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 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 1E40CCD4F53 for ; Fri, 22 Sep 2023 10:26:57 +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-Type: Content-Transfer-Encoding:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:From:References:Cc:To:Subject: MIME-Version:Date:Message-ID:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=qi4EPUW591hSSOpzb+EaVaVKH9bBhZiHOmP2OYWKHQA=; b=Y0iTN8eBDRuioP pJA3uDI3dXxGUvYZiMKBykqlgRopVhBeMnvYrh0rCkC7eStSajzYqNK8rNcTuHvvfh4ZUIJVKYGUf JSHQtuprqOR8cMQoXG7Ifih/icA4bbRZ/+mIbNsfcCCZvfWa8nwQ54hea1Q+qQ3weCSbGnYtoiGw9 4/JehbYuqKhzLBdoy8vfLUL6lwp+7TEcZ8RhNzgGGpeMTZSl4VOtsipavV/wNuF0rN2PqWnV0YV5i bDdpCimOINKnk/JmZO3L83IFkt31e+Wr/r595f6Ro1f6IWjHtVu0wWFqnm2U97Zy3qx5urA+FiMzy 3hVFzenDaePtcfK4LFOw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.96 #2 (Red Hat Linux)) id 1qjdMj-008q1r-09; Fri, 22 Sep 2023 10:26:29 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.96 #2 (Red Hat Linux)) id 1qjdMg-008pz9-13 for linux-arm-kernel@lists.infradead.org; Fri, 22 Sep 2023 10:26:27 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 6CD8CDA7; Fri, 22 Sep 2023 03:27:02 -0700 (PDT) Received: from [10.57.92.170] (unknown [10.57.92.170]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 2E0263F67D; Fri, 22 Sep 2023 03:26:23 -0700 (PDT) Message-ID: Date: Fri, 22 Sep 2023 11:26:21 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:102.0) Gecko/20100101 Thunderbird/102.15.1 Subject: Re: [PATCH 05/37] arm64: Add cpus_have_final_boot_cap() To: Mark Rutland Cc: linux-arm-kernel@lists.infradead.org, ardb@kernel.org, bertrand.marquis@arm.com, boris.ostrovsky@oracle.com, broonie@kernel.org, catalin.marinas@arm.com, daniel.lezcano@linaro.org, james.morse@arm.com, jgross@suse.com, maz@kernel.org, oliver.upton@linux.dev, pcc@google.com, sstabellini@kernel.org, tglx@linutronix.de, vladimir.murzin@arm.com, will@kernel.org References: <20230919092850.1940729-1-mark.rutland@arm.com> <20230919092850.1940729-6-mark.rutland@arm.com> <55c9f428-b715-a2ae-5b89-d125a0104ea3@arm.com> From: Suzuki K Poulose In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20230922_032626_459026_17D37BC3 X-CRM114-Status: GOOD ( 29.64 ) 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: , Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 21/09/2023 17:36, Mark Rutland wrote: > On Thu, Sep 21, 2023 at 10:13:31AM +0100, Suzuki K Poulose wrote: >> Hi Mark >> >> On 19/09/2023 10:28, Mark Rutland wrote: >>> The cpus_have_final_boot_cap() function can be used to test a cpucap >> >> nit: cpus_have_final_cap() > > Thanks; fixed now. > >>> while also verifying that we do not consume the cpucap until system >>> capabilities have been finalized. It would be helpful if we could do >>> likewise for boot cpucaps. >>> >>> This patch adds a new cpus_have_final_boot_cap() helper which can be >>> used to test a cpucap while also verifying that boot capabilities have >>> been finalized. Users will be added in subsequent patches. >>> >>> Signed-off-by: Mark Rutland >>> Cc: Catalin Marinas >>> Cc: Mark Brown >>> Cc: Suzuki K Poulose >>> Cc: Will Deacon >>> --- >>> arch/arm64/include/asm/cpufeature.h | 27 +++++++++++++++++++++++++-- >>> 1 file changed, 25 insertions(+), 2 deletions(-) >>> >>> diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h >>> index 7d5317bc2429f..e832b86c6b57f 100644 >>> --- a/arch/arm64/include/asm/cpufeature.h >>> +++ b/arch/arm64/include/asm/cpufeature.h >>> @@ -438,6 +438,11 @@ unsigned long cpu_get_elf_hwcap2(void); >>> #define cpu_set_named_feature(name) cpu_set_feature(cpu_feature(name)) >>> #define cpu_have_named_feature(name) cpu_have_feature(cpu_feature(name)) >>> +static __always_inline bool boot_capabilities_finalized(void) >>> +{ >>> + return alternative_has_cap_likely(ARM64_ALWAYS_BOOT); >>> +} >>> + >>> static __always_inline bool system_capabilities_finalized(void) >>> { >>> return alternative_has_cap_likely(ARM64_ALWAYS_SYSTEM); >>> @@ -473,8 +478,26 @@ static __always_inline bool __cpus_have_const_cap(int num) >>> /* >>> * Test for a capability without a runtime check. >>> * >>> - * Before capabilities are finalized, this will BUG(). >>> - * After capabilities are finalized, this is patched to avoid a runtime check. >>> + * Before boot capabilities are finalized, this will BUG(). >>> + * After boot capabilities are finalized, this is patched to avoid a runtime >>> + * check. >>> + * >>> + * @num must be a compile-time constant. >>> + */ >>> +static __always_inline bool cpus_have_final_boot_cap(int num) >>> +{ >>> + if (boot_capabilities_finalized()) >> >> Does this need to make sure the cap is really a "BOOT" cap ? It is a bit of >> an overkill, but prevents users from incorrectly assuming the cap is >> finalised ? > > Do you have an idea in mind for how to do that? > > I had also wanted that, but we don't have the information available when > compiling the callsites today since that's determined by the > arm64_cpu_capabilities::type flags. > > We could us an alternative callback for boot_capabilities_finalized() that > goes and checks the arm64_cpu_capabilities::type flags, but that doesn't seem > very nice. > Thats what I had initially in mind, and is why I called it an overkill. But may be another option is to have a different alternative construct for all capabilities, which defaults to BUG() and then patched to "false" or "true" based on the real status ? This may be more complicated. > Otherwise, given this only has a few users, I could have those directly use: > > BUG_ON(!boot_capabilities_finalized()); > > ... and remove cpus_have_final_boot_cap() for now? I don't think that is necessary. We could keep your patch as is, if we can't verify the boot capability easily. Suzuki > > Thanks, > Mark. > >> >> >> Suzuki >> >>> + return __cpus_have_const_cap(num); >>> + else >>> + BUG(); >>> +} >>> + >>> +/* >>> + * Test for a capability without a runtime check. >>> + * >>> + * Before system capabilities are finalized, this will BUG(). >>> + * After system capabilities are finalized, this is patched to avoid a runtime >>> + * check. >>> * >>> * @num must be a compile-time constant. >>> */ >> _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel