stable.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Paolo Abeni <pabeni@redhat.com>
To: "Michael Kelley (LINUX)" <mikelley@microsoft.com>,
	Jakub Kicinski <kuba@kernel.org>
Cc: KY Srinivasan <kys@microsoft.com>,
	Haiyang Zhang <haiyangz@microsoft.com>,
	"wei.liu@kernel.org" <wei.liu@kernel.org>,
	Dexuan Cui <decui@microsoft.com>,
	"davem@davemloft.net" <davem@davemloft.net>,
	"edumazet@google.com" <edumazet@google.com>,
	"netdev@vger.kernel.org" <netdev@vger.kernel.org>,
	"linux-hyperv@vger.kernel.org" <linux-hyperv@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"stable@vger.kernel.org" <stable@vger.kernel.org>
Subject: Re: [PATCH net 1/1] hv_netvsc: Fix missed pagebuf entries in netvsc_dma_map/unmap()
Date: Thu, 02 Feb 2023 09:30:45 +0100	[thread overview]
Message-ID: <8a4d08f94d3e6fe8b6da68440eaa89a088ad84f9.camel@redhat.com> (raw)
In-Reply-To: <BYAPR21MB1688B7F47F9ADF2E40E9DEE4D7D69@BYAPR21MB1688.namprd21.prod.outlook.com>

On Thu, 2023-02-02 at 05:20 +0000, Michael Kelley (LINUX) wrote:
> From: Jakub Kicinski <kuba@kernel.org> Sent: Wednesday, February 1, 2023 9:01 PM
> > 
> > On Mon, 30 Jan 2023 19:33:06 -0800 Michael Kelley wrote:
> > > @@ -990,9 +987,7 @@ static int netvsc_dma_map(struct hv_device *hv_dev,
> > >  			  struct hv_netvsc_packet *packet,
> > >  			  struct hv_page_buffer *pb)
> > >  {
> > > -	u32 page_count =  packet->cp_partial ?
> > > -		packet->page_buf_cnt - packet->rmsg_pgcnt :
> > > -		packet->page_buf_cnt;
> > > +	u32 page_count = packet->page_buf_cnt;
> > >  	dma_addr_t dma;
> > >  	int i;
> > 
> > Suspiciously, the caller still does:
> > 
> >                 if (packet->cp_partial)
> >                         pb += packet->rmsg_pgcnt;
> > 
> >                 ret = netvsc_dma_map(ndev_ctx->device_ctx, packet, pb);
> > 
> > Shouldn't that if () pb +=... also go away?
> 
> No -- it's correct.
> 
> In netvsc_send(), cp_partial is tested and packet->page_buf_cnt is
> adjusted.  But the pointer into the pagebuf array is not adjusted in
> netvsc_send().  Instead it is adjusted here in netvsc_send_pkt(), which
> brings it back in sync with packet->page_buf_cnt.

Ok

> I don't know if there's a good reason for the adjustment being split
> across two different functions.  It doesn't seem like the most
> straightforward approach.  From a quick glance at the code it looks
> like this adjustment to 'pb' could move to netvsc_send() to be
> together with the adjustment to packet->page_buf_cnt,  but maybe
> there's a reason for the split that I'm not familiar with.
> 
> Haiyang -- any insight?

While at that, please also have a look at the following allocation in
netvsc_dma_map():

	packet->dma_range = kcalloc(page_count,
                                    sizeof(*packet->dma_range),
                                    GFP_KERNEL);

which looks wrong - netvsc_dma_map() should be in atomic context.

Anyway it's a topic unrelated from this patch. I just stumbled upon it
while reviewing.

Cheers,

Paolo


  reply	other threads:[~2023-02-02  8:31 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-01-31  3:33 [PATCH net 1/1] hv_netvsc: Fix missed pagebuf entries in netvsc_dma_map/unmap() Michael Kelley
2023-01-31 17:01 ` Haiyang Zhang
2023-02-02  5:01 ` Jakub Kicinski
2023-02-02  5:20   ` Michael Kelley (LINUX)
2023-02-02  8:30     ` Paolo Abeni [this message]
2023-02-02 19:24       ` Michael Kelley (LINUX)
2023-02-02  8:40 ` patchwork-bot+netdevbpf

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=8a4d08f94d3e6fe8b6da68440eaa89a088ad84f9.camel@redhat.com \
    --to=pabeni@redhat.com \
    --cc=davem@davemloft.net \
    --cc=decui@microsoft.com \
    --cc=edumazet@google.com \
    --cc=haiyangz@microsoft.com \
    --cc=kuba@kernel.org \
    --cc=kys@microsoft.com \
    --cc=linux-hyperv@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=mikelley@microsoft.com \
    --cc=netdev@vger.kernel.org \
    --cc=stable@vger.kernel.org \
    --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).