From: Maxime Coquelin <maxime.coquelin@redhat.com>
To: Yuanhan Liu <yliu@fridaylinux.org>
Cc: dev@dpdk.org, jfreiman@redhat.com, tiwei.bie@intel.com,
mst@redhat.com, vkaplans@redhat.com, jasowang@redhat.com
Subject: Re: [dpdk-dev] [PATCH 07/21] vhost: add iotlb helper functions
Date: Fri, 8 Sep 2017 11:28:57 +0200 [thread overview]
Message-ID: <86ce8050-e346-2c4e-5eed-f6134c7c8fc6@redhat.com> (raw)
In-Reply-To: <20170908092121.GH9736@yliu-home>
On 09/08/2017 11:21 AM, Yuanhan Liu wrote:
> On Fri, Sep 08, 2017 at 10:50:49AM +0200, Maxime Coquelin wrote:
>>>>>> +{
>>>>>> + struct vhost_iotlb_entry *node, *temp_node;
>>>>>> +
>>>>>> + rte_rwlock_write_lock(&vq->iotlb_lock);
>>>>>> +
>>>>>> + TAILQ_FOREACH_SAFE(node, &vq->iotlb_list, next, temp_node) {
>>>>>> + TAILQ_REMOVE(&vq->iotlb_list, node, next);
>>>>>> + rte_mempool_put(vq->iotlb_pool, node);
>>>>>> + }
>>>>>> +
>>>>>> + rte_rwlock_write_unlock(&vq->iotlb_lock);
>>>>>> +}
>>>>>> +
>>>>>> +void vhost_user_iotlb_cache_insert(struct vhost_virtqueue *vq, uint64_t iova,
>>>>>> + uint64_t uaddr, uint64_t size, uint8_t perm)
>>>>>> +{
>>>>>> + struct vhost_iotlb_entry *node, *new_node;
>>>>>> + int ret;
>>>>>> +
>>>>>> + ret = rte_mempool_get(vq->iotlb_pool, (void **)&new_node);
>>>>>> + if (ret) {
>>>>>> + RTE_LOG(ERR, VHOST_CONFIG, "IOTLB pool empty, invalidate cache\n");
>>>>>
>>>>> It's a cache, why not considering remove one to get space for new one?
>>>>
>>>> It would mean having to track every lookups not to remove hot entries,
>>>> which would have an impact on performance.
>>>
>>> You were removing all caches, how can we do worse than that? Even a
>>> random evict would be better. Or, more simply, just to remove the
>>> head or the tail?
>>
>> I think removing head or tail could cause deadlocks.
>> For example it needs to translate from 0x0 to 0x2000, with page size
>> being 0x1000.
>>
>> If cache is full, when inserting 0x1000-0x1fff, it will remove
>> 0x0-0xfff, so a miss will be sent for 0x0-0xffff and 0x1000-0x1fff will
>> be remove at insert time, etc...
>
> Okay, that means we can't simply remove the head or tail.
>
>> Note that we really need to size the cache large enough for performance
>> purpose, so having the cache full could be cause by either buggy or
>> malicious guest.
>
> I agree. But for the malicious guest, it could lead to a DDOS attack:
> assume it keeps vhost running out of cache and then vhost keeps printing
> above message.
>
> What I suggested was to evict one (by some polices) to get a space for
> the new one we want to insert. Note that it won't be a performance issue,
> IMO, due to we only do that when we run out of caches, which, according
> to your sayings, should not happen in normal cases.
Ok, so let's randomly remove one entry. What about using something like:
rte_rand() % IOTLB_CACHE_SIZE
>
> --yliu
>
>>>> Moreover, the idea is to have the cache large enough, else you could
>>>> face packet drops due to random cache misses.
>>>>
>>>> We might consider to improve it, but I consider it an optimization that
>>>> could be implemented later if needed.
