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authorMarc Zyngier <marc.zyngier@arm.com>2016-01-21 21:27:04 +0300
committerMarc Zyngier <marc.zyngier@arm.com>2016-02-29 21:34:22 +0300
commit623eefa8d04c6c3df69a0630989f10b3762b3b00 (patch)
treeca9bfd8f2c0308ef434df7674194eff0f578b6e0 /arch/arm64
parentbb0c70bcca6ba3c84afc2da7426f3b923bbe6825 (diff)
downloadlinux-623eefa8d04c6c3df69a0630989f10b3762b3b00.tar.xz
arm64: KVM: Switch the sys_reg search to be a binary search
Our 64bit sys_reg table is about 90 entries long (so far, and the PMU support is likely to increase this). This means that on average, it takes 45 comparaisons to find the right entry (and actually the full 90 if we have to search the invariant table). Not the most efficient thing. Specially when you think that this table is already sorted. Switching to a binary search effectively reduces the search to about 7 comparaisons. Slightly better! As an added bonus, the comparison is done by comparing all the fields at once, instead of one at a time. Reviewed-by: Christoffer Dall <christoffer.dall@linaro.org> Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Diffstat (limited to 'arch/arm64')
-rw-r--r--arch/arm64/kvm/sys_regs.c40
1 files changed, 22 insertions, 18 deletions
diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index fe15c2310a65..61ba59104845 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -20,6 +20,7 @@
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
+#include <linux/bsearch.h>
#include <linux/kvm_host.h>
#include <linux/mm.h>
#include <linux/uaccess.h>
@@ -1453,29 +1454,32 @@ static const struct sys_reg_desc *get_target_table(unsigned target,
}
}
+#define reg_to_match_value(x) \
+ ({ \
+ unsigned long val; \
+ val = (x)->Op0 << 14; \
+ val |= (x)->Op1 << 11; \
+ val |= (x)->CRn << 7; \
+ val |= (x)->CRm << 3; \
+ val |= (x)->Op2; \
+ val; \
+ })
+
+static int match_sys_reg(const void *key, const void *elt)
+{
+ const unsigned long pval = (unsigned long)key;
+ const struct sys_reg_desc *r = elt;
+
+ return pval - reg_to_match_value(r);
+}
+
static const struct sys_reg_desc *find_reg(const struct sys_reg_params *params,
const struct sys_reg_desc table[],
unsigned int num)
{
- unsigned int i;
-
- for (i = 0; i < num; i++) {
- const struct sys_reg_desc *r = &table[i];
+ unsigned long pval = reg_to_match_value(params);
- if (params->Op0 != r->Op0)
- continue;
- if (params->Op1 != r->Op1)
- continue;
- if (params->CRn != r->CRn)
- continue;
- if (params->CRm != r->CRm)
- continue;
- if (params->Op2 != r->Op2)
- continue;
-
- return r;
- }
- return NULL;
+ return bsearch((void *)pval, table, num, sizeof(table[0]), match_sys_reg);
}
int kvm_handle_cp14_load_store(struct kvm_vcpu *vcpu, struct kvm_run *run)