From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 98F7920400C for ; Fri, 18 Oct 2024 17:07:27 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1729271249; cv=none; b=M//pOw6wkK90F2bPuIvToJHy3L14oT9Fry+TlPuWFwkuhX/K3vZBYkCJkN7i35Vq0ze2F+60FJCN5qGmisU4E1vdzDHs3O4NCXl5WjjFZFQos3lEDLBXNEUeAwf4BX+b4VnuhzuoFF+PlJ6U4LnF65mR4uPmH1ivRnD6jeA6JvY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1729271249; c=relaxed/simple; bh=nyJcBtVOQUIERqDCjN4CNZkSIwDbjHwudrH+HgGuNJA=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=tuOlykOiWK5mRKyZSx2Qqy+4tifHeKJjJ4hXvXb1bUFNupqcFtvQnKJiXAUi9zp7opm+RNOgHFG8CU0GHsL+n0kGHXdY/TzdX2OiNDxfVBFdfycjs2JHBcepArjpjWdlcc83bs6ftP4SLlFi0abHz8p0/oeCeZ/hp7XR7xIsORM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com 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 B392915BF; Fri, 18 Oct 2024 10:07:56 -0700 (PDT) Received: from [10.1.196.28] (eglon.cambridge.arm.com [10.1.196.28]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 401733F528; Fri, 18 Oct 2024 10:07:23 -0700 (PDT) Message-ID: Date: Fri, 18 Oct 2024 18:07:19 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v5 04/40] x86/resctrl: Use schema type to determine how to parse schema values Content-Language: en-GB To: Tony Luck Cc: x86@kernel.org, linux-kernel@vger.kernel.org, Fenghua Yu , Reinette Chatre , Thomas Gleixner , Ingo Molnar , Borislav Petkov , H Peter Anvin , Babu Moger , shameerali.kolothum.thodi@huawei.com, D Scott Phillips OS , carl@os.amperecomputing.com, lcherian@marvell.com, bobo.shaobowang@huawei.com, tan.shaopeng@fujitsu.com, baolin.wang@linux.alibaba.com, Jamie Iles , Xin Hao , peternewman@google.com, dfustini@baylibre.com, amitsinght@marvell.com, David Hildenbrand , Rex Nie , Dave Martin , Shaopeng Tan References: <20241004180347.19985-1-james.morse@arm.com> <20241004180347.19985-5-james.morse@arm.com> From: James Morse In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Hi Tony, On 16/10/2024 00:15, Tony Luck wrote: > On Fri, Oct 04, 2024 at 06:03:11PM +0000, James Morse wrote: >> +static ctrlval_parser_t *get_parser(struct rdt_resource *r) >> +{ >> + switch (r->schema_fmt) { >> + case RESCTRL_SCHEMA_BITMAP: >> + return &parse_cbm; >> + case RESCTRL_SCHEMA_RANGE: >> + return &parse_bw; >> + } >> + >> + return NULL; >> +} > > Is it really worth making this a helper function? It's only > used once. Moved. This was just to avoid bloating the caller with boiler-plate. >> + >> /* >> * For each domain in this resource we expect to find a series of: >> * id=mask >> @@ -204,6 +225,7 @@ int parse_cbm(struct rdt_parse_data *data, struct resctrl_schema *s, >> static int parse_line(char *line, struct resctrl_schema *s, >> struct rdtgroup *rdtgrp) >> { >> + ctrlval_parser_t *parse_ctrlval = get_parser(s->res); > > No check to see if get_parser() returned NULL. No - but you must have passed it a non-existant enum value for that to happen, so we're already in memory corruption territory. (I probably should have made get_parser() WARN_ON_ONCE() when returning NULL) >> enum resctrl_conf_type t = s->conf_type; >> struct resctrl_staged_config *cfg; >> struct rdt_resource *r = s->res; >> @@ -235,7 +257,7 @@ static int parse_line(char *line, struct resctrl_schema *s, >> if (d->hdr.id == dom_id) { >> data.buf = dom; >> data.rdtgrp = rdtgrp; >> - if (r->parse_ctrlval(&data, s, d)) >> + if (parse_ctrlval(&data, s, d)) >> return -EINVAL; > > Without the helper this could be: > > switch (r->schema_fmt) { > case RESCTRL_SCHEMA_BITMAP: > if (parse_cbm(&data, s, d)) > return -EINVAL; > break; > case RESCTRL_SCHEMA_RANGE: > if (parse_bw(&data, s, d)) > return -EINVAL; > break; > default: > WARN_ON_ONCE(1); > return -EINVAL; > } I'd prefer the switch statement to have no default so that it triggers a compiler warning when future enum entries are added. This way the compiler can find cases where a new schema format missed a bit - it doesn't need booting the result on hardware to trigger a warning. To avoid 'break' in a loop not breaking out of the loop, and to avoid bloating the loop I've kept the function pointer so the non-existant enum case is handled with the rest of the errors at the top of the function: | /* Walking r->domains, ensure it can't race with cpuhp */ | lockdep_assert_cpus_held(); | | switch (r->schema_fmt) { | case RESCTRL_SCHEMA_BITMAP: | parse_ctrlval = &parse_cbm; | break; | case RESCTRL_SCHEMA_RANGE: | parse_ctrlval = &parse_bw; | break; | } | | if (WARN_ON_ONCE(!parse_ctrlval)) | return -EINVAL; | | if (rdtgrp->mode == RDT_MODE_PSEUDO_LOCKSETUP && Thanks, James