>>>>
>>>>>> + vhost_user_iotlb_cache_remove_all(vq);
>>>>>> + ret = rte_mempool_get(vq->iotlb_pool, (void **)&new_node);
>>>>>> + if (ret) {
>>>>>> + RTE_LOG(ERR, VHOST_CONFIG, "IOTLB pool still empty, failure\n");
>>>>>> + return;
>>>>>> + }
>>>>>> + }
next prev parent reply other threads:[~2017-09-08 9:29 UTC|newest]
Thread overview: 59+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-08-31 9:50 [dpdk-dev] [PATCH 00/21] Vhost-user: Implement device IOTLB support Maxime Coquelin
2017-08-31 9:50 ` [dpdk-dev] [PATCH 01/21] Revert "vhost: workaround MQ fails to startup" Maxime Coquelin
2017-09-07 11:54 ` Yuanhan Liu
2017-09-07 12:59 ` Maxime Coquelin
2017-09-24 10:41 ` Maxime Coquelin
2017-08-31 9:50 ` [dpdk-dev] [PATCH 02/21] vhost: make error handling consistent in rx path Maxime Coquelin
2017-08-31 9:50 ` [dpdk-dev] [PATCH 03/21] vhost: protect virtio_net device struct Maxime Coquelin
2017-09-05 4:45 ` Tiwei Bie
2017-09-05 9:24 ` Maxime Coquelin
2017-09-05 10:07 ` Tiwei Bie
2017-09-05 11:00 ` Maxime Coquelin
2017-09-06 1:15 ` Tiwei Bie
2017-09-06 2:59 ` Stephen Hemminger
2017-09-06 7:50 ` Maxime Coquelin
2017-09-06 7:15 ` Maxime Coquelin
2017-09-06 7:30 ` Tiwei Bie
2017-09-06 20:02 ` Maxime Coquelin
2017-09-07 5:08 ` Tiwei Bie
2017-09-07 13:44 ` Yuanhan Liu
2017-09-07 14:01 ` Maxime Coquelin
2017-08-31 9:50 ` [dpdk-dev] [PATCH 04/21] vhost: prepare send_vhost_message() to slave requests Maxime Coquelin
2017-08-31 9:50 ` [dpdk-dev] [PATCH 05/21] vhost: add support to slave requests channel Maxime Coquelin
2017-09-05 4:19 ` Tiwei Bie
2017-09-05 8:18 ` Maxime Coquelin
2017-08-31 9:50 ` [dpdk-dev] [PATCH 06/21] vhost: declare missing IOMMU-related definitions for old kernels Maxime Coquelin
2017-08-31 9:50 ` [dpdk-dev] [PATCH 07/21] vhost: add iotlb helper functions Maxime Coquelin
2017-09-05 6:02 ` Tiwei Bie
2017-09-05 15:16 ` Maxime Coquelin
2017-09-08 8:08 ` Yuanhan Liu
2017-09-08 8:24 ` Maxime Coquelin
2017-09-08 8:36 ` Yuanhan Liu
2017-09-08 8:50 ` Maxime Coquelin
2017-09-08 9:21 ` Yuanhan Liu
2017-09-08 9:28 ` Maxime Coquelin [this message]
2017-08-31 9:50 ` [dpdk-dev] [PATCH 08/21] vhost: iotlb: add pending miss request list and helpers Maxime Coquelin
2017-09-05 7:11 ` Tiwei Bie
2017-09-05 15:18 ` Maxime Coquelin
2017-08-31 9:50 ` [dpdk-dev] [PATCH 09/21] vhost-user: add support to IOTLB miss slave requests Maxime Coquelin
2017-08-31 9:50 ` [dpdk-dev] [PATCH 10/21] vhost: initialize vrings IOTLB caches Maxime Coquelin
2017-09-04 13:57 ` Remy Horton
2017-09-04 15:45 ` Maxime Coquelin
2017-08-31 9:50 ` [dpdk-dev] [PATCH 11/21] vhost-user: handle IOTLB update and invalidate requests Maxime Coquelin
2017-08-31 9:50 ` [dpdk-dev] [PATCH 12/21] vhost: introduce guest IOVA to backend VA helper Maxime Coquelin
2017-09-05 4:14 ` Tiwei Bie
2017-09-05 7:05 ` Maxime Coquelin
2017-08-31 9:50 ` [dpdk-dev] [PATCH 13/21] vhost: use the guest IOVA to host " Maxime Coquelin
2017-08-31 9:50 ` [dpdk-dev] [PATCH 14/21] vhost: enable rings at the right time Maxime Coquelin
2017-08-31 9:50 ` [dpdk-dev] [PATCH 15/21] vhost: don't dereference invalid dev pointer after its reallocation Maxime Coquelin
2017-09-04 13:58 ` Remy Horton
2017-08-31 9:50 ` [dpdk-dev] [PATCH 16/21] vhost: postpone rings addresses translation Maxime Coquelin
2017-08-31 9:50 ` [dpdk-dev] [PATCH 17/21] vhost-user: translate ring addresses when IOMMU enabled Maxime Coquelin
2017-08-31 9:50 ` [dpdk-dev] [PATCH 18/21] vhost-user: iommu: postpone device creation until ring are mapped Maxime Coquelin
2017-08-31 9:50 ` [dpdk-dev] [PATCH 19/21] vhost: iommu: Invalidate vring in case of matching IOTLB invalidate Maxime Coquelin
2017-08-31 9:50 ` [dpdk-dev] [PATCH 20/21] vhost: enable IOMMU support Maxime Coquelin
2017-08-31 9:50 ` [dpdk-dev] [PATCH 21/21] vhost: iotlb: reduce iotlb read lock usage Maxime Coquelin
2017-09-11 4:18 ` Yuanhan Liu
2017-09-11 7:34 ` Maxime Coquelin
2017-09-11 9:39 ` Yuanhan Liu
2017-09-04 13:58 ` [dpdk-dev] [PATCH 00/21] Vhost-user: Implement device IOTLB support Remy Horton
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