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 18:44:44 +0200 [thread overview]
Message-ID: <558446FC.6080301@redhat.com> (raw)
In-Reply-To: <20150619183226-mutt-send-email-mst@redhat.com>
On 19/06/2015 18:33, Michael S. Tsirkin wrote:
> On Fri, Jun 19, 2015 at 06:26:27PM +0200, Paolo Bonzini wrote:
>>
>>
>> On 19/06/2015 18:20, Michael S. Tsirkin wrote:
>>>> We could, but I/O is just an example. It can be I/O, a network ring,
>>>> whatever. We cannot audit all address_space_map uses.
>>>>
>>>
>>> No need to audit them all: defer device_add using an hva range until
>>> address_space_unmap drops using hvas in range drops reference count to
>>> 0.
>>
>> That could be forever. You certainly don't want to lockup the monitor
>> forever just because a device model isn't too friendly to memory hot-unplug.
>
> We can defer the addition, no need to lockup the monitor.
Patches are welcome.
>> That's why you need to audit them (also, it's perfectly in the device
>> model's right to use address_space_unmap this way: it's the guest that's
>> buggy and leaves a dangling reference to a region before unplugging it).
>
> Then maybe it's not too bad that the guest will crash because the memory
> was unmapped.
That's a matter of taste. I strongly prefer using 12K extra memory per
VCPU to a guest crash.
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 18:44:44 +0200 [thread overview]
Message-ID: <558446FC.6080301@redhat.com> (raw)
In-Reply-To: <20150619183226-mutt-send-email-mst@redhat.com>
On 19/06/2015 18:33, Michael S. Tsirkin wrote:
> On Fri, Jun 19, 2015 at 06:26:27PM +0200, Paolo Bonzini wrote:
>>
>>
>> On 19/06/2015 18:20, Michael S. Tsirkin wrote:
>>>> We could, but I/O is just an example. It can be I/O, a network ring,
>>>> whatever. We cannot audit all address_space_map uses.
>>>>
>>>
>>> No need to audit them all: defer device_add using an hva range until
>>> address_space_unmap drops using hvas in range drops reference count to
>>> 0.
>>
>> That could be forever. You certainly don't want to lockup the monitor
>> forever just because a device model isn't too friendly to memory hot-unplug.
>
> We can defer the addition, no need to lockup the monitor.
Patches are welcome.
>> That's why you need to audit them (also, it's perfectly in the device
>> model's right to use address_space_unmap this way: it's the guest that's
>> buggy and leaves a dangling reference to a region before unplugging it).
>
> Then maybe it's not too bad that the guest will crash because the memory
> was unmapped.
That's a matter of taste. I strongly prefer using 12K extra memory per
VCPU to a guest crash.
Paolo
--
To unsubscribe from this list: send the line "unsubscribe kvm" in
next prev parent reply other threads:[~2015-06-19 16:44 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 [this message]
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
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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