From: Paolo Bonzini <pbonzini@redhat.com>
To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Igor Mammedov <imammedo@redhat.com>,
linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
andrey@xdel.ru
Subject: Re: [PATCH 3/5] vhost: support upto 509 memory regions
Date: Fri, 19 Jun 2015 18:50:39 +0200 [thread overview]
Message-ID: <5584485F.8050903@redhat.com> (raw)
In-Reply-To: <20150619184220-mutt-send-email-mst@redhat.com>
On 19/06/2015 18:45, Michael S. Tsirkin wrote:
> > user guest QEMU
> > ----------------------------------------------------------------------------------------
> > start I/O
> > '---------------> address_space_map
> > device_del
> > '-------------------> receives SCI
> > executes _EJ0
> > '---------------> memory_region_del_subregion
> > object_unparent
> > device_add
> > '-----------------------------------------> device_set_realized
> > hotplug_handler_plug
> > pc_machine_device_plug_cb
> > pc_dimm_plug
> > memory_region_add_subregion
> >
> > I/O finishes
> > address_space_unmap
> >
>
> OK so what's the problem with checking for this condition,
> after address_space_unmap detects that ref count is 0
> and before calling mmap(MAP_NORESERVE)?
Should be okay. However, someone still needs to figure out the part
where device_add is delayed until the address_space_unmap. Otherwise,
the device_add's mmap() overlays the older one and the delayed
mmap(MAP_NORESERVE) overlays the device_add's mmap().
It seems like a colossal waste of time to perfect a little-used path
that no doubt will have bugs in it, some of which could perhaps have
security consequences.
Also, QEMU is not the only vhost client, so we're just scratching the
surface here.
Paolo
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WARNING: multiple messages have this Message-ID (diff)
From: Paolo Bonzini <pbonzini@redhat.com>
To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Igor Mammedov <imammedo@redhat.com>,
linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
andrey@xdel.ru
Subject: Re: [PATCH 3/5] vhost: support upto 509 memory regions
Date: Fri, 19 Jun 2015 18:50:39 +0200 [thread overview]
Message-ID: <5584485F.8050903@redhat.com> (raw)
In-Reply-To: <20150619184220-mutt-send-email-mst@redhat.com>
On 19/06/2015 18:45, Michael S. Tsirkin wrote:
> > user guest QEMU
> > ----------------------------------------------------------------------------------------
> > start I/O
> > '---------------> address_space_map
> > device_del
> > '-------------------> receives SCI
> > executes _EJ0
> > '---------------> memory_region_del_subregion
> > object_unparent
> > device_add
> > '-----------------------------------------> device_set_realized
> > hotplug_handler_plug
> > pc_machine_device_plug_cb
> > pc_dimm_plug
> > memory_region_add_subregion
> >
> > I/O finishes
> > address_space_unmap
> >
>
> OK so what's the problem with checking for this condition,
> after address_space_unmap detects that ref count is 0
> and before calling mmap(MAP_NORESERVE)?
Should be okay. However, someone still needs to figure out the part
where device_add is delayed until the address_space_unmap. Otherwise,
the device_add's mmap() overlays the older one and the delayed
mmap(MAP_NORESERVE) overlays the device_add's mmap().
It seems like a colossal waste of time to perfect a little-used path
that no doubt will have bugs in it, some of which could perhaps have
security consequences.
Also, QEMU is not the only vhost client, so we're just scratching the
surface here.
