xen-project/xen
1
0 Fork 0
mirror of https://github.com/xen-project/xen.git synced 2026-10-28 02:01:24 +01:00
Code Issues Activity

xen/gnttab: Reduce code volume when using union grant_combo

Browse Source 
There is no need for 'struct { ... } shorts' to be named.  Convert it to being
an anonymous struct, and rename 'word' to the more common 'raw'.

For _set_status_v1() and gnttab_prepare_for_transfer() which use a bounded
cmpxchg loop, rename {prev,new}_scombo to {prev,new} and reduce their scope to
within the loop.

For _set_status_v2(), the flags and id variables are completely unnecessary.
Drop them.

No functional change.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
This commit is contained in:
Andrew Cooper committed 2019-06-28 13:17:53 +01:00
1 parent 8dc0b31dc4
commit c097c46a73
1 file changed
+41 -50
Download Patch File Download Diff File Expand all files Collapse all files
xen/common/grant_table.c
+41 -50
View File
@@ -144,11 +144,11 @@ custom_param("gnttab", parse_gnttab);
* The following union allows that to happen in an endian-neutral fashion.
*/
union grant_combo {
uint32_t word;
uint32_t raw;
struct {
uint16_t flags;
domid_t domid;
} shorts;
};
};
/* Used to share code between unmap_grant_ref and unmap_and_replace. */
@@ -680,7 +680,7 @@ static int _set_status_v1(const grant_entry_header_t *shah,
{
int rc = GNTST_okay;
uint32_t *raw_shah = (uint32_t *)shah;
union grant_combo scombo, prev_scombo, new_scombo;
union grant_combo scombo;
uint16_t mask = GTF_type_mask;
/*
@@ -698,7 +698,7 @@ static int _set_status_v1(const grant_entry_header_t *shah,
if ( mapflag )
mask |= GTF_sub_page;
scombo.word = ACCESS_ONCE(*raw_shah);
scombo.raw = ACCESS_ONCE(*raw_shah);
/*
* This loop attempts to set the access (reading/writing) flags
@@ -708,37 +708,35 @@ static int _set_status_v1(const grant_entry_header_t *shah,
*/
for ( ; ; )
{
union grant_combo prev, new;
/* If not already pinned, check the grant domid and type. */
if ( !act->pin &&
(((scombo.shorts.flags & mask) !=
GTF_permit_access) ||
(scombo.shorts.domid != ldomid)) )
if ( !act->pin && (((scombo.flags & mask) != GTF_permit_access) ||
(scombo.domid != ldomid)) )
PIN_FAIL(done, GNTST_general_error,
"Bad flags (%x) or dom (%d); expected d%d\n",
scombo.shorts.flags, scombo.shorts.domid,
ldomid);
scombo.flags, scombo.domid, ldomid);
new_scombo = scombo;
new_scombo.shorts.flags |= GTF_reading;
new = scombo;
new.flags |= GTF_reading;
if ( !readonly )
{
new_scombo.shorts.flags |= GTF_writing;
if ( unlikely(scombo.shorts.flags & GTF_readonly) )
new.flags |= GTF_writing;
if ( unlikely(scombo.flags & GTF_readonly) )
PIN_FAIL(done, GNTST_general_error,
"Attempt to write-pin a r/o grant entry\n");
}
prev_scombo.word = guest_cmpxchg(rd, raw_shah,
scombo.word, new_scombo.word);
if ( likely(prev_scombo.word == scombo.word) )
prev.raw = guest_cmpxchg(rd, raw_shah, scombo.raw, new.raw);
if ( likely(prev.raw == scombo.raw) )
break;
if ( retries++ == 4 )
PIN_FAIL(done, GNTST_general_error,
"Shared grant entry is unstable\n");
scombo = prev_scombo;
scombo = prev;
}
done:
@@ -756,13 +754,9 @@ static int _set_status_v2(const grant_entry_header_t *shah,
int rc = GNTST_okay;
uint32_t *raw_shah = (uint32_t *)shah;
union grant_combo scombo;
uint16_t flags = shah->flags;
domid_t id = shah->domid;
uint16_t mask = GTF_type_mask;
scombo.word = ACCESS_ONCE(*raw_shah);
flags = scombo.shorts.flags;
id = scombo.shorts.domid;
scombo.raw = ACCESS_ONCE(*raw_shah);
/* if this is a grant mapping operation we should ensure GTF_sub_page
