From: "Michael Kelley (LINUX)" <mikelley@microsoft.com>
To: Yanming Liu <yanminglr@gmail.com>
Cc: Wei Liu <wei.liu@kernel.org>,
Andrea Parri <parri.andrea@gmail.com>,
"linux-hyperv@vger.kernel.org" <linux-hyperv@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"dri-devel@lists.freedesktop.org"
<dri-devel@lists.freedesktop.org>,
"linux-fbdev@vger.kernel.org" <linux-fbdev@vger.kernel.org>,
KY Srinivasan <kys@microsoft.com>,
Haiyang Zhang <haiyangz@microsoft.com>,
Stephen Hemminger <sthemmin@microsoft.com>,
Dexuan Cui <decui@microsoft.com>,
"drawat.floss@gmail.com" <drawat.floss@gmail.com>,
"airlied@linux.ie" <airlied@linux.ie>,
"daniel@ffwll.ch" <daniel@ffwll.ch>,
"lkmlabelt@gmail.com" <lkmlabelt@gmail.com>
Subject: RE: [PATCH v2] hv: account for packet descriptor in maximum packet size
Date: Thu, 27 Jan 2022 21:22:34 +0000 [thread overview]
Message-ID: <MWHPR21MB1593F5A0494D7726E577E03DD7219@MWHPR21MB1593.namprd21.prod.outlook.com> (raw)
In-Reply-To: <CAH+BkoGWu7BgEJo9+c3kAcyEf1qptvmts1DMoW4RoP=3e7eN7Q@mail.gmail.com>
From: Yanming Liu <yanminglr@gmail.com> Sent: Wednesday, January 19, 2022 12:14 PM
>
> On Thu, Jan 20, 2022 at 2:12 AM Michael Kelley (LINUX)
> <mikelley@microsoft.com> wrote:
> >
> > From: Wei Liu <wei.liu@kernel.org> Sent: Friday, January 14, 2022 11:13 AM
> > >
> > > On Mon, Jan 10, 2022 at 01:44:19AM +0100, Andrea Parri wrote:
> > > > (Extending Cc: list,)
> > > >
> > > > On Sun, Jan 09, 2022 at 05:55:16PM +0800, Yanming Liu wrote:
> >
> > The VSS driver in hv_snapshot.c allocates a receive buffer of 8 Kbytes
> > and sets max_pkt_size to 8 Kbytes. But the received messages are
> > all fixed size and small. I don't know why the driver uses an 8 Kbyte
> > receive buffer instead of 4 Kbytes, but the current settings are
> > more than sufficient.
> >
>
> Well, I'm not sure, on August 2021 there was a patch changing
> max_pkt_size to 8 KiB for VSS driver:
> https://lore.kernel.org/linux-hyperv/20210825190217.qh2c6yq5qr3ntum5@liuwe-devbox-debian-v2/T/
>
> The patch mentioned a 6304 bytes VSS message. Which is part of the
> reason I tried to address the more "general" problem of potentially
> mismatching buffer size.
>
This is certainly interesting. The Linux driver is not processing
all those bytes, so I'm not sure what Hyper-V is passing to the
guest. I'll check with the Hyper-V team to be sure.
Michael
WARNING: multiple messages have this Message-ID (diff)
From: "Michael Kelley (LINUX)" <mikelley@microsoft.com>
To: Yanming Liu <yanminglr@gmail.com>
Cc: Andrea Parri <parri.andrea@gmail.com>,
Wei Liu <wei.liu@kernel.org>,
Stephen Hemminger <sthemmin@microsoft.com>,
"lkmlabelt@gmail.com" <lkmlabelt@gmail.com>,
"linux-hyperv@vger.kernel.org" <linux-hyperv@vger.kernel.org>,
"airlied@linux.ie" <airlied@linux.ie>,
Haiyang Zhang <haiyangz@microsoft.com>,
Dexuan Cui <decui@microsoft.com>,
"linux-fbdev@vger.kernel.org" <linux-fbdev@vger.kernel.org>,
"dri-devel@lists.freedesktop.org"
<dri-devel@lists.freedesktop.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"drawat.floss@gmail.com" <drawat.floss@gmail.com>,
KY Srinivasan <kys@microsoft.com>
Subject: RE: [PATCH v2] hv: account for packet descriptor in maximum packet size
Date: Thu, 27 Jan 2022 21:22:34 +0000 [thread overview]
Message-ID: <MWHPR21MB1593F5A0494D7726E577E03DD7219@MWHPR21MB1593.namprd21.prod.outlook.com> (raw)
In-Reply-To: <CAH+BkoGWu7BgEJo9+c3kAcyEf1qptvmts1DMoW4RoP=3e7eN7Q@mail.gmail.com>
From: Yanming Liu <yanminglr@gmail.com> Sent: Wednesday, January 19, 2022 12:14 PM
>
> On Thu, Jan 20, 2022 at 2:12 AM Michael Kelley (LINUX)
> <mikelley@microsoft.com> wrote:
> >
> > From: Wei Liu <wei.liu@kernel.org> Sent: Friday, January 14, 2022 11:13 AM
> > >
> > > On Mon, Jan 10, 2022 at 01:44:19AM +0100, Andrea Parri wrote:
> > > > (Extending Cc: list,)
> > > >
> > > > On Sun, Jan 09, 2022 at 05:55:16PM +0800, Yanming Liu wrote:
> >
> > The VSS driver in hv_snapshot.c allocates a receive buffer of 8 Kbytes
> > and sets max_pkt_size to 8 Kbytes. But the received messages are
> > all fixed size and small. I don't know why the driver uses an 8 Kbyte
> > receive buffer instead of 4 Kbytes, but the current settings are
> > more than sufficient.
> >
>
> Well, I'm not sure, on August 2021 there was a patch changing
> max_pkt_size to 8 KiB for VSS driver:
> https://lore.kernel.org/linux-hyperv/20210825190217.qh2c6yq5qr3ntum5@liuwe-devbox-debian-v2/T/
>
> The patch mentioned a 6304 bytes VSS message. Which is part of the
> reason I tried to address the more "general" problem of potentially
> mismatching buffer size.
>
This is certainly interesting. The Linux driver is not processing
all those bytes, so I'm not sure what Hyper-V is passing to the
guest. I'll check with the Hyper-V team to be sure.
Michael
next prev parent reply other threads:[~2022-01-27 21:22 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-01-09 9:55 [PATCH v2] hv: account for packet descriptor in maximum packet size Yanming Liu
2022-01-10 0:44 ` Andrea Parri
2022-01-10 0:44 ` Andrea Parri
2022-01-14 19:13 ` Wei Liu
2022-01-14 19:13 ` Wei Liu
2022-01-19 18:12 ` Michael Kelley (LINUX)
2022-01-19 18:12 ` Michael Kelley (LINUX)
2022-01-19 20:13 ` Yanming Liu
2022-01-19 20:13 ` Yanming Liu
2022-01-27 21:22 ` Michael Kelley (LINUX) [this message]
2022-01-27 21:22 ` Michael Kelley (LINUX)
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