- 
1.7.11.4