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Wed, 21 Aug 2019 10:30:14 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 23ED2306B81; Wed, 21 Aug 2019 12:29:39 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id BA91920A21FC4; Wed, 21 Aug 2019 12:30:10 +0200 (CEST) Date: Wed, 21 Aug 2019 12:30:10 +0200 From: Peter Zijlstra To: Song Liu Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, kernel-team@fb.com, stable@vger.kernel.org, Joerg Roedel , Thomas Gleixner , Dave Hansen , Andy Lutomirski Subject: Re: [PATCH v2] x86/mm/pti: in pti_clone_pgtable(), increase addr properly Message-ID: <20190821103010.GJ2386@hirez.programming.kicks-ass.net> References: <20190820202314.1083149-1-songliubraving@fb.com> <20190821101008.GX2349@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190821101008.GX2349@hirez.programming.kicks-ass.net> User-Agent: Mutt/1.10.1 (2018-07-13) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed, Aug 21, 2019 at 12:10:08PM +0200, Peter Zijlstra wrote: > On Tue, Aug 20, 2019 at 01:23:14PM -0700, Song Liu wrote: > > host-5.2-after # grep "x pmd" /sys/kernel/debug/page_tables/dump_pid > > 0x0000000000600000-0x0000000000e00000 8M USR ro PSE x pmd > > 0xffffffff81000000-0xffffffff81e00000 14M ro PSE GLB x pmd > > > > So after this patch, the 5.2 based kernel has 7 PMDs instead of 1 PMD > > in 4.16 kernel. > > This basically gives rise to more questions than it provides answers. > You seem to have 'forgotten' to provide the equivalent mappings on the > two older kernels. The fact that they're not PMD is evident, but it > would be very good to know what is mapped, and what -- if anything -- > lives in the holes we've (accidentally) created. > > Can you please provide more complete mappings? Basically provide the > whole cpu_entry_area mapping. I tried on my local machine and: cat /debug/page_tables/kernel | awk '/^---/ { p=0 } /CPU entry/ { p=1 } { if (p) print $0 }' > ~/cea-{before,after}.txt resulted in _identical_ files ?!?! Can you share your before and after dumps?