@@ -20,10 +20,24 @@
struct sbi_trap_regs;
struct sbi_trap_info;
+/*
+ * sbi_ext_status is used to optimize lookups of extensions which have
+ * single extension IDs, i.e. extid_start == extid_end. The status is
+ * set after the first call of the extension's probe function (if it
+ * has one) in order to avoid repeating the probe call on later lookups.
+ * Extensions with more than one ID should ensure their probe functions
+ * are fast, perhaps by caching responses.
+ */
+enum sbi_ext_status {
+ SBI_EXT_AVAILABLE = 1,
+ SBI_EXT_UNAVAILABLE,
+};
+
struct sbi_ecall_extension {
struct sbi_dlist head;
unsigned long extid_start;
unsigned long extid_end;
+ enum sbi_ext_status status;
int (* probe)(unsigned long extid, unsigned long *out_val);
int (* handle)(unsigned long extid, unsigned long funcid,
const struct sbi_trap_regs *regs,
@@ -42,16 +42,34 @@ static SBI_LIST_HEAD(ecall_exts_list);
struct sbi_ecall_extension *sbi_ecall_find_extension(unsigned long extid)
{
- struct sbi_ecall_extension *t, *ret = NULL;
+ struct sbi_ecall_extension *t;
+ unsigned long out_val;
sbi_list_for_each_entry(t, &ecall_exts_list, head) {
+ bool use_status = t->extid_start == t->extid_end;
+
if (t->extid_start <= extid && extid <= t->extid_end) {
- ret = t;
- break;
+ if (use_status) {
+ if (t->status == SBI_EXT_AVAILABLE)
+ return t;
+ if (t->status == SBI_EXT_UNAVAILABLE)
+ return NULL;
+ }
+
+ if (t->probe && (t->probe(extid, &out_val) || !out_val)) {
+ if (use_status)
+ t->status = SBI_EXT_UNAVAILABLE;
+ return NULL;
+ }
+
+ if (use_status)
+ t->status = SBI_EXT_AVAILABLE;
+
+ return t;
}
}
- return ret;
+ return NULL;
}
int sbi_ecall_register_extension(struct sbi_ecall_extension *ext)
Ensure attempts to invoke SBI extension functions fail with SBI_ERR_NOT_SUPPORTED when the extension's probe function has reported that the extension is not available. By adding a new status member to the extension, which has three states (uninitialized, available, unavailable), we can ensure that the probe functions of single ID extensions, i.e. extid_start == extid_end, are only invoked once, lazily, upon first use. Extensions that have multiple IDs cannot use a single status field to avoid making probe calls, as probe functions are extension ID specific. It's expected that these multi-ID extension probe functions implement their own optimizations in order to ensure extension lookups are fast. Signed-off-by: Andrew Jones <ajones@ventanamicro.com> --- include/sbi/sbi_ecall.h | 14 ++++++++++++++ lib/sbi/sbi_ecall.c | 26 ++++++++++++++++++++++---- 2 files changed, 36 insertions(+), 4 deletions(-)