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Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.4.0 MIME-Version: 1.0 In-Reply-To: <02b9ec67-75c5-4a36-9110-cc4ba6ee4f94@arm.com> Content-Language: en-US X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190228_110020_124845_5A9ED20E X-CRM114-Status: GOOD ( 18.15 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Mark Rutland , Dave Hansen , Arnd Bergmann , Ard Biesheuvel , Peter Zijlstra , Catalin Marinas , x86@kernel.org, Will Deacon , linux-kernel@vger.kernel.org, =?UTF-8?B?SsOpcsO0bWUgR2xpc3Nl?= , Ingo Molnar , Borislav Petkov , Andy Lutomirski , "H. Peter Anvin" , James Morse , Thomas Gleixner , linux-arm-kernel@lists.infradead.org, "Liang, Kan" Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 2/28/19 3:28 AM, Steven Price wrote: > static int get_level(unsigned long addr, unsigned long end) > { > /* Add 1 to account for ~0ULL */ > unsigned long size = (end - addr) + 1; > if (size < PMD_SIZE) > return 4; > else if (size < PUD_SIZE) > return 3; > else if (size < P4D_SIZE) > return 2; > else if (size < PGD_SIZE) > return 1; > return 0; > } > > There are two immediate problems with that: > > * The "+1" to deal with ~0ULL is fragile > > * PGD_SIZE isn't what you might expect, it's not defined for most > architectures and arm64/x86 use it as the size of the PGD table. > Although that's easy enough to fix up. > > Do you think a function like above would be preferable? The question still stands of why we *need* the depth/level in the first place. As I said, we obviously need it for printing out the "name" of the level. Is that it? > The other option would of course be to just drop the information from > the debugfs file about at which level the holes are. But it can be > useful information to see whether there are empty levels in the page > table structure. Although this is an area where x86 and arm64 differ > currently (x86 explicitly shows the gaps, arm64 doesn't), so if x86 > doesn't mind losing that functionality that would certainly simplify things! I think I'd actually be OK with the holes just not showing up. I actually find it kinda hard to read sometimes with the holes in there. I'd be curious what others think though. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel