linux-kernel - [PATCH AUTOSEL 4.14 05/12] s390/setup: avoid using memblock_enforce_memory

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Message-Id: <20211126023611.443098-5-sashal@kernel.org>
Date:   Thu, 25 Nov 2021 21:36:01 -0500
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Vasily Gorbik <gor@...ux.ibm.com>,
        Heiko Carstens <hca@...ux.ibm.com>,
        Sasha Levin <sashal@...nel.org>, borntraeger@...ux.ibm.com,
        agordeev@...ux.ibm.com, svens@...ux.ibm.com,
        egorenar@...ux.ibm.com, linux-s390@...r.kernel.org
Subject: [PATCH AUTOSEL 4.14 05/12] s390/setup: avoid using memblock_enforce_memory_limit

From: Vasily Gorbik <gor@...ux.ibm.com>

[ Upstream commit 5dbc4cb4667457b0c53bcd7bff11500b3c362975 ]

There is a difference in how architectures treat "mem=" option. For some
that is an amount of online memory, for s390 and x86 this is the limiting
max address. Some memblock api like memblock_enforce_memory_limit()
take limit argument and explicitly treat it as the size of online memory,
and use __find_max_addr to convert it to an actual max address. Current
s390 usage:

memblock_enforce_memory_limit(memblock_end_of_DRAM());

yields different results depending on presence of memory holes (offline
memory blocks in between online memory). If there are no memory holes
limit == max_addr in memblock_enforce_memory_limit() and it does trim
online memory and reserved memory regions. With memory holes present it
actually does nothing.

Since we already use memblock_remove() explicitly to trim online memory
regions to potential limit (think mem=, kdump, addressing limits, etc.)
drop the usage of memblock_enforce_memory_limit() altogether. Trimming
reserved regions should not be required, since we now use
memblock_set_current_limit() to limit allocations and any explicit memory
reservations above the limit is an actual problem we should not hide.

Reviewed-by: Heiko Carstens <hca@...ux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@...ux.ibm.com>
Signed-off-by: Heiko Carstens <hca@...ux.ibm.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 arch/s390/kernel/setup.c | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/arch/s390/kernel/setup.c b/arch/s390/kernel/setup.c
index ceaee215e2436..e9ef093eb6767 100644
--- a/arch/s390/kernel/setup.c
+++ b/arch/s390/kernel/setup.c
@@ -706,9 +706,6 @@ static void __init setup_memory(void)
 		storage_key_init_range(reg->base, reg->base + reg->size);
 	}
 	psw_set_key(PAGE_DEFAULT_KEY);
-
-	/* Only cosmetics */
-	memblock_enforce_memory_limit(memblock_end_of_DRAM());
 }

 /*
-- 
2.33.0