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Tue, 21 Jul 2026 09:59:12 +0000 (GMT) Received: from tuxmaker.linux.ibm.com (unknown [9.87.85.9]) by smtpav04.fra02v.mail.ibm.com (Postfix) with ESMTPS; Tue, 21 Jul 2026 09:59:12 +0000 (GMT) From: Sven Schnelle To: Heiko Carstens Cc: Alexander Gordeev , Vasily Gorbik , Christian Borntraeger , Janosch Frank , Claudio Imbrenda , David Hildenbrand , linux-s390@vger.kernel.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v4 8/8] s390: Add support for DCACHE_WORD_ACCESS (again) In-Reply-To: <20260720085834.898025-9-hca@linux.ibm.com> References: <20260720085834.898025-1-hca@linux.ibm.com> <20260720085834.898025-9-hca@linux.ibm.com> Date: Tue, 21 Jul 2026 11:59:11 +0200 Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: Qbi-E-chf0pfWLaaoAu0uV_ESZqdnXJu X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNzIxMDEwMiBTYWx0ZWRfX1MSl8ZdxC3hK CwZ+NYtPer3bRebvDaC8ygVq4MBdqoIMUgqyMVOulI/wMYWP0TaKvyM8aAi+gGf2RIIqAvSCiSi niPk5QBgOzUPSHqdI6Bvz0E/RsRxSxDypgSYY/mPvBjnQBRB2ipiFpwgPsEZv8SZ8H3FBgW5SrV zP5dBwbbh8opRwcOUtfr+B3q2A/rKnzOqUy+JV8kg22dnFFS6rx+IRAqBwKyaMv1KOCMLY8gjrf rt8U51XtK6ao+5ADS9xPwJs+KfqvpZ7kb3zTd9xrOvedVLSjg8/uUvmtB0WYWuVIIaKnquC+PM3 oHVbzEE1jVXbwLwlyEpfi54qcU/utdTxTuNn5tgJxkJAc2HGlyn348borcbagFu7t7HI5pkpX6x 1KCKIc1qfyDnjYiGpRxFo8L3/gc9aIYX7peTuCnsOqaXVCUyMVfk1pd8IJ7WtNxvb0Boz6AHvmO FP6ATsdfWF0ehz7Zj1w== X-Proofpoint-Spam-Info: AW1haW4tMjYwNzIxMDEwMiBTYWx0ZWRfX3t+y3n0BBUdd 1Day50jduvLUU7dgCPRYUSVYP4D2hHnTueZnbaipOKi3YqKTZdjkL8pRUWDWwXZ9E7mi33zFGYP 7ocyLkoCOF2O/b30O5MH4c8w/h3mr6k= X-Proofpoint-GUID: Qbi-E-chf0pfWLaaoAu0uV_ESZqdnXJu X-Authority-Analysis: v=2.4 cv=SM5ykuvH c=1 sm=1 tr=0 ts=6a5f42f5 cx=c_pps a=3Bg1Hr4SwmMryq2xdFQyZA==:117 a=3Bg1Hr4SwmMryq2xdFQyZA==:17 a=RAioF0-LDSMA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=RzCfie-kr_QcCd8fBx8p:22 a=VnNF1IyMAAAA:8 a=VAyOQAVIeXdyq_GhAlYA:9 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.134,FMLib:17.12.100.49 definitions=2026-07-20_06,2026-07-20_03,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 clxscore=1011 lowpriorityscore=0 bulkscore=0 suspectscore=0 adultscore=0 spamscore=0 malwarescore=0 priorityscore=1501 phishscore=0 impostorscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2607210102 Heiko Carstens writes: > Implement load_unaligned_zeropad() and enable DCACHE_WORD_ACCESS to > speed up string operations in fs/dcache.c and fs/namei.c. > > With the secure storage access exception cases addressed, add support > for DCACHE_WORD_ACCESS again. > > Tested-by: Christian Borntraeger > Signed-off-by: Heiko Carstens > --- > arch/s390/Kconfig | 1 + > arch/s390/include/asm/asm-extable.h | 4 ++++ > arch/s390/include/asm/word-at-a-time.h | 22 ++++++++++++++++++++++ > arch/s390/mm/extable.c | 18 ++++++++++++++++++ > 4 files changed, 45 insertions(+) > > diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig > index 84404e6778d5..fe81c539ef2f 100644 > --- a/arch/s390/Kconfig > +++ b/arch/s390/Kconfig > @@ -163,6 +163,7 @@ config S390 > select ARCH_WANTS_THP_SWAP > select BUILDTIME_TABLE_SORT > select CLONE_BACKWARDS2 > + select DCACHE_WORD_ACCESS if !KMSAN > select DYNAMIC_FTRACE if FUNCTION_TRACER > select FUNCTION_ALIGNMENT_8B if CC_IS_GCC > select FUNCTION_ALIGNMENT_16B if !CC_IS_GCC > diff --git a/arch/s390/include/asm/asm-extable.h