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Add a call to synthesize a C/H/S value for block emulations

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that require it (ahci). The algorithm used is from the VHD
specification.
This commit is contained in:
Peter Grehan 2014-07-15 00:25:54 +00:00
parent d634b1f709
commit c4813fadf1
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=268638
2 changed files with 51 additions and 0 deletions
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49
usr.sbin/bhyve/block_if.c
View File

@ -389,6 +389,55 @@ blockif_close(struct blockif_ctxt *bc)
return (0);
}
/*
* 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
*/

2
usr.sbin/bhyve/block_if.h
View File

@ -52,6 +52,8 @@ struct blockif_req {
struct blockif_ctxt;
struct blockif_ctxt *blockif_open(const char *optstr, const char *ident);
off_t blockif_size(struct blockif_ctxt *bc);
void blockif_chs(struct blockif_ctxt *bc, uint16_t *c, uint8_t *h,
uint8_t *s);
int blockif_sectsz(struct blockif_ctxt *bc);
int blockif_queuesz(struct blockif_ctxt *bc);
int blockif_is_ro(struct blockif_ctxt *bc);