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Re: [Qemu-devel] [RFC/PATCH] migration: SMRAM dirty bitmap not fetched f


From: Herongguang (Stephen)
Subject: Re: [Qemu-devel] [RFC/PATCH] migration: SMRAM dirty bitmap not fetched from kvm-kmod and not send to destination
Date: Fri, 23 Sep 2016 17:14:32 +0800
User-agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:38.0) Gecko/20100101 Thunderbird/38.5.1



On 2016/9/23 16:59, Paolo Bonzini wrote:


On 23/09/2016 10:51, Herongguang (Stephen) wrote:


On 2016/9/23 15:17, Paolo Bonzini wrote:


On 22/09/2016 15:16, Herongguang (Stephen) wrote:
I have some concern:
1. For example, vhost does not know about as_id, I wonder if guests in
SMM can operate disk or ether card, as in
that case vhost would not logging dirty pages correctly, without knowing
as_id.

In the end memory is logged by ram_addr_t, not by address space.  So if
vhost_sync_dirty_bitmap is called on the right region everything works.

Guests in SMM can operate on storage devices, but storage devices cannot
write to 0xA0000-0xBFFFF so that's safe.
You are right, as vhost does not have a smram address space listener. So
is this a qemu's flaw that virtual devices can not write to SMRAM?

No, it's how it works in real hardware.  However, it is a (minor) bug
that vhost doesn't have the equivalent of kvm_set_phys_mem's call to
kvm_physical_sync_dirty_bitmap.

Fine, your patch is simpler than I thought and functions right.

Great!

Reviewed-by: He Rongguang <address@hidden>

Also Tested-by?
Yes, I will test this patch in these days.


Thanks,

Paolo

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