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Tue, 07 Jul 2026 07:07:06 +0000 (GMT) Received: from smtpav06.fra02v.mail.ibm.com (smtpav06.fra02v.mail.ibm.com [10.20.54.105]) by smtprelay01.fra02v.mail.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 6677721p48562528 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 7 Jul 2026 07:07:02 GMT Received: from smtpav06.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 1348F20049; Tue, 7 Jul 2026 07:07:02 +0000 (GMT) Received: from smtpav06.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 82D1B2004D; Tue, 7 Jul 2026 07:07:00 +0000 (GMT) Received: from [9.67.174.189] (unknown [9.67.174.189]) by smtpav06.fra02v.mail.ibm.com (Postfix) with ESMTP; Tue, 7 Jul 2026 07:07:00 +0000 (GMT) Content-Type: multipart/alternative; boundary="------------DDvA9Bl9Fi0k0055kNDkeYN2" Message-ID: <1be96e32-ac9c-4160-9f2b-23eb29c22893@linux.ibm.com> Date: Tue, 7 Jul 2026 12:36:58 +0530 X-Mailing-List: linuxppc-dev@lists.ozlabs.org List-Id: List-Help: List-Owner: List-Post: List-Archive: , List-Subscribe: , , List-Unsubscribe: Precedence: list MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] powerpc/powernv: Cache OPAL check_token() results To: linuxppc-dev@lists.ozlabs.org, Shivang Upadhyay References: <20260626123534.396456-1-shivangu@linux.ibm.com> Content-Language: en-US Cc: Sourabh Jain From: Nikhil Kumar Singh In-Reply-To: <20260626123534.396456-1-shivangu@linux.ibm.com> X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: m0EsXGsPXBAP6s7ZabdvAx4CrZsfyWeW X-Proofpoint-Spam-Info: AW1haW4tMjYwNzA3MDA2NCBTYWx0ZWRfX/oAkgMv2zQpm Ed0jvNMJ8bCgnNG3ZsqhgO3pH7evoDcZ7ZlvnHnSKVMWioD43Q7QJaicmuv8FBJjd5VsVo3d1SF 5PEB6iycUAEs1o4w+uZuquT4QTSO/7U= X-Authority-Analysis: v=2.4 cv=DKW/JSNb c=1 sm=1 tr=0 ts=6a4ca59a cx=c_pps a=GFwsV6G8L6GxiO2Y/PsHdQ==:117 a=GFwsV6G8L6GxiO2Y/PsHdQ==:17 a=RAioF0-LDSMA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=RzCfie-kr_QcCd8fBx8p:22 a=r77TgQKjGQsHNAKrUKIA:9 a=6jT34AcC9rcdydElSecA:9 a=QEXdDO2ut3YA:10 a=VnNF1IyMAAAA:8 a=KdL_Wlk17mrYi_Q3vSQA:9 a=p6pgkoT_UOwxKcN3:21 a=_W_S_7VecoQA:10 X-Proofpoint-GUID: m0EsXGsPXBAP6s7ZabdvAx4CrZsfyWeW X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNzA3MDA2NCBTYWx0ZWRfX2+gOJ0dZ63xK 0uHXhf1wMi64Md/0/JBPv415M4Ap2rqFkrNhsK7pausKRGcFce2edz7wee3XI3WpxbJTacWrmvu a/gVXSTM+d1nLEEvHOXxGD0MRGR2g1s35M7YDEZm+7X0ZmH8LRvZSRCKKRZhTvx35mAbzPmrc1m 8uhN6wZ9iUDiMIJt8cvtQ3421y2yLSPRntvYkz+UaKRT7PhvWluzBuKNaeQrL4M/ZhOYjT766Ga 9hWxE5n141EJISxPpG1vx7EWGqL4Xmq3aCVIC1Cjh2+fGckashayfclB7xTYYNFTHtCxUbeXQde 7SfbTIzl2AS13O3Td2yACJRmwTwq2nUx+KDZkUCjr5yYj8XVmzX00S1UH/C/5vgypBAM0dLbF1G NgY7n8IHo4mvtjd8pyYVufP1GBRx75wVruloSsPWR+JRic8QlocVxLJPQAi/IxnvCZy5P9tVjDH MJmw4QlNGa9S/6tEj1Q== X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.134,FMLib:17.12.100.49 definitions=2026-07-07_01,2026-07-06_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 bulkscore=0 clxscore=1015 phishscore=0 impostorscore=0 priorityscore=1501 adultscore=0 lowpriorityscore=0 suspectscore=0 malwarescore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2607070064 This is a multi-part message in MIME format. --------------DDvA9Bl9Fi0k0055kNDkeYN2 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 26/06/26 18:05, Shivang Upadhyay wrote: > diff --git a/arch/powerpc/platforms/powernv/opal.c b/arch/powerpc/platforms/powernv/opal.c > index 1946dbdc9fa1..1e9cb5271ee7 100644 > --- a/arch/powerpc/platforms/powernv/opal.c > +++ b/arch/powerpc/platforms/powernv/opal.c > @@ -1125,6 +1125,36 @@ EXPORT_SYMBOL_GPL(opal_flash_read); > EXPORT_SYMBOL_GPL(opal_flash_write); > EXPORT_SYMBOL_GPL(opal_flash_erase); > EXPORT_SYMBOL_GPL(opal_prd_msg); > + > +/** > + * opal_check_token - Check if an OPAL call token is supported > + * @token: OPAL token number to check > + * > + * Returns 1 if supported, 0 if not. > + */ > +int64_t opal_check_token(uint64_t token) > +{ > + static u8 token_cache[OPAL_LAST]; > + enum { > + SUPP_UNKNOWN = 0, > + PRESENT, > + ABSENT > + }; > + > + if (token > OPAL_LAST) > + return 0; > + > + if (token_cache[token] == SUPP_UNKNOWN) { Hi Shivang, Thanks for the v2 patch. This is a great optimization and definitely helps reduce unnecessary overhead. I have one small suggestion. You can wrap the if (token_cache[token] == SUPP_UNKNOWN) check, as well as the if (token > OPAL_LAST) check above it, with unlikely(), since this function is in the hot path. Out-of-bounds tokens are very rare, and after the cache is populated, the SUPP_UNKNOWN condition is expected to be false in almost all cases. Wrapping these checks with unlikely() will help the compiler optimize branch prediction. Thanks, ~ Nikhil > + /* Do the actual opal_call here */ > + if (opal_check_token_call(token)) { > + token_cache[token] = PRESENT; > + } else { > + token_cache[token] = ABSENT; > + } > + } > + > + return (token_cache[token] == PRESENT); > +} > EXPORT_SYMBOL_GPL(opal_check_token); > > /* Convert a region of vmalloc memory to an opal sg list */ --------------DDvA9Bl9Fi0k0055kNDkeYN2 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: 7bit
On 26/06/26 18:05, Shivang Upadhyay wrote: 
diff --git a/arch/powerpc/platforms/powernv/opal.c b/arch/powerpc/platforms/powernv/opal.c
index 1946dbdc9fa1..1e9cb5271ee7 100644
--- a/arch/powerpc/platforms/powernv/opal.c
+++ b/arch/powerpc/platforms/powernv/opal.c
@@ -1125,6 +1125,36 @@ EXPORT_SYMBOL_GPL(opal_flash_read);
 EXPORT_SYMBOL_GPL(opal_flash_write);
 EXPORT_SYMBOL_GPL(opal_flash_erase);
 EXPORT_SYMBOL_GPL(opal_prd_msg);
+
+/**
+ * opal_check_token - Check if an OPAL call token is supported
+ * @token: OPAL token number to check
+ *
+ * Returns 1 if supported, 0 if not.
+ */
+int64_t opal_check_token(uint64_t token)
+{
+	static u8 token_cache[OPAL_LAST];
+	enum {
+		SUPP_UNKNOWN = 0,
+		PRESENT,
+		ABSENT
+	};
+
+	if (token > OPAL_LAST)
+		return 0;
+
+	if (token_cache[token] == SUPP_UNKNOWN) {

Hi Shivang,
Thanks for the v2 patch. This is a great optimization and definitely helps reduce unnecessary overhead. I have one small suggestion.

You can wrap the if (token_cache[token] == SUPP_UNKNOWN) check, as well as the if (token > OPAL_LAST) check above it, with unlikely(), since this function is in the hot path. Out-of-bounds tokens are very rare, and after the cache is populated, the SUPP_UNKNOWN condition is expected to be false in almost all cases. Wrapping these checks with unlikely() will help the compiler optimize branch prediction.

Thanks,
~ Nikhil

+		/* Do the actual opal_call here */
+		if (opal_check_token_call(token)) {
+			token_cache[token] = PRESENT;
+		} else {
+			token_cache[token] = ABSENT;
+		}
+	}
+
+	return (token_cache[token] == PRESENT);
+}
 EXPORT_SYMBOL_GPL(opal_check_token);
 
 /* Convert a region of vmalloc memory to an opal sg list */
--------------DDvA9Bl9Fi0k0055kNDkeYN2--