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Date: Tue, 14 Oct 2014 07:10:22 +0200
From: Paolo Bonzini <pbonzini@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH] hw/arm/virt: Replace
	memory_region_init_ram with memory_region_allocate_system_memory
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To: Peter Maydell <peter.maydell@linaro.org>, zhuyijun <zhuyijun@huawei.com>
Cc: hangaohuai@huawei.com, QEMU Developers <qemu-devel@nongnu.org>, peter.huangpeng@huawei.com

Il 14/10/2014 06:54, Peter Maydell ha scritto:
> Why is this patch only changing this board? What's special
> about virt that means we don't want to also make this
> change for the other ARM boards? What about all the other
> boards for the other architectures?

-mem-path is not too useful without KVM (TCG is too slow to
notice the difference.  PPC and S390 have already been fixed.

For other boards, I have patches but I had no time to submit
them until now.

> The commit message for 0b183fc871 suggests we decided to
> just break -mem-path for all those boards, which seems an
> odd thing to do... Paolo?

The plan _was_ in fact to fix it up. :(

> Incidentally I can't see anything that guards against
> calling memory_region_allocate_system_memory() twice,
> so I think you would end up with two blocks of RAM
> both backed by the same file then. Or have I misread
> the code?

That would be a bug in the board, it is caught here:

        if (memory_region_is_mapped(seg)) {
            char *path = object_get_canonical_path_component(OBJECT(backend));
            error_report("memory backend %s is used multiple times. Each "
                         "-numa option must use a different memdev value.",
                         path);
            exit(1);
        }

The error message gives the common user error rather than
the less common developer error, but still you catch it.

Paolo