From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-la0-f49.google.com (mail-la0-f49.google.com [209.85.215.49]) by kanga.kvack.org (Postfix) with ESMTP id 22F466B0036 for ; Wed, 10 Sep 2014 14:26:46 -0400 (EDT) Received: by mail-la0-f49.google.com with SMTP id pv20so894034lab.22 for ; Wed, 10 Sep 2014 11:26:45 -0700 (PDT) Received: from mail-lb0-f175.google.com (mail-lb0-f175.google.com [209.85.217.175]) by mx.google.com with ESMTPS id l2si22431986lag.111.2014.09.10.11.26.43 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Wed, 10 Sep 2014 11:26:44 -0700 (PDT) Received: by mail-lb0-f175.google.com with SMTP id v6so5408220lbi.34 for ; Wed, 10 Sep 2014 11:26:43 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <1410367910-6026-3-git-send-email-toshi.kani@hp.com> References: <1410367910-6026-1-git-send-email-toshi.kani@hp.com> <1410367910-6026-3-git-send-email-toshi.kani@hp.com> From: Andy Lutomirski Date: Wed, 10 Sep 2014 11:26:23 -0700 Message-ID: Subject: Re: [PATCH v2 2/6] x86, mm, pat: Change reserve_memtype() to handle WT Content-Type: text/plain; charset=UTF-8 Sender: owner-linux-mm@kvack.org List-ID: To: Toshi Kani Cc: "H. Peter Anvin" , Thomas Gleixner , Ingo Molnar , Andrew Morton , Arnd Bergmann , "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" , Juergen Gross , Stefan Bader , Henrique de Moraes Holschuh , Yigal Korman , Konrad Rzeszutek Wilk On Wed, Sep 10, 2014 at 9:51 AM, Toshi Kani wrote: > This patch changes reserve_memtype() to handle the WT cache mode. > When PAT is not enabled, it continues to set UC- to *new_type for > any non-WB request. > > When a target range is RAM, reserve_ram_pages_type() fails for WT > for now. This function may not reserve a RAM range for WT since > reserve_ram_pages_type() uses the page flags limited to three memory > types, WB, WC and UC. Should it fail if WT is unavailable due to errata? More generally, how are all of the do_something_wc / do_something_wt / do_something_nocache helpers supposed to handle unsupported types? --Andy > > Signed-off-by: Toshi Kani > --- > arch/x86/include/asm/cacheflush.h | 4 ++++ > arch/x86/mm/pat.c | 16 +++++++++++++--- > 2 files changed, 17 insertions(+), 3 deletions(-) > > diff --git a/arch/x86/include/asm/cacheflush.h b/arch/x86/include/asm/cacheflush.h > index 157644b..c912680 100644 > --- a/arch/x86/include/asm/cacheflush.h > +++ b/arch/x86/include/asm/cacheflush.h > @@ -53,6 +53,10 @@ static inline void set_page_memtype(struct page *pg, > case _PAGE_CACHE_MODE_WB: > memtype_flags = _PGMT_WB; > break; > + case _PAGE_CACHE_MODE_WT: > + case _PAGE_CACHE_MODE_WP: > + pr_err("set_page_memtype: unsupported cachemode %d\n", memtype); > + BUG(); > default: > memtype_flags = _PGMT_DEFAULT; > break; > diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c > index 598d7c7..7644967 100644 > --- a/arch/x86/mm/pat.c > +++ b/arch/x86/mm/pat.c > @@ -268,6 +268,8 @@ static int pat_pagerange_is_ram(resource_size_t start, resource_size_t end) > > /* > * For RAM pages, we use page flags to mark the pages with appropriate type. > + * The page flags are currently limited to three types, WB, WC and UC. Hence, > + * any request to WT or WP will fail with -EINVAL. > * Here we do two pass: > * - Find the memtype of all the pages in the range, look for any conflicts > * - In case of no conflicts, set the new memtype for pages in the range > @@ -279,6 +281,13 @@ static int reserve_ram_pages_type(u64 start, u64 end, > struct page *page; > u64 pfn; > > + if ((req_type == _PAGE_CACHE_MODE_WT) || > + (req_type == _PAGE_CACHE_MODE_WP)) { > + if (new_type) > + *new_type = _PAGE_CACHE_MODE_UC_MINUS; > + return -EINVAL; > + } > + > if (req_type == _PAGE_CACHE_MODE_UC) { > /* We do not support strong UC */ > WARN_ON_ONCE(1); > @@ -328,6 +337,7 @@ static int free_ram_pages_type(u64 start, u64 end) > * - _PAGE_CACHE_MODE_WC > * - _PAGE_CACHE_MODE_UC_MINUS > * - _PAGE_CACHE_MODE_UC > + * - _PAGE_CACHE_MODE_WT > * > * If new_type is NULL, function will return an error if it cannot reserve the > * region with req_type. If new_type is non-NULL, function will return > @@ -347,10 +357,10 @@ int reserve_memtype(u64 start, u64 end, enum page_cache_mode req_type, > if (!pat_enabled) { > /* This is identical to page table setting without PAT */ > if (new_type) { > - if (req_type == _PAGE_CACHE_MODE_WC) > - *new_type = _PAGE_CACHE_MODE_UC_MINUS; > + if (req_type == _PAGE_CACHE_MODE_WB) > + *new_type = _PAGE_CACHE_MODE_WB; > else > - *new_type = req_type; > + *new_type = _PAGE_CACHE_MODE_UC_MINUS; > } > return 0; > } -- Andy Lutomirski AMA Capital Management, LLC -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org