From: Andrea Parri <parri.andrea@gmail.com>
To: KY Srinivasan <kys@microsoft.com>,
Haiyang Zhang <haiyangz@microsoft.com>,
Stephen Hemminger <sthemmin@microsoft.com>,
Wei Liu <wei.liu@kernel.org>, Dexuan Cui <decui@microsoft.com>,
Michael Kelley <mikelley@microsoft.com>,
Wei Hu <weh@microsoft.com>,
Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>,
Rob Herring <robh@kernel.org>,
Krzysztof Wilczynski <kw@linux.com>,
Bjorn Helgaas <bhelgaas@google.com>
Cc: linux-hyperv@vger.kernel.org, linux-pci@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [RFC PATCH 1/4] Drivers: hv: vmbus: Remove special code for unsolicited messages
Date: Thu, 7 Apr 2022 04:54:25 +0200 [thread overview]
Message-ID: <20220407025425.GA32474@anparri> (raw)
In-Reply-To: <20220328144244.100228-2-parri.andrea@gmail.com>
On Mon, Mar 28, 2022 at 04:42:41PM +0200, Andrea Parri (Microsoft) wrote:
> vmbus_requestor has included code for handling unsolicited messages
> since its introduction with commit e8b7db38449ac ("Drivers: hv: vmbus:
> Add vmbus_requestor data structure for VMBus hardening"); such code was
> motivated by the early use of vmbus_requestor from storvsc. Since
> storvsc moved to a tag-based mechanism to generate/retrieve request IDs
> with commit bf5fd8cae3c8f ("scsi: storvsc: Use blk_mq_unique_tag() to
> generate requestIDs"), the special handling of unsolicited messages in
> vmbus_requestor is not useful and can be removed.
As it turns out, this is not quite right. In particular...
> @@ -1243,11 +1243,7 @@ u64 vmbus_next_request_id(struct vmbus_channel *channel, u64 rqst_addr)
>
> spin_unlock_irqrestore(&rqstor->req_lock, flags);
>
> - /*
> - * Cannot return an ID of 0, which is reserved for an unsolicited
> - * message from Hyper-V.
> - */
> - return current_id + 1;
> + return current_id;
Hyper-V treats requests with ID of 0 as "non-transactional" and it does
not respond to such requests.
> @@ -1268,15 +1264,8 @@ u64 vmbus_request_addr(struct vmbus_channel *channel, u64 trans_id)
> if (!channel->rqstor_size)
> return VMBUS_NO_RQSTOR;
>
> - /* Hyper-V can send an unsolicited message with ID of 0 */
> - if (!trans_id)
> - return trans_id;
This remains problematic: I will elaborate and propose some solution in
the next iteration (to be sent shortly).
Thanks,
Andrea
> -
> spin_lock_irqsave(&rqstor->req_lock, flags);
>
> - /* Data corresponding to trans_id is stored at trans_id - 1 */
> - trans_id--;
> -
> /* Invalid trans_id */
> if (trans_id >= rqstor->size || !test_bit(trans_id, rqstor->req_bitmap)) {
> spin_unlock_irqrestore(&rqstor->req_lock, flags);
next prev parent reply other threads:[~2022-04-07 2:54 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-03-28 14:42 [RFC PATCH 0/4] PCI: hv: Miscellaneous changes Andrea Parri (Microsoft)
2022-03-28 14:42 ` [RFC PATCH 1/4] Drivers: hv: vmbus: Remove special code for unsolicited messages Andrea Parri (Microsoft)
2022-03-31 18:00 ` Michael Kelley (LINUX)
2022-04-07 2:54 ` Andrea Parri [this message]
2022-03-28 14:42 ` [RFC PATCH 2/4] PCI: hv: Use vmbus_requestor to generate transaction IDs for VMbus hardening Andrea Parri (Microsoft)
2022-03-31 18:12 ` Michael Kelley (LINUX)
2022-04-01 16:00 ` Andrea Parri
2022-03-28 14:42 ` [RFC PATCH 3/4] Drivers: hv: vmbus: Introduce vmbus_sendpacket_getid() Andrea Parri (Microsoft)
2022-03-31 19:47 ` Michael Kelley (LINUX)
2022-04-01 16:09 ` Andrea Parri
2022-03-28 14:42 ` [RFC PATCH 4/4] PCI: hv: Fix synchronization between channel callback and hv_compose_msi_msg() Andrea Parri (Microsoft)
2022-03-31 20:04 ` Michael Kelley (LINUX)
2022-04-01 16:30 ` Andrea Parri
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