From mboxrd@z Thu Jan 1 00:00:00 1970 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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 22E41C433FE for ; Mon, 21 Nov 2022 13:39:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231423AbiKUNjc (ORCPT ); Mon, 21 Nov 2022 08:39:32 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45308 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231367AbiKUNjF (ORCPT ); Mon, 21 Nov 2022 08:39:05 -0500 Received: from szxga03-in.huawei.com (szxga03-in.huawei.com [45.249.212.189]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 184F6636C; Mon, 21 Nov 2022 05:38:22 -0800 (PST) Received: from dggpemm500023.china.huawei.com (unknown [172.30.72.53]) by szxga03-in.huawei.com (SkyGuard) with ESMTP id 4NG7fq46ZczFqPg; Mon, 21 Nov 2022 21:34:59 +0800 (CST) Received: from dggpemm500001.china.huawei.com (7.185.36.107) by dggpemm500023.china.huawei.com (7.185.36.83) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.31; Mon, 21 Nov 2022 21:38:13 +0800 Received: from [10.67.111.195] (10.67.111.195) by dggpemm500001.china.huawei.com (7.185.36.107) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.31; Mon, 21 Nov 2022 21:38:13 +0800 Message-ID: Date: Mon, 21 Nov 2022 21:38:12 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.3.0 Subject: Re: [PATCH -next] RISC-V: KVM: optimize kvm_arch_hardware_enable() To: Andrew Jones CC: , , , , , , , , References: <20221121003915.2817102-1-chenlifu@huawei.com> <20221121105333.rap67cpmst3odiid@kamzik> From: chenlifu In-Reply-To: <20221121105333.rap67cpmst3odiid@kamzik> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 8bit X-Originating-IP: [10.67.111.195] X-ClientProxiedBy: dggems706-chm.china.huawei.com (10.3.19.183) To dggpemm500001.china.huawei.com (7.185.36.107) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 在 2022/11/21 18:53, Andrew Jones 写道: > On Mon, Nov 21, 2022 at 08:39:15AM +0800, Chen Lifu wrote: >> The values of CSR_HEDELEG and CSR_HIDELEG registers are constants, >> so change them from variables to macros. >> >> Signed-off-by: Chen Lifu >> --- >> arch/riscv/kvm/main.c | 31 +++++++++++++------------------ >> 1 file changed, 13 insertions(+), 18 deletions(-) >> >> diff --git a/arch/riscv/kvm/main.c b/arch/riscv/kvm/main.c >> index df2d8716851f..70196b03b6f9 100644 >> --- a/arch/riscv/kvm/main.c >> +++ b/arch/riscv/kvm/main.c >> @@ -12,10 +12,21 @@ >> #include >> #include >> #include >> #include >> >> +#define EXC_HEDELEG ((1UL << EXC_INST_MISALIGNED) | \ >> + (1UL << EXC_BREAKPOINT) | \ >> + (1UL << EXC_SYSCALL) | \ >> + (1UL << EXC_INST_PAGE_FAULT) | \ >> + (1UL << EXC_LOAD_PAGE_FAULT) | \ >> + (1UL << EXC_STORE_PAGE_FAULT)) >> + >> +#define IRQ_HIDELEG ((1UL << IRQ_VS_SOFT) | \ >> + (1UL << IRQ_VS_TIMER) | \ >> + (1UL << IRQ_VS_EXT)) >> + >> long kvm_arch_dev_ioctl(struct file *filp, >> unsigned int ioctl, unsigned long arg) >> { >> return -EINVAL; >> } >> @@ -30,29 +41,13 @@ int kvm_arch_hardware_setup(void *opaque) >> return 0; >> } >> >> int kvm_arch_hardware_enable(void) >> { >> - unsigned long hideleg, hedeleg; >> - >> - hedeleg = 0; >> - hedeleg |= (1UL << EXC_INST_MISALIGNED); >> - hedeleg |= (1UL << EXC_BREAKPOINT); >> - hedeleg |= (1UL << EXC_SYSCALL); >> - hedeleg |= (1UL << EXC_INST_PAGE_FAULT); >> - hedeleg |= (1UL << EXC_LOAD_PAGE_FAULT); >> - hedeleg |= (1UL << EXC_STORE_PAGE_FAULT); >> - csr_write(CSR_HEDELEG, hedeleg); >> - >> - hideleg = 0; >> - hideleg |= (1UL << IRQ_VS_SOFT); >> - hideleg |= (1UL << IRQ_VS_TIMER); >> - hideleg |= (1UL << IRQ_VS_EXT); >> - csr_write(CSR_HIDELEG, hideleg); >> - >> + csr_write(CSR_HEDELEG, EXC_HEDELEG); >> + csr_write(CSR_HIDELEG, IRQ_HIDELEG); >> csr_write(CSR_HCOUNTEREN, -1UL); >> - >> csr_write(CSR_HVIP, 0); >> >> return 0; >> } >> >> -- >> 2.37.1 >> > > I don't think this optimizes anything. I'm pretty sure the compiler will > load the input to csr_write() in the most efficient way it can, regardless > of using a constant or building the input out of constants. This could > maybe be considered a code cleanup, but, in this case, it's really in the > eye of the beholder. > > Thanks, > drew Thanks drew，you're right. I compared two version arch/riscv/kvm/main.o files, they are same.