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From: Tianyu Lan <ltykernel@gmail.com>
To: Christoph Hellwig <hch@lst.de>
Cc: kys@microsoft.com, haiyangz@microsoft.com,
	sthemmin@microsoft.com, wei.liu@kernel.org, decui@microsoft.com,
	catalin.marinas@arm.com, will@kernel.org, tglx@linutronix.de,
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	dave.hansen@linux.intel.com, luto@kernel.org,
	peterz@infradead.org, konrad.wilk@oracle.com,
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	sstabellini@kernel.org, joro@8bytes.org, davem@davemloft.net,
	kuba@kernel.org, jejb@linux.ibm.com, martin.petersen@oracle.com,
	gregkh@linuxfoundation.org, arnd@arndb.de,
	m.szyprowski@samsung.com, robin.murphy@arm.com,
	brijesh.singh@amd.com, thomas.lendacky@amd.com,
	Tianyu.Lan@microsoft.com, pgonda@google.com,
	martin.b.radev@gmail.com, akpm@linux-foundation.org,
	kirill.shutemov@linux.intel.com, rppt@kernel.org,
	hannes@cmpxchg.org, aneesh.kumar@linux.ibm.com,
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	linux-arm-kernel@lists.infradead.org,
	xen-devel@lists.xenproject.org, rientjes@google.com,
	ardb@kernel.org, michael.h.kelley@microsoft.com,
	iommu@lists.linux-foundation.org, linux-arch@vger.kernel.org,
	linux-hyperv@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-scsi@vger.kernel.org, netdev@vger.kernel.org,
	vkuznets@redhat.com, parri.andrea@gmail.com,
	dave.hansen@intel.com
Subject: Re: [PATCH V4 00/13] x86/Hyper-V: Add Hyper-V Isolation VM support
Date: Tue, 31 Aug 2021 23:20:06 +0800	[thread overview]
Message-ID: <91b5e997-8d44-77f0-6519-f574b541ba9f@gmail.com> (raw)
In-Reply-To: <20210830120036.GA22005@lst.de>

Hi Christoph:

On 8/30/2021 8:00 PM, Christoph Hellwig wrote:
> Sorry for the delayed answer, but I look at the vmap_pfn usage in the
> previous version and tried to come up with a better version.  This
> mostly untested branch:
> 
> http://git.infradead.org/users/hch/misc.git/shortlog/refs/heads/hyperv-vmap

No problem. Thank you very much for your suggestion patches and they are 
very helpful.


> 
> get us there for swiotlb and the channel infrastructure  I've started
> looking at the network driver and didn't get anywhere due to other work.
> 
> As far as I can tell the network driver does gigantic multi-megabyte
> vmalloc allocation for the send and receive buffers, which are then
> passed to the hardware, but always copied to/from when interacting
> with the networking stack.  Did I see that right?  Are these big
> buffers actually required unlike the normal buffer management schemes
> in other Linux network drivers?


For send packet, netvsc tries batching packet in send buffer if 
possible. It passes the original skb pages directly to
hypervisor when send buffer is not enough or packet length is larger 
than section size. These packets are sent via 
vmbus_sendpacket_pagebuffer() finally. Please see netvsc_send() for 
detail. The following code is to check whether the packet could be 
copied into send buffer. If not, the packet will be sent with original 
skb pages.

1239        /* batch packets in send buffer if possible */
1240        msdp = &nvchan->msd;
1241        if (msdp->pkt)
1242                msd_len = msdp->pkt->total_data_buflen;
1243
1244        try_batch =  msd_len > 0 && msdp->count < net_device->max_pkt;
1245        if (try_batch && msd_len + pktlen + net_device->pkt_align <
1246            net_device->send_section_size) {
1247                section_index = msdp->pkt->send_buf_index;
1248
1249        } else if (try_batch && msd_len + packet->rmsg_size <
1250                   net_device->send_section_size) {
1251                section_index = msdp->pkt->send_buf_index;
1252                packet->cp_partial = true;
1253
1254        } else if (pktlen + net_device->pkt_align <
1255                   net_device->send_section_size) {
1256                section_index = 
netvsc_get_next_send_section(net_device);
1257                if (unlikely(section_index == NETVSC_INVALID_INDEX)) {
1258                        ++ndev_ctx->eth_stats.tx_send_full;
1259                } else {
1260                        move_pkt_msd(&msd_send, &msd_skb, msdp);
1261                        msd_len = 0;
1262                }
1263        }
1264



For receive packet, the data is always copied from recv buffer.

