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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] [PATCH 2/5] xen/gnttab: Reduce code volume when using union grant_combo
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@xxxxxxxxxx>
---
CC: Jan Beulich <JBeulich@xxxxxxxx>
CC: Wei Liu <wl@xxxxxxx>
CC: Roger Pau Monné <roger.pau@xxxxxxxxxx>
CC: Stefano Stabellini <sstabellini@xxxxxxxxxx>
CC: Julien Grall <julien.grall@xxxxxxx>
CC: George Dunlap <george.dunlap@xxxxxxxxxxxxx>
---
xen/common/grant_table.c | 91 ++++++++++++++++++++++--------------------------
1 file changed, 41 insertions(+), 50 deletions(-)
diff --git a/xen/common/grant_table.c b/xen/common/grant_table.c
index e5d585f..6d8f17d 100644
--- a/xen/common/grant_table.c
+++ b/xen/common/grant_table.c
@@ -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);
--
2.1.4
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