is not set */
@@ -770,13 +764,12 @@ static int _set_status_v2(const grant_entry_header_t *shah,
mask |= GTF_sub_page;
/* If not already pinned, check the grant domid and type. */
if ( !act->pin &&
( (((flags & mask) != GTF_permit_access) &&
((flags & mask) != GTF_transitive)) ||
(id != ldomid)) )
if ( !act->pin && ((((scombo.flags & mask) != GTF_permit_access) &&
((scombo.flags & mask) != GTF_transitive)) ||
(scombo.domid != ldomid)) )
PIN_FAIL(done, GNTST_general_error,
"Bad flags (%x) or dom (%d); expected d%d, flags %x\n",
flags, id, ldomid, mask);
scombo.flags, scombo.domid, ldomid, mask);
if ( readonly )
{
@@ -784,7 +777,7 @@ static int _set_status_v2(const grant_entry_header_t *shah,
}
else
{
if ( unlikely(flags & GTF_readonly) )
if ( unlikely(scombo.flags & GTF_readonly) )
PIN_FAIL(done, GNTST_general_error,
"Attempt to write-pin a r/o grant entry\n");
*status |= GTF_reading | GTF_writing;
@@ -794,27 +787,25 @@ static int _set_status_v2(const grant_entry_header_t *shah,
still valid */
smp_mb();
scombo.word = ACCESS_ONCE(*raw_shah);
flags = scombo.shorts.flags;
id = scombo.shorts.domid;
scombo.raw = ACCESS_ONCE(*raw_shah);
if ( !act->pin )
{
if ( (((flags & mask) != GTF_permit_access) &&
((flags & mask) != GTF_transitive)) ||
(id != ldomid) ||
(!readonly && (flags & GTF_readonly)) )
if ( (((scombo.flags & mask) != GTF_permit_access) &&
((scombo.flags & mask) != GTF_transitive)) ||
(scombo.domid != ldomid) ||
(!readonly && (scombo.flags & GTF_readonly)) )
{
gnttab_clear_flag(rd, _GTF_writing, status);
gnttab_clear_flag(rd, _GTF_reading, status);
PIN_FAIL(done, GNTST_general_error,
"Unstable flags (%x) or dom (%d); expected d%d (r/w: %d)\n",
flags, id, ldomid, !readonly);
scombo.flags, scombo.domid, ldomid, !readonly);
}
}
else
{
if ( unlikely(flags & GTF_readonly) )
if ( unlikely(scombo.flags & GTF_readonly) )
{
gnttab_clear_flag(rd, _GTF_writing, status);
PIN_FAIL(done, GNTST_general_error,
@@ -2038,7 +2029,7 @@ gnttab_prepare_for_transfer(
{
struct grant_table *rgt = rd->grant_table;
uint32_t *raw_shah;
union grant_combo scombo, prev_scombo, new_scombo;
union grant_combo scombo;
int retries = 0;
grant_read_lock(rgt);
@@ -2052,26 +2043,26 @@ gnttab_prepare_for_transfer(
}
raw_shah = (uint32_t *)shared_entry_header(rgt, ref);
scombo.word = ACCESS_ONCE(*raw_shah);
scombo.raw = ACCESS_ONCE(*raw_shah);
for ( ; ; )
{
if ( unlikely(scombo.shorts.flags != GTF_accept_transfer) ||
unlikely(scombo.shorts.domid != ld->domain_id) )
union grant_combo prev, new;
if ( unlikely(scombo.flags != GTF_accept_transfer) ||
unlikely(scombo.domid != ld->domain_id) )
{
gdprintk(XENLOG_INFO,
"Bad flags (%x) or dom (%d); expected d%d\n",
scombo.shorts.flags, scombo.shorts.domid,
ld->domain_id);
scombo.flags, scombo.domid, ld->domain_id);
goto fail;
}
new_scombo = scombo;
new_scombo.shorts.flags |= GTF_transfer_committed;
new = scombo;
new.flags |= GTF_transfer_committed;
prev_scombo.word = guest_cmpxchg(rd, raw_shah,
scombo.word, new_scombo.word);
if ( likely(prev_scombo.word == scombo.word) )
prev.raw = guest_cmpxchg(rd, raw_shah, scombo.raw, new.raw);
if ( likely(prev.raw == scombo.raw) )
break;
if ( retries++ == 4 )
@@ -2080,7 +2071,7 @@ gnttab_prepare_for_transfer(
goto fail;
}
scombo = prev_scombo;
scombo = prev;
}
grant_read_unlock(rgt);
Reference in new issue
xen-project/xen
Block a user
Blocking a user prevents them from interacting with repositories, such as opening or commenting on pull requests or issues. Learn more about blocking a user.

The note is not visible to the blocked user.