From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932306AbdKOKoi (ORCPT ); Wed, 15 Nov 2017 05:44:38 -0500 Received: from mx1.redhat.com ([209.132.183.28]:50494 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932136AbdKOKo3 (ORCPT ); Wed, 15 Nov 2017 05:44:29 -0500 Subject: Re: [PATCH v5 1/2] x86/mm: add a function to check if a pfn is UC/UC- To: Haozhong Zhang , kvm@vger.kernel.org, x86@kernel.org Cc: linux-kernel@vger.kernel.org, Paolo Bonzini , rkrcmar@redhat.com, Xiao Guangrong , Dan Williams , ivan.d.cuevas.escareno@intel.com, karthik.kumar@intel.com, Konrad Rzeszutek Wilk , Olif Chapman , Mikulas Patocka , Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , Borislav Petkov , Tom Lendacky References: <20171108075630.16991-1-haozhong.zhang@intel.com> <20171108075630.16991-2-haozhong.zhang@intel.com> From: David Hildenbrand Organization: Red Hat GmbH Message-ID: Date: Wed, 15 Nov 2017 11:44:24 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.4.0 MIME-Version: 1.0 In-Reply-To: <20171108075630.16991-2-haozhong.zhang@intel.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.30]); Wed, 15 Nov 2017 10:44:29 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 08.11.2017 08:56, Haozhong Zhang wrote: > It will be used by KVM to check whether a pfn should be > mapped to guest as UC. > > Signed-off-by: Haozhong Zhang > --- > arch/x86/include/asm/pat.h | 2 ++ > arch/x86/mm/pat.c | 16 ++++++++++++++++ > 2 files changed, 18 insertions(+) > > diff --git a/arch/x86/include/asm/pat.h b/arch/x86/include/asm/pat.h > index fffb2794dd89..fabb0cf00e77 100644 > --- a/arch/x86/include/asm/pat.h > +++ b/arch/x86/include/asm/pat.h > @@ -21,4 +21,6 @@ int io_reserve_memtype(resource_size_t start, resource_size_t end, > > void io_free_memtype(resource_size_t start, resource_size_t end); > > +bool pat_pfn_is_uc_or_uc_minus(unsigned long pfn); > + > #endif /* _ASM_X86_PAT_H */ > diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c > index fe7d57a8fb60..e1282dd4eeb8 100644 > --- a/arch/x86/mm/pat.c > +++ b/arch/x86/mm/pat.c > @@ -677,6 +677,22 @@ static enum page_cache_mode lookup_memtype(u64 paddr) > return rettype; > } > > +/** > + * Check with PAT whether the memory type of a pfn is UC or UC-. > + * > + * Only to be called when PAT is enabled. > + * > + * Returns true, if the memory type of @pfn is UC or UC-. > + * Otherwise, returns false. > + */ > +bool pat_pfn_is_uc_or_uc_minus(unsigned long pfn) > +{ > + enum page_cache_mode cm = lookup_memtype(PFN_PHYS(pfn)); > + > + return cm == _PAGE_CACHE_MODE_UC || cm == _PAGE_CACHE_MODE_UC_MINUS; > +} > +EXPORT_SYMBOL_GPL(pat_pfn_is_uc_or_uc_minus); > + > /** > * io_reserve_memtype - Request a memory type mapping for a region of memory > * @start: start (physical address) of the region > Wonder if we should check for pat internally. And if we should simply return the memtype via lookup_memtype() instead of creating such a strange named function (by providing e.g. a lookup_memtype() variant that can be called with !pat_enabled()). The caller can easily check against _PAGE_CACHE_MODE_UC ... -- Thanks, David / dhildenb