linux-kernel - Re: [PATCH AUTOSEL 5.15 081/188] s390/nmi: add missing __pa/__va address conversion of extended save area

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Message-ID: <aef11e2f-2b92-e713-a407-3bebf9b3340d@linux.ibm.com>
Date:   Tue, 18 Jan 2022 09:18:40 +0100
From:   Christian Borntraeger <borntraeger@...ux.ibm.com>
To:     Sasha Levin <sashal@...nel.org>, linux-kernel@...r.kernel.org,
        stable@...r.kernel.org
Cc:     Heiko Carstens <hca@...ux.ibm.com>,
        Vineeth Vijayan <vneethv@...ux.ibm.com>, gor@...ux.ibm.com,
        egorenar@...ux.ibm.com, agordeev@...ux.ibm.com,
        svens@...ux.ibm.com, ebiederm@...ssion.com,
        valentin.schneider@....com, rppt@...nel.org, iii@...ux.ibm.com,
        linux-s390@...r.kernel.org
Subject: Re: [PATCH AUTOSEL 5.15 081/188] s390/nmi: add missing __pa/__va
 address conversion of extended save area

Am 18.01.22 um 03:30 schrieb Sasha Levin:
> From: Heiko Carstens <hca@...ux.ibm.com>
> 
> [ Upstream commit 402ff5a3387dc8ec6987a80d3ce26b0c25773622 ]
> 
> Add missing __pa/__va address conversion of machine check extended
> save area designation, which is an absolute address.
> 

vv
> Note: this currently doesn't fix a real bug, since virtual addresses
> are indentical to physical ones.
^^

Sasha,
please note the disclaimer above. There will be plenty of such fixes
in s390 code and there is no point in backporting single fixes to stable.
It will provide no benefit on its own but adds a risk of regression.



> 
> Reported-by: Vineeth Vijayan <vneethv@...ux.ibm.com>
> Tested-by: Vineeth Vijayan <vneethv@...ux.ibm.com>
> Signed-off-by: Heiko Carstens <hca@...ux.ibm.com>
> Signed-off-by: Sasha Levin <sashal@...nel.org>
> ---
>   arch/s390/kernel/machine_kexec.c |  2 +-
>   arch/s390/kernel/nmi.c           | 10 +++++-----
>   arch/s390/kernel/smp.c           |  2 +-
>   3 files changed, 7 insertions(+), 7 deletions(-)
> 
> diff --git a/arch/s390/kernel/machine_kexec.c b/arch/s390/kernel/machine_kexec.c
> index 0505e55a62979..a16467b3825ec 100644
> --- a/arch/s390/kernel/machine_kexec.c
> +++ b/arch/s390/kernel/machine_kexec.c
> @@ -86,7 +86,7 @@ static noinline void __machine_kdump(void *image)
>   			continue;
>   	}
>   	/* Store status of the boot CPU */
> -	mcesa = (struct mcesa *)(S390_lowcore.mcesad & MCESA_ORIGIN_MASK);
> +	mcesa = __va(S390_lowcore.mcesad & MCESA_ORIGIN_MASK);
>   	if (MACHINE_HAS_VX)
>   		save_vx_regs((__vector128 *) mcesa->vector_save_area);
>   	if (MACHINE_HAS_GS) {
> diff --git a/arch/s390/kernel/nmi.c b/arch/s390/kernel/nmi.c
> index 20f8e1868853f..3f18c1412eba3 100644
> --- a/arch/s390/kernel/nmi.c
> +++ b/arch/s390/kernel/nmi.c
> @@ -68,7 +68,7 @@ void __init nmi_alloc_boot_cpu(struct lowcore *lc)
>   {
>   	if (!nmi_needs_mcesa())
>   		return;
> -	lc->mcesad = (unsigned long) &boot_mcesa;
> +	lc->mcesad = __pa(&boot_mcesa);
>   	if (MACHINE_HAS_GS)
>   		lc->mcesad |= ilog2(MCESA_MAX_SIZE);
>   }
> @@ -94,7 +94,7 @@ static int __init nmi_init(void)
>   	__ctl_store(cr0, 0, 0);
>   	__ctl_clear_bit(0, 28); /* disable lowcore protection */
>   	/* Replace boot_mcesa on the boot CPU */
> -	S390_lowcore.mcesad = origin | mcesa_origin_lc;
> +	S390_lowcore.mcesad = __pa(origin) | mcesa_origin_lc;
>   	__ctl_load(cr0, 0, 0);
>   	return 0;
>   }
> @@ -111,7 +111,7 @@ int nmi_alloc_per_cpu(struct lowcore *lc)
>   		return -ENOMEM;
>   	/* The pointer is stored with mcesa_bits ORed in */
>   	kmemleak_not_leak((void *) origin);
> -	lc->mcesad = origin | mcesa_origin_lc;
> +	lc->mcesad = __pa(origin) | mcesa_origin_lc;
>   	return 0;
>   }
>   
> @@ -119,7 +119,7 @@ void nmi_free_per_cpu(struct lowcore *lc)
>   {
>   	if (!nmi_needs_mcesa())
>   		return;
> -	kmem_cache_free(mcesa_cache, (void *)(lc->mcesad & MCESA_ORIGIN_MASK));
> +	kmem_cache_free(mcesa_cache, __va(lc->mcesad & MCESA_ORIGIN_MASK));
>   }
>   
>   static notrace void s390_handle_damage(void)
> @@ -246,7 +246,7 @@ static int notrace s390_validate_registers(union mci mci, int umode)
>   			: "Q" (S390_lowcore.fpt_creg_save_area));
>   	}
>   
> -	mcesa = (struct mcesa *)(S390_lowcore.mcesad & MCESA_ORIGIN_MASK);
> +	mcesa = __va(S390_lowcore.mcesad & MCESA_ORIGIN_MASK);
>   	if (!MACHINE_HAS_VX) {
>   		/* Validate floating point registers */
>   		asm volatile(
> diff --git a/arch/s390/kernel/smp.c b/arch/s390/kernel/smp.c
> index 1a04e5bdf6555..5c3d3d8f6b5d8 100644
> --- a/arch/s390/kernel/smp.c
> +++ b/arch/s390/kernel/smp.c
> @@ -622,7 +622,7 @@ int smp_store_status(int cpu)
>   		return -EIO;
>   	if (!MACHINE_HAS_VX && !MACHINE_HAS_GS)
>   		return 0;
> -	pa = __pa(lc->mcesad & MCESA_ORIGIN_MASK);
> +	pa = lc->mcesad & MCESA_ORIGIN_MASK;
>   	if (MACHINE_HAS_GS)
>   		pa |= lc->mcesad & MCESA_LC_MASK;
>   	if (__pcpu_sigp_relax(pcpu->address, SIGP_STORE_ADDITIONAL_STATUS,