Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756172AbcC2Iz4 (ORCPT ); Tue, 29 Mar 2016 04:55:56 -0400 Received: from mailapp01.imgtec.com ([195.59.15.196]:57097 "EHLO mailapp01.imgtec.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751136AbcC2Izx (ORCPT ); Tue, 29 Mar 2016 04:55:53 -0400 Date: Tue, 29 Mar 2016 09:55:49 +0100 From: Paul Burton To: Ralf Baechle CC: , Lars Persson , , Andrew Morton , "Kirill A. Shutemov" Subject: Re: [PATCH 2/4] MIPS: Flush highmem pages in __flush_dcache_page Message-ID: <20160329085549.GA17987@NP-P-BURTON> References: <1456799879-14711-1-git-send-email-paul.burton@imgtec.com> <1456799879-14711-3-git-send-email-paul.burton@imgtec.com> <20160329083543.GD11282@linux-mips.org> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Disposition: inline In-Reply-To: <20160329083543.GD11282@linux-mips.org> User-Agent: Mutt/1.5.23 (2014-03-12) X-Originating-IP: [10.100.200.97] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2893 Lines: 78 On Tue, Mar 29, 2016 at 10:35:43AM +0200, Ralf Baechle wrote: > On Tue, Mar 01, 2016 at 02:37:57AM +0000, Paul Burton wrote: > > > When flush_dcache_page is called on an executable page, that page is > > about to be provided to userland & we can presume that the icache > > contains no valid entries for its address range. However if the icache > > does not fill from the dcache then we cannot presume that the pages > > content has been written back as far as the memories that the dcache > > will fill from (ie. L2 or further out). > > > > This was being done for lowmem pages, but not for highmem which can lead > > to icache corruption. Fix this by mapping highmem pages & flushing their > > content from the dcache in __flush_dcache_page before providing the page > > to userland, just as is done for lowmem pages. > > > > Signed-off-by: Paul Burton > > Cc: Lars Persson > > --- > > > > arch/mips/mm/cache.c | 12 +++++++++--- > > 1 file changed, 9 insertions(+), 3 deletions(-) > > > > diff --git a/arch/mips/mm/cache.c b/arch/mips/mm/cache.c > > index 3f159ca..5a67d8c 100644 > > --- a/arch/mips/mm/cache.c > > +++ b/arch/mips/mm/cache.c > > @@ -16,6 +16,7 @@ > > #include > > > > #include > > +#include > > #include > > #include > > #include > > @@ -83,8 +84,6 @@ void __flush_dcache_page(struct page *page) > > struct address_space *mapping = page_mapping(page); > > unsigned long addr; > > > > - if (PageHighMem(page)) > > - return; > > if (mapping && !mapping_mapped(mapping)) { > > SetPageDcacheDirty(page); > > return; > > @@ -95,8 +94,15 @@ void __flush_dcache_page(struct page *page) > > * case is for exec env/arg pages and those are %99 certainly going to > > * get faulted into the tlb (and thus flushed) anyways. > > */ > > - addr = (unsigned long) page_address(page); > > + if (PageHighMem(page)) > > + addr = (unsigned long)kmap_atomic(page); > > + else > > + addr = (unsigned long)page_address(page); > > + > > flush_data_cache_page(addr); > > + > > + if (PageHighMem(page)) > > + __kunmap_atomic((void *)addr); > > } > > > > EXPORT_SYMBOL(__flush_dcache_page); > > I don't see how this should work with cache aliases. If the page is unmapped > kmap_atomic will pick a deterministic address only under some circumstances, > kmap won't. As the result the wrong cache way will be flushed out, I think. > > Ralf Hi Ralf, None of the systems I tested this on have cache aliases, and highmem on systems with cache aliases is currently unsupported to the extent that we BUG_ON such cases in flush_kernel_dcache_page. So hopefully you won't require that this code making highmem without aliases also fix the currently-unsupported highmem with aliases case? Thanks, Paul