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    Subject[PATCH 5.19 1004/1157] s390/smp: enforce lowcore protection on CPU restart
    Date
    From: Alexander Gordeev <agordeev@linux.ibm.com>

    [ Upstream commit 6f5c672d17f583b081e283927f5040f726c54598 ]

    As result of commit 915fea04f932 ("s390/smp: enable DAT before
    CPU restart callback is called") the low-address protection bit
    gets mistakenly unset in control register 0 save area of the
    absolute zero memory. That area is used when manual PSW restart
    happened to hit an offline CPU. In this case the low-address
    protection for that CPU will be dropped.

    Reviewed-by: Heiko Carstens <hca@linux.ibm.com>
    Fixes: 915fea04f932 ("s390/smp: enable DAT before CPU restart callback is called")
    Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    arch/s390/kernel/setup.c | 2 +-
    1 file changed, 1 insertion(+), 1 deletion(-)

    diff --git a/arch/s390/kernel/setup.c b/arch/s390/kernel/setup.c
    index 0a37f5de2863..1ead1293ba17 100644
    --- a/arch/s390/kernel/setup.c
    +++ b/arch/s390/kernel/setup.c
    @@ -508,8 +508,8 @@ static void __init setup_lowcore_dat_on(void)
    S390_lowcore.svc_new_psw.mask |= PSW_MASK_DAT;
    S390_lowcore.program_new_psw.mask |= PSW_MASK_DAT;
    S390_lowcore.io_new_psw.mask |= PSW_MASK_DAT;
    - __ctl_store(S390_lowcore.cregs_save_area, 0, 15);
    __ctl_set_bit(0, 28);
    + __ctl_store(S390_lowcore.cregs_save_area, 0, 15);
    put_abs_lowcore(restart_flags, RESTART_FLAG_CTLREGS);
    put_abs_lowcore(program_new_psw, lc->program_new_psw);
    for (cr = 0; cr < ARRAY_SIZE(lc->cregs_save_area); cr++)
    --
    2.35.1


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