From: Volodymyr Babchuk <Volodymyr_Babchuk@epam.com>
To: Stefano Stabellini <sstabellini@kernel.org>
Cc: "xen-devel@lists.xenproject.org" <xen-devel@lists.xenproject.org>,
"julien.grall@arm.com" <julien.grall@arm.com>,
Volodymyr Babchuk <Volodymyr_Babchuk@epam.com>
Subject: Re: [Xen-devel] [PATCH v5 2/7] xen/arm: make process_memory_node a device_tree_node_func
Date: Thu, 15 Aug 2019 11:20:27 +0000 [thread overview]
Message-ID: <875zmyhdzi.fsf@epam.com> (raw)
In-Reply-To: <alpine.DEB.2.21.1908141528250.8737@sstabellini-ThinkPad-T480s>
Hi Stefano,
Stefano Stabellini writes:
> On Tue, 13 Aug 2019, Volodymyr Babchuk wrote:
>> > @@ -162,6 +156,10 @@ static void __init process_memory_node(const void *fdt, int node,
>> > bootinfo.mem.bank[bootinfo.mem.nr_banks].size = size;
>> > bootinfo.mem.nr_banks++;
>> > }
>> > +
>> > + if ( bootinfo.mem.nr_banks == NR_MEM_BANKS )
>> > + return -ENOSPC;
>> Are you sure that this logic is correct?
>>
>> For example, if NR_MEM_BANKS is 1, and we have exactly one memory node
>> in device tree, this function will fail. But it should not. I think you
>> want this condition: bootinfo.mem.nr_banks > NR_MEM_BANKS
>
> You are right, if NR_MEM_BANKS is 1 and we have 1 memory node in device
> tree the code would return an error while actually it is normal.
>
> I think the right check would be:
>
> if ( i < banks && bootinfo.mem.nr_banks == NR_MEM_BANKS )
> return -ENOSPC;
Actually, this does not cover all corner cases. Here is the resulting
code:
150 for ( i = 0; i < banks && bootinfo.mem.nr_banks < NR_MEM_BANKS; i++ )
151 {
152 device_tree_get_reg(&cell, address_cells, size_cells, &start, &size);
153 if ( !size )
154 continue;
155 bootinfo.mem.bank[bootinfo.mem.nr_banks].start = start;
156 bootinfo.mem.bank[bootinfo.mem.nr_banks].size = size;
157 bootinfo.mem.nr_banks++;
158 }
159
160 if ( i < banks && bootinfo.mem.nr_banks == NR_MEM_BANKS )
161 return -ENOSPC;
Lines 153-154 cause the issue.
Imagine that NR_MEM_BANKS = 1 and we have two memory nodes in device
tree with. Nodes have sizes 0 and 1024. Your code will work as
intended. At the end of loop we will have banks = 2, i = 2 and
bootinfo.mem.nr_banks = 1.
But if we switch order of memory nodes, so first one will be with size
1024 and second one with size 0, your code will return -ENOSPC, because
we'll have banks = 2, i = 1, bootinfo.mem.nr_banks = 1.
I think, right solution will be to scan all nodes to count nodes
with size > 0. And then - either return an error or do second loop to
fill bootinfo.mem.bank[].
>
> (That's because it is impossible to get to nr_banks > NR_MEM_BANKS.)
Yes, this is my mistake.
--
Volodymyr Babchuk at EPAM
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next prev parent reply other threads:[~2019-08-15 11:21 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-12 22:28 [Xen-devel] [PATCH v5 0/7] reserved-memory in dom0 Stefano Stabellini
2019-08-12 22:28 ` [Xen-devel] [PATCH v5 1/7] xen/arm: pass node to device_tree_for_each_node Stefano Stabellini
2019-08-13 13:45 ` Volodymyr Babchuk
2019-08-14 22:12 ` Stefano Stabellini
2019-08-13 17:25 ` Julien Grall
2019-08-14 22:11 ` Stefano Stabellini
2019-08-12 22:28 ` [Xen-devel] [PATCH v5 2/7] xen/arm: make process_memory_node a device_tree_node_func Stefano Stabellini
2019-08-13 14:14 ` Volodymyr Babchuk
2019-08-14 22:35 ` Stefano Stabellini
2019-08-15 9:12 ` Julien Grall
2019-08-15 11:20 ` Volodymyr Babchuk [this message]
2019-08-15 11:24 ` Julien Grall
2019-08-15 11:29 ` Julien Grall
2019-08-15 12:14 ` Volodymyr Babchuk
2019-08-15 12:33 ` Julien Grall
2019-08-15 13:51 ` Volodymyr Babchuk
2019-08-15 14:15 ` Julien Grall
2019-08-13 17:37 ` Julien Grall
2019-08-14 22:54 ` Stefano Stabellini
2019-08-12 22:28 ` [Xen-devel] [PATCH v5 3/7] xen/arm: keep track of reserved-memory regions Stefano Stabellini
2019-08-13 14:23 ` Volodymyr Babchuk
2019-08-13 14:46 ` Julien Grall
2019-08-13 15:14 ` Volodymyr Babchuk
2019-08-13 15:15 ` Julien Grall
2019-08-13 15:39 ` Volodymyr Babchuk
2019-08-14 12:48 ` Julien Grall
2019-08-12 22:28 ` [Xen-devel] [PATCH v5 4/7] xen/arm: early_print_info print reserved_mem Stefano Stabellini
2019-08-13 14:28 ` Volodymyr Babchuk
2019-08-13 14:47 ` Julien Grall
2019-08-14 22:21 ` Stefano Stabellini
2019-08-14 12:52 ` Julien Grall
2019-08-12 22:28 ` [Xen-devel] [PATCH v5 5/7] xen/arm: handle reserved-memory in consider_modules and dt_unreserved_regions Stefano Stabellini
2019-08-12 22:28 ` [Xen-devel] [PATCH v5 6/7] xen/arm: don't iomem_permit_access for reserved-memory regions Stefano Stabellini
2019-08-13 14:34 ` Volodymyr Babchuk
2019-08-13 14:55 ` Julien Grall
2019-08-14 22:40 ` Stefano Stabellini
2019-08-15 9:15 ` Julien Grall
2019-08-12 22:28 ` [Xen-devel] [PATCH v5 7/7] xen/arm: add reserved-memory regions to the dom0 memory node Stefano Stabellini
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