Paolo
next prev parent reply other threads:[~2015-06-19 16:50 UTC|newest]
Thread overview: 80+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-06-16 16:33 [PATCH 0/5] vhost: support upto 509 memory regions Igor Mammedov
2015-06-16 16:33 ` [PATCH 1/5] vhost: use binary search instead of linear in find_region() Igor Mammedov
2015-06-16 21:07 ` Michael S. Tsirkin
2015-06-16 21:13 ` Igor Mammedov
2015-06-16 16:33 ` [PATCH 2/5] vhost: extend memory regions allocation to vmalloc Igor Mammedov
2015-06-16 16:33 ` [PATCH 3/5] vhost: support upto 509 memory regions Igor Mammedov
2015-06-16 21:14 ` Michael S. Tsirkin
2015-06-16 22:00 ` Igor Mammedov
2015-06-17 6:34 ` Michael S. Tsirkin
2015-06-17 7:28 ` Igor Mammedov
2015-06-17 7:39 ` Michael S. Tsirkin
2015-06-17 8:54 ` Igor Mammedov
2015-06-17 10:11 ` Michael S. Tsirkin
2015-06-17 10:37 ` Igor Mammedov
2015-06-17 10:46 ` Michael S. Tsirkin
2015-06-17 11:48 ` Igor Mammedov
2015-06-17 11:51 ` Michael S. Tsirkin
2015-06-17 12:23 ` Igor Mammedov
2015-06-17 13:13 ` Michael S. Tsirkin
2015-06-17 13:20 ` Paolo Bonzini
2015-06-17 14:32 ` Michael S. Tsirkin
2015-06-17 15:12 ` Igor Mammedov
2015-06-17 15:38 ` Michael S. Tsirkin
2015-06-17 16:09 ` Igor Mammedov
2015-06-17 16:30 ` Michael S. Tsirkin
2015-06-17 16:31 ` Paolo Bonzini
2015-06-17 16:34 ` Michael S. Tsirkin
2015-06-17 16:38 ` Paolo Bonzini
2015-06-17 16:41 ` Michael S. Tsirkin
2015-06-17 16:47 ` Paolo Bonzini
2015-06-17 17:32 ` Igor Mammedov
2015-06-17 19:11 ` Michael S. Tsirkin
2015-06-17 17:30 ` Igor Mammedov
2015-06-18 9:12 ` Igor Mammedov
2015-06-18 9:50 ` Michael S. Tsirkin
2015-06-18 10:03 ` Paolo Bonzini
2015-06-18 11:39 ` Igor Mammedov
2015-06-18 11:41 ` Michael S. Tsirkin
2015-06-18 11:50 ` Paolo Bonzini
2015-06-18 13:19 ` Michael S. Tsirkin
2015-06-18 13:46 ` Paolo Bonzini
2015-06-18 14:47 ` Michael S. Tsirkin
2015-06-18 15:54 ` Igor Mammedov
2015-06-18 16:02 ` Paolo Bonzini
2015-06-19 7:56 ` Michael S. Tsirkin
2015-06-19 7:57 ` Paolo Bonzini
2015-06-19 8:05 ` Michael S. Tsirkin
2015-06-19 8:52 ` Paolo Bonzini
2015-06-19 10:14 ` Michael S. Tsirkin
2015-06-19 10:44 ` Paolo Bonzini
2015-06-19 13:34 ` Michael S. Tsirkin
2015-06-19 13:34 ` Michael S. Tsirkin
2015-06-19 15:19 ` Paolo Bonzini
2015-06-19 15:19 ` Paolo Bonzini
2015-06-19 16:20 ` Michael S. Tsirkin
2015-06-19 16:20 ` Michael S. Tsirkin
2015-06-19 16:26 ` Paolo Bonzini
2015-06-19 16:26 ` Paolo Bonzini
2015-06-19 16:33 ` Michael S. Tsirkin
2015-06-19 16:33 ` Michael S. Tsirkin
2015-06-19 16:44 ` Paolo Bonzini
2015-06-19 16:44 ` Paolo Bonzini
2015-06-22 7:10 ` Igor Mammedov
2015-06-22 7:10 ` Igor Mammedov
2015-06-22 9:45 ` Paolo Bonzini
2015-06-22 9:45 ` Paolo Bonzini
2015-06-19 16:45 ` Michael S. Tsirkin
2015-06-19 16:45 ` Michael S. Tsirkin
2015-06-19 16:50 ` Paolo Bonzini [this message]
2015-06-19 16:50 ` Paolo Bonzini
2015-06-18 12:02 ` Igor Mammedov
2015-06-17 8:53 ` Paolo Bonzini
2015-06-16 16:33 ` [PATCH 4/5] vhost: add per VQ memory region caching Igor Mammedov
2015-06-16 16:33 ` [PATCH 5/5] vhost: translate_desc: optimization for desc.len < region size Igor Mammedov
2015-06-16 21:11 ` Michael S. Tsirkin
2015-06-16 21:16 ` [PATCH 0/5] vhost: support upto 509 memory regions Michael S. Tsirkin
2015-06-16 22:19 ` Igor Mammedov
2015-06-17 6:31 ` Michael S. Tsirkin
2015-06-17 7:33 ` Igor Mammedov
2015-06-17 7:40 ` Michael S. Tsirkin
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