From patchwork Tue Dec 7 09:41:09 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Leizhen (ThunderTown)" X-Patchwork-Id: 12695120 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 40045C433F5 for ; Tue, 7 Dec 2021 10:33:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To: Message-ID:Date:Subject:CC:To:From:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=A0OO41SJLhb/5LK5x/enjYSnVkJ3xKaysAtsFxsURkQ=; b=DSFVvgvxHFhPDr W+r7vOcoscUmztNiHZh4HiXY2pGI4bA0CJPMXPLpiDhWGvR1n65Yl2su/aXZznsOmU5qG5Q5qgKEZ wbS6pMrRkkNIyXkeQ7WbZTbQ9jiVOaPGloqXT7YE7sh8App2mwoWiibMZfNSzhOTpU2SF8/xhCElA yQUTIyDzimC6Kb1VWNvfIR+YPCsbuWjvQMZMEOK1Wg8emrg7IF8wAMqzQvmLTHUr7njQjkN+JFYZs CjiguDVi4qA2cCzJxsd7PWkcwP9MetkmFoKDY4cgbe7ujlebW3w8P/f2S+eYJOynywQlkFaR539zG NwfK7sGP2rCEA8x1i84g==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1muXkR-0082Lq-Jy; Tue, 07 Dec 2021 10:31:01 +0000 Received: from szxga03-in.huawei.com ([45.249.212.189]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1muX3N-007s4R-8Q for linux-arm-kernel@lists.infradead.org; Tue, 07 Dec 2021 09:46:31 +0000 Received: from dggpemm500024.china.huawei.com (unknown [172.30.72.55]) by szxga03-in.huawei.com (SkyGuard) with ESMTP id 4J7b3l1csszXdWF; Tue, 7 Dec 2021 17:44:19 +0800 (CST) Received: from dggpemm500006.china.huawei.com (7.185.36.236) by dggpemm500024.china.huawei.com (7.185.36.203) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2308.20; Tue, 7 Dec 2021 17:46:23 +0800 Received: from thunder-town.china.huawei.com (10.174.178.55) by dggpemm500006.china.huawei.com (7.185.36.236) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2308.20; Tue, 7 Dec 2021 17:46:23 +0800 From: Zhen Lei To: Will Deacon , Robin Murphy , "Joerg Roedel" , , , CC: Zhen Lei Subject: [PATCH v3 1/1] iommu/arm-smmu-v3: Simplify useless instructions in arm_smmu_cmdq_build_cmd() Date: Tue, 7 Dec 2021 17:41:09 +0800 Message-ID: <20211207094109.1962-2-thunder.leizhen@huawei.com> X-Mailer: git-send-email 2.26.0.windows.1 In-Reply-To: <20211207094109.1962-1-thunder.leizhen@huawei.com> References: <20211207094109.1962-1-thunder.leizhen@huawei.com> MIME-Version: 1.0 X-Originating-IP: [10.174.178.55] X-ClientProxiedBy: dggems703-chm.china.huawei.com (10.3.19.180) To dggpemm500006.china.huawei.com (7.185.36.236) X-CFilter-Loop: Reflected X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20211207_014629_690609_F8852C7C X-CRM114-Status: GOOD ( 14.15 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Although the parameter 'cmd' is always passed by a local array variable, and only this function modifies it, the compiler does not know this. Every time the 'cmd' variable is updated, a memory write operation is generated. This generates many useless instruction operations. To guide the compiler for proper optimization, 'cmd' is defined as a local array variable, and copied to the output parameter at a time when the function is returned. The optimization effect