From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wg0-f51.google.com (mail-wg0-f51.google.com [74.125.82.51]) by kanga.kvack.org (Postfix) with ESMTP id D6A936B0099 for ; Mon, 3 Nov 2014 13:27:43 -0500 (EST) Received: by mail-wg0-f51.google.com with SMTP id l18so11671286wgh.38 for ; Mon, 03 Nov 2014 10:27:43 -0800 (PST) Received: from Galois.linutronix.de (Galois.linutronix.de. [2001:470:1f0b:db:abcd:42:0:1]) by mx.google.com with ESMTPS id ko8si25097303wjb.28.2014.11.03.10.27.42 for (version=TLSv1.2 cipher=RC4-SHA bits=128/128); Mon, 03 Nov 2014 10:27:42 -0800 (PST) Date: Mon, 3 Nov 2014 19:27:32 +0100 (CET) From: Thomas Gleixner Subject: Re: [PATCH v4 2/7] x86, mm, pat: Change reserve_memtype() to handle WT In-Reply-To: <1414450545-14028-3-git-send-email-toshi.kani@hp.com> Message-ID: References: <1414450545-14028-1-git-send-email-toshi.kani@hp.com> <1414450545-14028-3-git-send-email-toshi.kani@hp.com> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org List-ID: To: Toshi Kani Cc: hpa@zytor.com, mingo@redhat.com, akpm@linux-foundation.org, arnd@arndb.de, linux-mm@kvack.org, linux-kernel@vger.kernel.org, jgross@suse.com, stefan.bader@canonical.com, luto@amacapital.net, hmh@hmh.eng.br, yigal@plexistor.com, konrad.wilk@oracle.com On Mon, 27 Oct 2014, 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. > > Signed-off-by: Toshi Kani > Reviewed-by: Konrad Rzeszutek Wilk > --- > 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(); You already catch the cases with the hunk below at the entry of reserve_ram_pages_type(). So what's the point of the BUG()? If you are worried about other usage sites: This function should not at all be in arch/x86/include/asm/cacheflush.h. It's solely used by PAT, so we really should move it there before changing it. > default: > memtype_flags = _PGMT_DEFAULT; > break; > diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c > index db687c3..a214f5a 100644 > --- a/arch/x86/mm/pat.c > +++ b/arch/x86/mm/pat.c > @@ -289,6 +289,8 @@ 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 > @@ -300,6 +302,13 @@ 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); > @@ -349,6 +358,7 @@ 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 > @@ -368,10 +378,10 @@ 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; So until now we supported WB, UC- and UC and mapped WC to UC-. Now we map everything except WB to UC- Why feels that wrong without a comment explaining it? Thanks, tglx -- 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