> 
> If so I suspect the best way to allocate them is by not using vmalloc
> but just discontiguous pages, and then use kmap_local_pfn where the
> PFN includes the share_gpa offset when actually copying from/to the
> skbs.
> 
When netvsc needs to copy packet data to send buffer, it needs to 
caculate position with section_index and send_section_size.
Please seee netvsc_copy_to_send_buf() detail. So the contiguous virtual 
address of send buffer is necessary to copy data and batch packets.

  reply	other threads:[~2021-08-31 15:20 UTC|newest]

Thread overview: 41+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-27 17:20 Tianyu Lan
2021-08-27 17:20 ` [PATCH V4 01/13] x86/hyperv: Initialize GHCB page in Isolation VM Tianyu Lan
2021-09-02  0:15   ` Michael Kelley
2021-08-27 17:21 ` [PATCH V4 02/13] x86/hyperv: Initialize shared memory boundary in the " Tianyu Lan
2021-09-02  0:15   ` Michael Kelley
2021-09-02  6:35     ` Tianyu Lan
2021-08-27 17:21 ` [PATCH V4 03/13] x86/hyperv: Add new hvcall guest address host visibility support Tianyu Lan
2021-09-02  0:16   ` Michael Kelley
2021-08-27 17:21 ` [PATCH V4 04/13] hyperv: Mark vmbus ring buffer visible to host in Isolation VM Tianyu Lan
2021-08-27 17:41   ` Greg KH
2021-08-27 17:44     ` Tianyu Lan
2021-09-02  0:17   ` Michael Kelley
2021-08-27 17:21 ` [PATCH V4 05/13] hyperv: Add Write/Read MSR registers via ghcb page Tianyu Lan
2021-08-27 17:41   ` Greg KH
2021-08-27 17:46     ` Tianyu Lan
2021-09-02  3:32   ` Michael Kelley
2021-08-27 17:21 ` [PATCH V4 06/13] hyperv: Add ghcb hvcall support for SNP VM Tianyu Lan
2021-09-02  0:20   ` Michael Kelley
2021-08-27 17:21 ` [PATCH V4 07/13] hyperv/Vmbus: Add SNP support for VMbus channel initiate message Tianyu Lan
2021-09-02  0:21   ` Michael Kelley
2021-08-27 17:21 ` [PATCH V4 08/13] hyperv/vmbus: Initialize VMbus ring buffer for Isolation VM Tianyu Lan
2021-09-02  0:23   ` Michael Kelley
2021-09-02 13:35     ` Tianyu Lan
2021-09-02 16:14       ` Michael Kelley
2021-08-27 17:21 ` [PATCH V4 09/13] DMA: Add dma_map_decrypted/dma_unmap_encrypted() function Tianyu Lan
2021-08-27 17:21 ` [PATCH V4 10/13] x86/Swiotlb: Add Swiotlb bounce buffer remap function for HV IVM Tianyu Lan
2021-08-27 17:21 ` [PATCH V4 11/13] hyperv/IOMMU: Enable swiotlb bounce buffer for Isolation VM Tianyu Lan
2021-09-02  1:27   ` Michael Kelley
2021-08-27 17:21 ` [PATCH V4 12/13] hv_netvsc: Add Isolation VM support for netvsc driver Tianyu Lan
2021-09-02  2:34   ` Michael Kelley
2021-09-02  4:56     ` Michael Kelley
2021-08-27 17:21 ` [PATCH V4 13/13] hv_storvsc: Add Isolation VM support for storvsc driver Tianyu Lan
2021-09-02  2:08   ` Michael Kelley
2021-08-30 12:00 ` [PATCH V4 00/13] x86/Hyper-V: Add Hyper-V Isolation VM support Christoph Hellwig
2021-08-31 15:20   ` Tianyu Lan [this message]
2021-09-02  7:51     ` Christoph Hellwig
2021-08-31 17:16   ` Michael Kelley
2021-09-02  7:59     ` Christoph Hellwig
2021-09-02 11:21       ` Tianyu Lan
2021-09-02 15:57       ` Michael Kelley
2021-09-14 14:41         ` Tianyu Lan

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