From 37540b8c287fc817bdbd0c62bb75ad6eab0e5d03 Mon Sep 17 00:00:00 2001 From: Heiko Carstens Date: Thu, 11 Jun 2026 17:37:46 +0200 Subject: [PATCH] s390: Revert support for DCACHE_WORD_ACCESS load_unaligned_zeropad() reads eight bytes from unaligned addresses and may cross page boundaries. It handles exceptions which may happen if reading from the second page results in an exception. For pages which are donated to the Ultravisor for secure execution purposes the do_secure_storage_access() exception handler however does not handle such exceptions correctly. Such an exception may result in an endless exception loop which will never be resolved. An attempt to fix this [1] turned out to be not sufficient. For now revert load_unaligned_zeropad() until this problem has been resolved in a proper way. Note that the implementation of load_unaligned_zeropad() itself is correct. The revert is just a temporary workaround until there is complete fix for secure storage access exceptions. [1] commit b00be77302d7 ("s390/mm: Add missing secure storage access fixups for donated memory") Fixes: 802ba53eefc5 ("s390: add support for DCACHE_WORD_ACCESS") Cc: stable@vger.kernel.org Acked-by: Christian Borntraeger Signed-off-by: Heiko Carstens Signed-off-by: Alexander Gordeev --- 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 deletions(-) diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig index fe5eebaecb7c..33988cc96af1 100644 --- a/arch/s390/Kconfig +++ b/arch/s390/Kconfig @@ -166,7 +166,6 @@ 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 d23ea0c94e4e..99748c20e767 100644 --- a/arch/s390/include/asm/asm-extable.h +++ b/arch/s390/include/asm/asm-extable.h @@ -12,7 +12,6 @@ #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 @@ -80,9 +79,6 @@ #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 eaa19dee7699..e9287036392d 100644 --- a/arch/s390/include/asm/word-at-a-time.h +++ b/arch/s390/include/asm/word-at-a-time.h @@ -4,7 +4,6 @@ #include #include -#include #include struct word_at_a_time { @@ -41,25 +40,4 @@ 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 7498e858c401..063b4346742d 100644 --- a/arch/s390/mm/extable.c +++ b/arch/s390/mm/extable.c @@ -50,22 +50,6 @@ 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); @@ -134,8 +118,6 @@ 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: