Re: [Qemu-devel] [RFC PATCH v1 0/4] Handle memory hotplug errors from guest OS.

[tangchen]

Forgot to mention, this patch-set is based on the following patch-set:

[RESEND PATCH v3 0/8] QEmu memory hot unplug support.
https://www.mail-archive.com/address@hidden/msg253018.html

Thanks.

On 08/27/2014 04:09 PM, Tang Chen wrote:
> When doing memory hotplug, QEmu is not aware of guest OS error when hotplugging
> memory devices. Even if guest OS failed to hot-add memory, the pc-dimm
> device will be added to QEmu. Even if guest OS failed to hot-remove memory,
> QEmu will remove the pc-dimm device.
>
> An example is: for a Linux guest, the Linux kernel limited that the size of
> hot-added memory should be mutiple of memory section (128MB by default).
> If we add 130MB memory, the Linux kernel won't add it. We are not able
> to handle the size check in QEmu commmand line because different OS may
> have different limits.
>
> And also, QEmu outputs nothing but guest OS failed to hot-add memory will
> confuse users. We should at least report an error.
>
> So, we should report the error to users, and cancel the memory hotplug
> progress in QEmu.
>
> QEmu thread sends a SCI to guest OS and return immediately. The vcpu thread
> will emulate ACPI hardware operations. So this patch-set introduces a wait
> condition variable to synchronize these two threads.
>
> Tang Chen (4):
>    Use macro to define ACPI notification event.
>    Add event handling for memory device insertion.
>    Introduce wait condition to catch guest OS memory hotplug error.
>    Handle memory hotplug error from guest OS in QEmu.
>
>   hw/acpi/memory_hotplug.c | 146 +++++++++++++++++++++++++++++++++++++++++++++--
>   include/hw/acpi/acpi.h   |  15 ++++-
>   2 files changed, 153 insertions(+), 8 deletions(-)