diff options
Diffstat (limited to 'usr.sbin/bhyve/block_if.c')
| -rw-r--r-- | usr.sbin/bhyve/block_if.c | 49 |
1 files changed, 49 insertions, 0 deletions
diff --git a/usr.sbin/bhyve/block_if.c b/usr.sbin/bhyve/block_if.c index b29bc78..1ec0344 100644 --- a/usr.sbin/bhyve/block_if.c +++ b/usr.sbin/bhyve/block_if.c @@ -390,6 +390,55 @@ blockif_close(struct blockif_ctxt *bc) } /* + * Return virtual C/H/S values for a given block. Use the algorithm + * outlined in the VHD specification to calculate values. + */ +void +blockif_chs(struct blockif_ctxt *bc, uint16_t *c, uint8_t *h, uint8_t *s) +{ + off_t sectors; /* total sectors of the block dev */ + off_t hcyl; /* cylinders times heads */ + uint16_t secpt; /* sectors per track */ + uint8_t heads; + + assert(bc->bc_magic == BLOCKIF_SIG); + + sectors = bc->bc_size / bc->bc_sectsz; + + /* Clamp the size to the largest possible with CHS */ + if (sectors > 65535UL*16*255) + sectors = 65535UL*16*255; + + if (sectors >= 65536UL*16*63) { + secpt = 255; + heads = 16; + hcyl = sectors / secpt; + } else { + secpt = 17; + hcyl = sectors / secpt; + heads = (hcyl + 1023) / 1024; + + if (heads < 4) + heads = 4; + + if (hcyl >= (heads * 1024) || heads > 16) { + secpt = 31; + heads = 16; + hcyl = sectors / secpt; + } + if (hcyl >= (heads * 1024)) { + secpt = 63; + heads = 16; + hcyl = sectors / secpt; + } + } + + *c = hcyl / heads; + *h = heads; + *s = secpt; +} + +/* * Accessors */ off_t |
