Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757740AbbEVPYA (ORCPT ); Fri, 22 May 2015 11:24:00 -0400 Received: from g2t2352.austin.hp.com ([15.217.128.51]:32968 "EHLO g2t2352.austin.hp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756992AbbEVPXy (ORCPT ); Fri, 22 May 2015 11:23:54 -0400 Message-ID: <1432307070.3184.19.camel@misato.fc.hp.com> Subject: Re: [PATCH v9 7/10] x86, mm, asm: Add WT support to set_page_memtype() From: Toshi Kani To: Thomas Gleixner Cc: hpa@zytor.com, mingo@redhat.com, akpm@linux-foundation.org, arnd@arndb.de, linux-mm@kvack.org, linux-kernel@vger.kernel.org, x86@kernel.org, linux-nvdimm@ml01.01.org, jgross@suse.com, stefan.bader@canonical.com, luto@amacapital.net, hmh@hmh.eng.br, yigal@plexistor.com, konrad.wilk@oracle.com, Elliott@hp.com, mcgrof@suse.com, hch@lst.de Date: Fri, 22 May 2015 09:04:30 -0600 In-Reply-To: References: <1431551151-19124-1-git-send-email-toshi.kani@hp.com> <1431551151-19124-8-git-send-email-toshi.kani@hp.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.10.4 (3.10.4-4.fc20) Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4080 Lines: 125 On Fri, 2015-05-22 at 09:35 +0200, Thomas Gleixner wrote: > On Wed, 13 May 2015, Toshi Kani wrote: > > + * X86 PAT uses page flags arch_1 and uncached together to keep track of > > + * memory type of pages that have backing page struct. X86 PAT supports 4 > > + * different memory types, _PAGE_CACHE_MODE_WT, _PAGE_CACHE_MODE_WC, > > + * _PAGE_CACHE_MODE_UC_MINUS and _PAGE_CACHE_MODE_WB where page's memory > > + * type has not been changed from its default. > > This is a horrible sentence. > > * X86 PAT supports 4 different memory types: > * - _PAGE_CACHE_MODE_WB > * - _PAGE_CACHE_MODE_WC > * - _PAGE_CACHE_MODE_UC_MINUS > * - _PAGE_CACHE_MODE_WT > * > * _PAGE_CACHE_MODE_WB is the default type. > */ > Hmm? Sounds good. I will update as suggested. > > * Note we do not support _PAGE_CACHE_MODE_UC here. > > This can be removed as it is completely redundant. Will remove this sentence. > > */ > > > > -#define _PGMT_DEFAULT 0 > > +#define _PGMT_WB 0 /* default */ > > We just established two lines above that this is the default Will remove this comment as well. > > #define _PGMT_WC (1UL << PG_arch_1) > > #define _PGMT_UC_MINUS (1UL << PG_uncached) > > -#define _PGMT_WB (1UL << PG_uncached | 1UL << PG_arch_1) > > +#define _PGMT_WT (1UL << PG_uncached | 1UL << PG_arch_1) > > #define _PGMT_MASK (1UL << PG_uncached | 1UL << PG_arch_1) > > #define _PGMT_CLEAR_MASK (~_PGMT_MASK) > > > > @@ -88,14 +88,14 @@ static inline enum page_cache_mode get_page_memtype(struct page *pg) > > { > > unsigned long pg_flags = pg->flags & _PGMT_MASK; > > > > - if (pg_flags == _PGMT_DEFAULT) > > - return -1; > > + if (pg_flags == _PGMT_WB) > > + return _PAGE_CACHE_MODE_WB; > > else if (pg_flags == _PGMT_WC) > > return _PAGE_CACHE_MODE_WC; > > else if (pg_flags == _PGMT_UC_MINUS) > > return _PAGE_CACHE_MODE_UC_MINUS; > > else > > - return _PAGE_CACHE_MODE_WB; > > + return _PAGE_CACHE_MODE_WT; > > } > > > > static inline void set_page_memtype(struct page *pg, > > @@ -112,11 +112,12 @@ static inline void set_page_memtype(struct page *pg, > > case _PAGE_CACHE_MODE_UC_MINUS: > > memtype_flags = _PGMT_UC_MINUS; > > break; > > - case _PAGE_CACHE_MODE_WB: > > - memtype_flags = _PGMT_WB; > > + case _PAGE_CACHE_MODE_WT: > > + memtype_flags = _PGMT_WT; > > break; > > + case _PAGE_CACHE_MODE_WB: > > default: > > - memtype_flags = _PGMT_DEFAULT; > > + memtype_flags = _PGMT_WB; /* default */ > > What's the value of that comment? > > default: > /* default */ I was trying to preserve the original name of "_PGMT_DEFAULT" with the comment because _PGMT_WB takes the place of _PGMT_DEFAULT with this change. But I agree that this may be redundant. I will remove this comment as well. > Aside of the, please do not use tail comments. They make code harder > to parse. Got it. > > /* > > * For RAM pages, we use page flags to mark the pages with appropriate type. > > - * The page flags are limited to three types, WB, WC and UC-. > > - * WT and WP requests fail with -EINVAL, and UC gets redirected to UC-. > > + * The page flags are limited to four types, WB (default), WC, WT and UC-. > > + * WP request fails with -EINVAL, and UC gets redirected to UC-. > > > + * A new memtype can only be set to the default memtype WB. > > I have no idea what that line means. I will change it to "Setting a new memory type is only allowed to a page mapped with the default WB type." > > @@ -582,13 +583,6 @@ static enum page_cache_mode lookup_memtype(u64 paddr) > > struct page *page; > > page = pfn_to_page(paddr >> PAGE_SHIFT); > > rettype = get_page_memtype(page); > > return get_page_memtype(page); > > And while you are at it please add the missing newline between the > variable declaration and code. Will do. Thanks, -Toshi -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/