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Tue, 23 Jun 2020 07:30:32 +0000 Received: from b06wcsmtp001.portsmouth.uk.ibm.com (b06wcsmtp001.portsmouth.uk.ibm.com [9.149.105.160]) by b06cxnps3074.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 05N7UTcL655790 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 23 Jun 2020 07:30:29 GMT Received: from b06wcsmtp001.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 3654EA405C; Tue, 23 Jun 2020 07:30:29 +0000 (GMT) Received: from b06wcsmtp001.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id EFD0EA4054; Tue, 23 Jun 2020 07:30:25 +0000 (GMT) Received: from bharata.ibmuc.com (unknown [9.199.54.229]) by b06wcsmtp001.portsmouth.uk.ibm.com (Postfix) with ESMTP; Tue, 23 Jun 2020 07:30:25 +0000 (GMT) From: Bharata B Rao To: linuxppc-dev@lists.ozlabs.org Subject: [PATCH v1 1/3] powerpc/mm/radix: Create separate mappings for hot-plugged memory Date: Tue, 23 Jun 2020 13:00:15 +0530 Message-Id: <20200623073017.1951-2-bharata@linux.ibm.com> X-Mailer: git-send-email 2.21.3 In-Reply-To: <20200623073017.1951-1-bharata@linux.ibm.com> References: <20200623073017.1951-1-bharata@linux.ibm.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.216, 18.0.687 definitions=2020-06-23_04:2020-06-22, 2020-06-23 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 mlxlogscore=999 malwarescore=0 suspectscore=1 adultscore=0 impostorscore=0 mlxscore=0 spamscore=0 clxscore=1015 cotscore=-2147483648 phishscore=0 bulkscore=0 lowpriorityscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2004280000 definitions=main-2006230054 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: aneesh.kumar@linux.ibm.com, Bharata B Rao , npiggin@gmail.com Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" Memory that gets hot-plugged _during_ boot (and not the memory that gets plugged in after boot), is mapped with 1G mappings and will undergo splitting when it is unplugged. The splitting code has a few issues: 1. Recursive locking -------------------- Memory unplug path takes cpu_hotplug_lock and calls stop_machine() for splitting the mappings. However stop_machine() takes cpu_hotplug_lock again causing deadlock. 2. BUG: sleeping function called from in_atomic() context --------------------------------------------------------- Memory unplug path (remove_pagetable) takes init_mm.page_table_lock spinlock and later calls stop_machine() which does wait_for_completion() 3. Bad unlock unbalance ----------------------- Memory unplug path takes init_mm.page_table_lock spinlock and calls stop_machine(). The stop_machine thread function runs in a different thread context (migration thread) which tries to release and reaquire ptl. Releasing ptl from a different thread than which acquired it causes bad unlock unbalance. These problems can be avoided if we avoid mapping hot-plugged memory with 1G mapping, thereby removing the need for splitting them during unplug. Hence, during radix init, identify the hot-plugged memory region and create separate mappings for each LMB so that they don't get mapped with 1G mappings. The identification of hot-plugged memory has become possible after the commit b6eca183e23e ("powerpc/kernel: Enables memory hot-remove after reboot on pseries guests"). To create separate mappings for every LMB in the hot-plugged region, we need lmb-size for which we use memory_block_size_bytes(). Since this is early init time code, the machine type isn't probed yet and hence memory_block_size_bytes() would return the default LMB size as 16MB. Hence we end up issuing more number of mapping requests than earlier. Signed-off-by: Bharata B Rao --- arch/powerpc/mm/book3s64/radix_pgtable.c | 15 ++++++++++++--- 1 file changed, 12 insertions(+), 3 deletions(-) diff --git a/arch/powerpc/mm/book3s64/radix_pgtable.c b/arch/powerpc/mm/book3s64/radix_pgtable.c index 8acb96de0e48..ffccfe00ca2a 100644 --- a/arch/powerpc/mm/book3s64/radix_pgtable.c +++ b/arch/powerpc/mm/book3s64/radix_pgtable.c @@ -16,6 +16,7 @@ #include #include #include +#include #include #include @@ -320,6 +321,8 @@ static void __init radix_init_pgtable(void) { unsigned long rts_field; struct memblock_region *reg; + phys_addr_t addr; + u64 lmb_size = memory_block_size_bytes(); /* We don't support slb for radix */ mmu_slb_size = 0; @@ -338,9 +341,15 @@ static void __init radix_init_pgtable(void) continue; } - WARN_ON(create_physical_mapping(reg->base, - reg->base + reg->size, - -1, PAGE_KERNEL)); + if (memblock_is_hotpluggable(reg)) { + for (addr = reg->base; addr < (reg->base + reg->size); + addr += lmb_size) + WARN_ON(create_physical_mapping(addr, + addr + lmb_size, -1, PAGE_KERNEL)); + } else + WARN_ON(create_physical_mapping(reg->base, + reg->base + reg->size, + -1, PAGE_KERNEL)); } /* Find out how many PID bits are supported */ -- 2.21.3