Linux USB
 help / color / mirror / Atom feed
From: Mathias Nyman <mathias.nyman@linux.intel.com>
To: oushixiong1025@163.com, Mathias Nyman <mathias.nyman@intel.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org,
	Shixiong Ou <oushixiong@kylinos.cn>
Subject: Re: [PATCH] usb: xhci: fix maximum event ring segments calculation
Date: Mon, 31 Aug 2026 12:10:40 +0300	[thread overview]
Message-ID: <a03c0f9d-02da-4dae-a17c-83412f24566d@linux.intel.com> (raw)
In-Reply-To: <20260828105926.930033-1-oushixiong1025@163.com>

Hi

On 8/28/26 13:59, oushixiong1025@163.com wrote:
> From: Shixiong Ou <oushixiong@kylinos.cn>
> 
> Commit 6d45e9556d4a ("usb: xhci: standardize multi bit-field macros")
> converted BIT(HCS_ERST_MAX(hcs_params2)) into
> FIELD_GET(HCS_ERST_MAX, hcs_params2) << 2. The ERST Max field is a
> power-of-two exponent, so the maximum number of segments is 2^n, not
> n * 4.
> 
> With an ERST Max of 0 (as reported by e.g. QEMU xHCI) max_segs becomes
> 0, the event ring is allocated with 0 segments, and the resulting
> zero-sized ERST allocation trips the page allocator:

Thanks for the report and fix.

This issue was reported earlier and is address in:

https://lore.kernel.org/linux-usb/7e6648ad-7459-4248-8c6c-227cfc2586d8@linux.intel.com/

That patch is on its way upstream.

Good to get verification the fix (very similar) solves the issue for you as well.

Thanks
Mathias


      parent reply	other threads:[~2026-08-31  9:10 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-08-28 10:59 [PATCH] usb: xhci: fix maximum event ring segments calculation oushixiong1025
2026-08-30  3:12 ` Pierre-David Belanger
2026-08-31  6:55   ` Thorsten Leemhuis
2026-08-31  9:21     ` Mathias Nyman
2026-08-31 11:28       ` Thorsten Leemhuis
2026-08-31 11:36         ` Thorsten Leemhuis
2026-08-31 14:28           ` Mathias Nyman
2026-09-01  8:16             ` Thorsten Leemhuis
2026-08-31  9:10 ` Mathias Nyman [this message]

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=a03c0f9d-02da-4dae-a17c-83412f24566d@linux.intel.com \
    --to=mathias.nyman@linux.intel.com \
    --cc=gregkh@linuxfoundation.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-usb@vger.kernel.org \
    --cc=mathias.nyman@intel.com \
    --cc=oushixiong1025@163.com \
    --cc=oushixiong@kylinos.cn \
    /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