From: Sunil Muthuswamy <sunilmut@microsoft.com>
To: Tianyu Lan <ltykernel@gmail.com>, Christoph Hellwig <hch@infradead.org>
Cc: KY Srinivasan <kys@microsoft.com>,
Haiyang Zhang <haiyangz@microsoft.com>,
Stephen Hemminger <sthemmin@microsoft.com>,
"wei.liu@kernel.org" <wei.liu@kernel.org>,
"jejb@linux.ibm.com" <jejb@linux.ibm.com>,
"martin.petersen@oracle.com" <martin.petersen@oracle.com>,
Tianyu Lan <Tianyu.Lan@microsoft.com>,
"linux-hyperv@vger.kernel.org" <linux-hyperv@vger.kernel.org>,
"linux-scsi@vger.kernel.org" <linux-scsi@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
vkuznets <vkuznets@redhat.com>,
"thomas.lendacky@amd.com" <thomas.lendacky@amd.com>,
"brijesh.singh@amd.com" <brijesh.singh@amd.com>
Subject: RE: [EXTERNAL] Re: [RFC PATCH 12/12] HV/Storvsc: Add bounce buffer support for Storvsc
Date: Mon, 1 Mar 2021 19:45:36 +0000 [thread overview]
Message-ID: <SN4PR2101MB088022E836AEC0838266A8C6C09A9@SN4PR2101MB0880.namprd21.prod.outlook.com> (raw)
In-Reply-To: <9a5d3809-f1e1-0f4a-8249-9ce1c6df6453@gmail.com>
> Hi Christoph:
> Thanks a lot for your review. There are some reasons.
> 1) Vmbus drivers don't use DMA API now.
What is blocking us from making the Hyper-V drivers use the DMA API's? They
will be a null-op generally, when there is no bounce buffer support needed.
> 2) Hyper-V Vmbus channel ring buffer already play bounce buffer
> role for most vmbus drivers. Just two kinds of packets from
> netvsc/storvsc are uncovered.
How does this make a difference here?
> 3) In AMD SEV-SNP based Hyper-V guest, the access physical address
> of shared memory should be bounce buffer memory physical address plus
> with a shared memory boundary(e.g, 48bit) reported Hyper-V CPUID. It's
> called virtual top of memory(vTom) in AMD spec and works as a watermark.
> So it needs to ioremap/memremap the associated physical address above
> the share memory boundary before accessing them. swiotlb_bounce() uses
> low end physical address to access bounce buffer and this doesn't work
> in this senario. If something wrong, please help me correct me.
>
There are alternative implementations of swiotlb on top of the core swiotlb
API's. One option is to have Hyper-V specific swiotlb wrapper DMA API's with
the custom logic above.
> Thanks.
>
>
> On 3/1/2021 2:54 PM, Christoph Hellwig wrote:
> > This should be handled by the DMA mapping layer, just like for native
> > SEV support.
I agree with Christoph's comment that in principle, this should be handled using
the DMA API's
next prev parent reply other threads:[~2021-03-02 4:43 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-28 15:03 [RFC PATCH 00/12] x86/Hyper-V: Add Hyper-V Isolation VM support Tianyu Lan
2021-02-28 15:03 ` [RFC PATCH 1/12] x86/Hyper-V: Add visibility parameter for vmbus_establish_gpadl() Tianyu Lan
2021-03-03 16:27 ` Vitaly Kuznetsov
2021-03-05 6:06 ` Tianyu Lan
2021-02-28 15:03 ` [RFC PATCH 2/12] x86/Hyper-V: Add new hvcall guest address host visibility support Tianyu Lan
2021-03-03 16:58 ` Vitaly Kuznetsov
2021-03-05 6:23 ` Tianyu Lan
2021-02-28 15:03 ` [RFC PATCH 3/12] x86/HV: Initialize GHCB page and shared memory boundary Tianyu Lan
2021-03-03 17:05 ` Vitaly Kuznetsov
2021-02-28 15:03 ` [RFC PATCH 4/12] HV: Add Write/Read MSR registers via ghcb Tianyu Lan
2021-03-03 17:16 ` Vitaly Kuznetsov
2021-03-05 6:37 ` Tianyu Lan
2021-02-28 15:03 ` [RFC PATCH 5/12] HV: Add ghcb hvcall support for SNP VM Tianyu Lan
2021-03-03 17:21 ` Vitaly Kuznetsov
2021-03-05 15:21 ` Tianyu Lan
2021-02-28 15:03 ` [RFC PATCH 6/12] HV/Vmbus: Add SNP support for VMbus channel initiate message Tianyu Lan
2021-02-28 15:03 ` [RFC PATCH 7/12] hv/vmbus: Initialize VMbus ring buffer for Isolation VM Tianyu Lan
2021-02-28 15:03 ` [RFC PATCH 8/12] x86/Hyper-V: Initialize bounce buffer page cache and list Tianyu Lan
2021-02-28 15:03 ` [RFC PATCH 9/12] x86/Hyper-V: Add new parameter for vmbus_sendpacket_pagebuffer()/mpb_desc() Tianyu Lan
2021-02-28 15:03 ` [RFC PATCH 10/12] HV: Add bounce buffer support for Isolation VM Tianyu Lan
2021-02-28 15:03 ` [RFC PATCH 11/12] HV/Netvsc: Add Isolation VM support for netvsc driver Tianyu Lan
2021-02-28 15:03 ` [RFC PATCH 12/12] HV/Storvsc: Add bounce buffer support for Storvsc Tianyu Lan
2021-03-01 6:54 ` Christoph Hellwig
2021-03-01 13:43 ` Tianyu Lan
2021-03-01 19:45 ` Sunil Muthuswamy [this message]
2021-03-02 16:03 ` [EXTERNAL] " Tianyu Lan
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=SN4PR2101MB088022E836AEC0838266A8C6C09A9@SN4PR2101MB0880.namprd21.prod.outlook.com \
--to=sunilmut@microsoft.com \
--cc=Tianyu.Lan@microsoft.com \
--cc=brijesh.singh@amd.com \
--cc=haiyangz@microsoft.com \
--cc=hch@infradead.org \
--cc=jejb@linux.ibm.com \
--cc=kys@microsoft.com \
--cc=linux-hyperv@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-scsi@vger.kernel.org \
--cc=ltykernel@gmail.com \
--cc=martin.petersen@oracle.com \
--cc=sthemmin@microsoft.com \
--cc=thomas.lendacky@amd.com \
--cc=vkuznets@redhat.com \
--cc=wei.liu@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).