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Tue, 29 Mar 2022 16:48:31 +0000 (UTC) Received: from t480s.redhat.com (unknown [10.39.194.134]) by smtp.corp.redhat.com (Postfix) with ESMTP id AA9B01121330; Tue, 29 Mar 2022 16:47:33 +0000 (UTC) From: David Hildenbrand To: linux-kernel@vger.kernel.org Subject: [PATCH v2 5/8] s390/pgtable: cleanup description of swp pte layout Date: Tue, 29 Mar 2022 18:43:26 +0200 Message-Id: <20220329164329.208407-6-david@redhat.com> In-Reply-To: <20220329164329.208407-1-david@redhat.com> References: <20220329164329.208407-1-david@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 2.78 on 10.11.54.3 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: x86@kernel.org, Jan Kara , David Hildenbrand , Catalin Marinas , Yang Shi , Dave Hansen , Peter Xu , Michal Hocko , linux-mm@kvack.org, Donald Dutile , Liang Zhang , Borislav Petkov , Alexander Gordeev , Will Deacon , Christoph Hellwig , Paul Mackerras , Andrea Arcangeli , linux-s390@vger.kernel.org, Vasily Gorbik , Rik van Riel , Hugh Dickins , Matthew Wilcox , Mike Rapoport , Ingo Molnar , linux-arm-kernel@lists.infradead.org, Jason Gunthorpe , David Rientjes , Gerald Schaefer , Pedro Gomes , Jann Horn , John Hubbard , Heiko Carstens , Shakeel Butt , Thomas Gleixner , Vlastimil Babka , Oded Gabbay , linuxppc-dev@lists.ozlabs.org, Oleg Nesterov , Nadav Amit , Andrew Morton , Linus Torvalds , Roman Gushchin , "Kirill A . Shutemov" , Mike Kravetz Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" Bit 52 and bit 55 don't have to be zero: they only trigger a translation-specifiation exception if the PTE is marked as valid, which is not the case for swap ptes. Document which bits are used for what, and which ones are unused. Signed-off-by: David Hildenbrand --- arch/s390/include/asm/pgtable.h | 17 ++++++++--------- 1 file changed, 8 insertions(+), 9 deletions(-) diff --git a/arch/s390/include/asm/pgtable.h b/arch/s390/include/asm/pgtable.h index 9df679152620..3982575bb586 100644 --- a/arch/s390/include/asm/pgtable.h +++ b/arch/s390/include/asm/pgtable.h @@ -1712,18 +1712,17 @@ static inline int has_transparent_hugepage(void) /* * 64 bit swap entry format: * A page-table entry has some bits we have to treat in a special way. - * Bits 52 and bit 55 have to be zero, otherwise a specification - * exception will occur instead of a page translation exception. The - * specification exception has the bad habit not to store necessary - * information in the lowcore. - * Bits 54 and 63 are used to indicate the page type. + * Bits 54 and 63 are used to indicate the page type. Bit 53 marks the pte + * as invalid. * A swap pte is indicated by bit pattern (pte & 0x201) == 0x200 - * This leaves the bits 0-51 and bits 56-62 to store type and offset. - * We use the 5 bits from 57-61 for the type and the 52 bits from 0-51 - * for the offset. - * | offset |01100|type |00| + * | offset |X11XX|type |S0| * |0000000000111111111122222222223333333333444444444455|55555|55566|66| * |0123456789012345678901234567890123456789012345678901|23456|78901|23| + * + * Bits 0-51 store the offset. + * Bits 57-61 store the type. + * Bit 62 (S) is used for softdirty tracking. + * Bits 52, 55 and 56 (X) are unused. */ #define __SWP_OFFSET_MASK ((1UL << 52) - 1) -- 2.35.1