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Date: Thu, 21 Nov 2013 13:48:56 +0800
From: Li Guang <lig.fnst@cn.fujitsu.com>
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Subject: Re: [Qemu-devel] [PATCH 21/27] pc: add memory hotplug 440fx machine
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To: Igor Mammedov <imammedo@redhat.com>
Cc: peter.maydell@linaro.org, aliguori@amazon.com, stefanb@linux.vnet.ibm.com, armbru@redhat.com, mst@redhat.com, mjt@tls.msk.ru, qemu-devel@nongnu.org, mdroth@linux.vnet.ibm.com, vasilis.liaskovitis@profitbricks.com, quintela@redhat.com, kraxel@redhat.com, stefanha@redhat.com, hutao@cn.fujitsu.com, pbonzini@redhat.com, marcel.a@redhat.com, lcapitulino@redhat.com, chegu_vinod@hp.com, afaerber@suse.de

Hi, Igor

Igor Mammedov wrote:
> Add DimmBus for memory hotplug below 4Gb or above 4Gb depending
> on initial memory size and hotplug memory size.
>    
...
> +static
> +void pc_hotplug_memory_init_impl(Object *owner,
> +                                 MemoryRegion *system_memory,
> +                                 ram_addr_t low_hotplug_mem_start,
> +                                 ram_addr_t low_hotplug_mem_end,
> +                                 DimmBus *hotplug_mem_bus,
> +                                 ram_addr_t *high_mem_end)
> +{
> +    QemuOpts *opts = qemu_opts_find(qemu_find_opts("memory-opts"), NULL);
> +    ram_addr_t ram_size = qemu_opt_get_size(opts, "mem", 0);
> +    ram_addr_t maxmem = qemu_opt_get_size(opts, "maxmem", 0);
> +    ram_addr_t hotplug_mem_size;
> +
> +    if (maxmem<= ram_size) {
> +        /* Disable ACPI migration code and creation of memory devices in SSDT */
>    

Why not give the memory that not be hot-added a chance to be placed on 
one memory slot?
if all memory can be hot-added and hot-removed, then we can bring in 
more flexibility for
memory hotplug feature.

Thanks!

> +        qemu_opt_set_number(opts, "slots", 0);
> +        return;
> +    }
> +
> +    hotplug_mem_size = maxmem - ram_size;
> +    if (hotplug_mem_size<= (low_hotplug_mem_end - low_hotplug_mem_start)) {
> +        hotplug_mem_bus->base = low_hotplug_mem_start;
> +    } else {
> +        hotplug_mem_bus->base = ROUND_UP(*high_mem_end, 1ULL<<  30);
> +        *high_mem_end = hotplug_mem_bus->base + hotplug_mem_size;
> +    }
> +
>    
...