can be viewed by running the "size arm-smmu-v3.o" command. Before: text data bss dec hex 28246 1332 56 29634 73c2 After: text data bss dec hex 28134 1332 56 29522 7352 For example: cmd[0] = FIELD_PREP(CMDQ_0_OP, ent->opcode); case CMDQ_OP_TLBI_EL2_VA: cmd[0] |= FIELD_PREP(CMDQ_TLBI_0_NUM, ent->tlbi.num); cmd[0] |= FIELD_PREP(CMDQ_TLBI_0_SCALE, ent->tlbi.scale); cmd[0] |= FIELD_PREP(CMDQ_TLBI_0_ASID, ent->tlbi.asid); cmd[1] |= FIELD_PREP(CMDQ_TLBI_1_LEAF, ent->tlbi.leaf); cmd[1] |= FIELD_PREP(CMDQ_TLBI_1_TTL, ent->tlbi.ttl); cmd[1] |= FIELD_PREP(CMDQ_TLBI_1_TG, ent->tlbi.tg); cmd[1] |= ent->tlbi.addr & CMDQ_TLBI_1_VA_MASK; Before: Each "cmd[0] |=" or "cmd[1] |=" operation generates a "str" instruction, sum = 8. ldrb w4, [x1, #8] //w4 = ent->tlbi.num ubfiz x4, x4, #12, #5 mov w0, #0x0 orr x4, x4, x3 str x4, [x2] autiasp ldrb w3, [x1, #9] //w3 = ent->tlbi.scale ubfiz x3, x3, #20, #5 orr x3, x3, x4 str x3, [x2] ldrh w4, [x1, #10] //w4 = ent->tlbi.asid orr x3, x3, x4, lsl #48 str x3, [x2] ldrb w3, [x1, #14] //w3 = ent->tlbi.leaf str x3, [x2, #8] ldrb w4, [x1, #15] //w4 = ent->tlbi.ttl ubfiz x4, x4, #8, #2 orr x4, x4, x3 str x4, [x2, #8] ldrb w3, [x1, #16] //ent->tlbi.tg ubfiz x3, x3, #10, #2 orr x3, x3, x4 str x3, [x2, #8] ldr x1, [x1, #24] //ent->tlbi.addr and x1, x1, #0xfffffffffffff000 orr x1, x1, x3 str x1, [x2, #8] ret After: All "cmd[0] |=" and "cmd[1] |=" operations generate a "stp" instruction, sum = 1. 3e8: mov w0, #0x0 autiasp stp x2, x1, [x3] ret bti j 3fc: ldrb w5, [x1, #8] //w5 = ent->tlbi.num mov x2, #0x22 //x2 = ent->opcode = CMDQ_0_OP ldrb w6, [x1, #9] //w6 = ent->tlbi.scale ubfiz x5, x5, #12, #5 ldrb w0, [x1, #16] //w0 = ent->tlbi.tg orr x5, x5, x2 ldrb w7, [x1, #15] //w7 = ent->tlbi.ttl ldr x4, [x1, #24] //x4 = ent->tlbi.addr ubfiz x0, x0, #10, #2 ldrh w2, [x1, #10] //w2 = ent->tlbi.asid ubfiz x6, x6, #20, #5 ldrb w8, [x1, #14] //w8 = ent->tlbi.leaf and x4, x4, #0xfffffffffffff000 ubfiz x1, x7, #8, #2 orr x1, x0, x1 orr x2, x6, x2, lsl #48 orr x0, x4, x8 orr x2, x2, x5 orr x1, x1, x0 b 3e8 Signed-off-by: Zhen Lei --- drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c index f5848b351b19359..e55dfc14cac6005 100644 --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c @@ -234,10 +234,12 @@ static int queue_remove_raw(struct arm_smmu_queue *q, u64 *ent) } /* High-level queue accessors */ -static int arm_smmu_cmdq_build_cmd(u64 *cmd, struct arm_smmu_cmdq_ent *ent) +static int arm_smmu_cmdq_build_cmd(u64 *out_cmd, struct arm_smmu_cmdq_ent *ent) { - memset(cmd, 0, 1 << CMDQ_ENT_SZ_SHIFT); - cmd[0] |= FIELD_PREP(CMDQ_0_OP, ent->opcode); + int i; + u64 cmd[CMDQ_ENT_DWORDS] = {0}; + + cmd[0] = FIELD_PREP(CMDQ_0_OP, ent->opcode); switch (ent->opcode) { case CMDQ_OP_TLBI_EL2_ALL: @@ -332,6 +334,9 @@ static int arm_smmu_cmdq_build_cmd(u64 *cmd, struct arm_smmu_cmdq_ent *ent) return -ENOENT; } + for (i = 0; i < CMDQ_ENT_DWORDS; i++) + out_cmd[i] = cmd[i]; + return 0; }