b/arch/s390/include/asm/asm-extable.h > index 99748c20e767..d23ea0c94e4e 100644 > --- a/arch/s390/include/asm/asm-extable.h > +++ b/arch/s390/include/asm/asm-extable.h > @@ -12,6 +12,7 @@ > #define EX_TYPE_UA_FAULT 3 > #define EX_TYPE_UA_LOAD_REG 5 > #define EX_TYPE_UA_LOAD_REGPAIR 6 > +#define EX_TYPE_ZEROPAD 7 > #define EX_TYPE_FPC 8 > #define EX_TYPE_UA_MVCOS_TO 9 > #define EX_TYPE_UA_MVCOS_FROM 10 > @@ -79,6 +80,9 @@ > #define EX_TABLE_UA_LOAD_REGPAIR(_fault, _target, _regerr, _regzero) \ > __EX_TABLE(__ex_table, _fault, _target, EX_TYPE_UA_LOAD_REGPAIR, _regerr, _regzero, 0) > > +#define EX_TABLE_ZEROPAD(_fault, _target, _regdata, _regaddr) \ > + __EX_TABLE(__ex_table, _fault, _target, EX_TYPE_ZEROPAD, _regdata, _regaddr, 0) > + > #define EX_TABLE_FPC(_fault, _target) \ > __EX_TABLE(__ex_table, _fault, _target, EX_TYPE_FPC, __stringify(%%r0), __stringify(%%r0), 0) > > diff --git a/arch/s390/include/asm/word-at-a-time.h b/arch/s390/include/asm/word-at-a-time.h > index e9287036392d..eaa19dee7699 100644 > --- a/arch/s390/include/asm/word-at-a-time.h > +++ b/arch/s390/include/asm/word-at-a-time.h > @@ -4,6 +4,7 @@ > > #include > #include > +#include > #include > > struct word_at_a_time { > @@ -40,4 +41,25 @@ static inline unsigned long zero_bytemask(unsigned long data) > return ~1UL << data; > } > > +/* > + * Load an unaligned word from kernel space. > + * > + * In the (very unlikely) case of the word being a page-crosser > + * and the next page not being mapped, take the exception and > + * return zeroes in the non-existing part. > + */ > +static inline unsigned long load_unaligned_zeropad(const void *addr) > +{ > + unsigned long data; > + > + asm_inline volatile( > + "0: lg %[data],0(%[addr])\n" > + "1: nopr %%r7\n" > + EX_TABLE_ZEROPAD(0b, 1b, %[data], %[addr]) > + EX_TABLE_ZEROPAD(1b, 1b, %[data], %[addr]) > + : [data] "=d" (data) > + : [addr] "a" (addr), "m" (*(unsigned long *)addr)); > + return data; > +} > + > #endif /* _ASM_WORD_AT_A_TIME_H */ > diff --git a/arch/s390/mm/extable.c b/arch/s390/mm/extable.c > index 063b4346742d..7498e858c401 100644 > --- a/arch/s390/mm/extable.c > +++ b/arch/s390/mm/extable.c > @@ -50,6 +50,22 @@ static bool ex_handler_ua_load_reg(const struct exception_table_entry *ex, > return true; > } > > +static bool ex_handler_zeropad(const struct exception_table_entry *ex, struct pt_regs *regs) > +{ > + unsigned int reg_addr = FIELD_GET(EX_DATA_REG_ADDR, ex->data); > + unsigned int reg_data = FIELD_GET(EX_DATA_REG_ERR, ex->data); > + unsigned long data, addr, offset; > + > + addr = regs->gprs[reg_addr]; > + offset = addr & (sizeof(unsigned long) - 1); > + addr &= ~(sizeof(unsigned long) - 1); > + data = *(unsigned long *)addr; > + data <<= BITS_PER_BYTE * offset; > + regs->gprs[reg_data] = data; > + regs->psw.addr = extable_fixup(ex); > + return true; > +} > + > static bool ex_handler_fpc(const struct exception_table_entry *ex, struct pt_regs *regs) > { > fpu_sfpc(0); > @@ -118,6 +134,8 @@ bool fixup_exception(struct pt_regs *regs) > return ex_handler_ua_load_reg(ex, false, regs); > case EX_TYPE_UA_LOAD_REGPAIR: > return ex_handler_ua_load_reg(ex, true, regs); > + case EX_TYPE_ZEROPAD: > + return ex_handler_zeropad(ex, regs); > case EX_TYPE_FPC: > return ex_handler_fpc(ex, regs); > case EX_TYPE_UA_MVCOS_TO: Reviewed-by: Sven Schnelle