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Howlett , ryan.roberts@arm.com, Vlastimil Babka , lance.yang@linux.dev, linux-kernel@vger.kernel.org, nphamcs@gmail.com, shikemeng@huaweicloud.com, yosry@kernel.org, qi.zheng@linux.dev, luizcap@redhat.com, kernel-team@meta.com, Usama Arif , Alexander Gordeev , Gerald Schaefer , Heiko Carstens , Vasily Gorbik Subject: [PATCH v7 06/29] s390: mm: add PMD swap-exclusive helpers Date: Mon, 14 Sep 2026 04:41:58 -0700 Message-ID: <20260914114320.12988-7-usama.arif@linux.dev> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260914114320.12988-1-usama.arif@linux.dev> References: <20260914114320.12988-1-usama.arif@linux.dev> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: BFD6620003 X-Stat-Signature: 3gn3eiq34hxsir4hhf111xabpmopocmj X-Rspam-User: X-HE-Tag: 1789386238-606548 X-HE-Meta: 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 9uyeSehO uzhfrCeLJ9DuIp4I/ezYiR/dXQUfvnIeVYWxQvee+t0+duOwoEr6e9AGSpZKlWVsDJOpaG056UmKxplak+NRHjsYmmz9xYI+4knY+AGdR+vZQbmADWaQ2Tp11Cf/ORNMPDNV2hl2FJBUHdKXx70zbqAcqvbPcj7bO9RXlEEFEHW9No5Ie06Aumb53dxkBHll1wcvF1ArukeOybMIuJ3qCl8qrs/mjyKAAXXDnfymy/96KXkZdi/69Bbw7W/rgc5jWZrWT Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: A later patch keeps a PMD-mapped anonymous THP mapped by a PMD across the swap round-trip, so PG_anon_exclusive now has to survive in a swap PMD and not just in a swap PTE. s390 is the one architecture where a swap PMD is not a swap PTE in disguise: it is an RSTE with its own layout, converted to a fake PTE swap entry for the common code. Give it its own exclusive bit rather than borrowing the PTE-format macro. The two happen to have the same value, but that is a coincidence. Bit 52 was documented as unused; document what it is now. Cc: Alexander Gordeev Cc: Gerald Schaefer Cc: Heiko Carstens Cc: Vasily Gorbik Signed-off-by: Usama Arif --- arch/s390/include/asm/pgtable.h | 28 ++++++++++++++++++++++++++-- 1 file changed, 26 insertions(+), 2 deletions(-) diff --git a/arch/s390/include/asm/pgtable.h b/arch/s390/include/asm/pgtable.h index 2d5c2ab06de98..0790a0884cfab 100644 --- a/arch/s390/include/asm/pgtable.h +++ b/arch/s390/include/asm/pgtable.h @@ -333,6 +333,7 @@ void setup_protection_map(void); /* Common bits in region and segment table entries, for swap entries */ #define _RST_ENTRY_COMM 0x0010 /* Common-Region/Segment, marks swap entry */ #define _RST_ENTRY_INVALID 0x0020 /* invalid region/segment table entry */ +#define _RST_ENTRY_SWP_EXCLUSIVE 0x0800 /* SW exclusive swap bit, see mk_swap_rste() */ #define _CRST_ENTRIES 2048 /* number of region/segment table entries */ #define _PAGE_ENTRIES 256 /* number of page table entries */ @@ -859,6 +860,28 @@ static inline pte_t pte_swp_clear_exclusive(pte_t pte) return clear_pte_bit(pte, __pgprot(_PAGE_SWP_EXCLUSIVE)); } +#ifdef CONFIG_ARCH_HAS_PMD_SOFTLEAVES +/* + * A PMD swap entry is an RSTE, not a PTE, so it needs its own exclusive bit + * rather than the PTE-format _PAGE_SWP_EXCLUSIVE. The two happen to have the + * same value; see the RSTE swap layout above mk_swap_rste(). + */ +static inline pmd_t pmd_swp_mkexclusive(pmd_t pmd) +{ + return set_pmd_bit(pmd, __pgprot(_RST_ENTRY_SWP_EXCLUSIVE)); +} + +static inline bool pmd_swp_exclusive(pmd_t pmd) +{ + return pmd_val(pmd) & _RST_ENTRY_SWP_EXCLUSIVE; +} + +static inline pmd_t pmd_swp_clear_exclusive(pmd_t pmd) +{ + return clear_pmd_bit(pmd, __pgprot(_RST_ENTRY_SWP_EXCLUSIVE)); +} +#endif + static inline int pte_soft_dirty(pte_t pte) { return pte_val(pte) & _PAGE_SOFT_DIRTY; @@ -1900,15 +1923,16 @@ static inline swp_entry_t __swp_entry(unsigned long type, unsigned long offset) * Bits 59 and 63 are used to indicate the swap entry. Bit 58 marks the rste * as invalid. * A swap entry is indicated by bit pattern (rste & 0x011) == 0x010 - * | offset |Xtype |11TT|S0| + * | offset |Etype |11TT|S0| * |0000000000111111111122222222223333333333444444444455|555555|5566|66| * |0123456789012345678901234567890123456789012345678901|234567|8901|23| * * Bits 0-51 store the offset. + * Bit 52 (E) is used to remember PG_anon_exclusive + * (_RST_ENTRY_SWP_EXCLUSIVE), mirroring bit 52 of a swap pte. * Bits 53-57 store the type. * Bit 62 (S) is used for softdirty tracking. * Bits 60-61 (TT) indicate the table type: 0x01 for REGION3 and 0x00 for SEGMENT. - * Bit 52 (X) is unused. */ #define __SWP_OFFSET_MASK_RSTE ((1UL << 52) - 1) -- 2.53.0-Meta