From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Jones Date: Thu, 27 Apr 2023 11:41:38 +0200 Subject: [PATCH v2] lib: sbi: Ensure SBI extension is available Message-ID: <20230427094138.349029-1-ajones@ventanamicro.com> List-Id: To: opensbi@lists.infradead.org MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit 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 --- include/sbi/sbi_ecall.h | 14 ++++++++++++++ lib/sbi/sbi_ecall.c | 26 ++++++++++++++++++++++---- 2 files changed, 36 insertions(+), 4 deletions(-) diff --git a/include/sbi/sbi_ecall.h b/include/sbi/sbi_ecall.h index ff9bf8e2b435..9793019047e7 100644 --- a/include/sbi/sbi_ecall.h +++ b/include/sbi/sbi_ecall.h @@ -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, diff --git a/lib/sbi/sbi_ecall.c b/lib/sbi/sbi_ecall.c index 76a1ae9ab733..ad27b9b7e5cb 100644 --- a/lib/sbi/sbi_ecall.c +++ b/lib/sbi/sbi_ecall.c @@ -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) -- 2.39.2