From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id F3023E95A8E for ; Mon, 9 Oct 2023 09:10:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1345639AbjJIJKt (ORCPT ); Mon, 9 Oct 2023 05:10:49 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41642 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234489AbjJIJKr (ORCPT ); Mon, 9 Oct 2023 05:10:47 -0400 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id CCC95A3; Mon, 9 Oct 2023 02:10:45 -0700 (PDT) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 41527C433C7; Mon, 9 Oct 2023 09:10:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1696842645; bh=f5CUYsknjVmhnuTqhXtkJxqt3bb4YSHlTfNzYrnpBuU=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=fz+BE5xuLV3Yh0jSKKwKBi28SNwZP6ko5HrzaOLCMXAY3v0jAslsCOFIJyBQlOWa3 3+peKOxVHoeX+jBrhdicviDhC3uZ9e58+jIh5tCIfOXjup1W5xSe02ogt/NWiBvoB9 tVz/7Vc6CvgLRNXOevRFKX7Tlkqzps/0zBUYC/cpIPJdMHL79vvx8zhneWLsOcdBti /vT5vOdZKJndel926GduNNEBI0b4yt/VyEOv+oNBZDmdZZHRAe0lWV7MoMIkJUH71Y YJ5YUnvafWnMJpU8TCmbEQguN6pCHXUYQRb5LGiO9E80bB5pQ4pU5/Aa9QJ3uDq09b ygzDjga+86edw== Date: Mon, 9 Oct 2023 12:09:51 +0300 From: Mike Rapoport To: Axel Rasmussen Cc: Alejandro Colomar , Peter Xu , linux-man@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 10/10] ioctl_userfaultfd.2: document new UFFDIO_POISON ioctl Message-ID: <20231009090951.GM3303@kernel.org> References: <20230919190206.388896-1-axelrasmussen@google.com> <20230919190206.388896-11-axelrasmussen@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230919190206.388896-11-axelrasmussen@google.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Sep 19, 2023 at 12:02:06PM -0700, Axel Rasmussen wrote: > This is a new feature recently added to the kernel. So, document the new > ioctl the same way we do other UFFDIO_* ioctls. > > Also note the corresponding new ioctl flag we can return in reponse to a > UFFDIO_REGISTER call. > > Signed-off-by: Axel Rasmussen With a small correction Reviewed-by: Mike Rapoport (IBM) > --- > man2/ioctl_userfaultfd.2 | 112 +++++++++++++++++++++++++++++++++++++++ > 1 file changed, 112 insertions(+) > > diff --git a/man2/ioctl_userfaultfd.2 b/man2/ioctl_userfaultfd.2 > index afe3caffc..1282f63e1 100644 > --- a/man2/ioctl_userfaultfd.2 > +++ b/man2/ioctl_userfaultfd.2 > @@ -405,6 +405,11 @@ operation is supported. > The > .B UFFDIO_CONTINUE > operation is supported. > +.TP > +.B 1 << _UFFDIO_POISON > +The > +.B UFFDIO_POISON > +operation is supported. > .PP > This > .BR ioctl (2) > @@ -916,6 +921,113 @@ The faulting process has exited at the time of a > .B UFFDIO_CONTINUE > operation. > .\" > +.SS UFFDIO_POISON > +(Since Linux 6.6.) > +Mark an address range as "poisoned". > +Future accesses to these addresses will raise a > +.B SIGBUS > +signal. > +Unlike > +.B MADV_HWPOISON > +this works by installing page table entries, > +rather than "really" poisoning the underlying physical pages. > +This means it only affects this particular address space. > +.PP > +The > +.I argp > +argument is a pointer to a > +.I uffdio_continue Did you mean uffdio_poison? > +structure as shown below: > +.PP > +.in +4n > +.EX > +struct uffdio_poison { > + struct uffdio_range range; > + /* Range to install poison PTE markers in */ > + __u64 mode; /* Flags controlling the behavior of poison */ > + __s64 updated; /* Number of bytes poisoned, or negated error */ > +}; > +.EE > +.in > +.PP > +The following value may be bitwise ORed in > +.I mode > +to change the behavior of the > +.B UFFDIO_POISON > +operation: > +.TP > +.B UFFDIO_POISON_MODE_DONTWAKE > +Do not wake up the thread that waits for page-fault resolution. > +.PP > +The > +.I updated > +field is used by the kernel > +to return the number of bytes that were actually poisoned, > +or an error in the same manner as > +.BR UFFDIO_COPY . > +If the value returned in the > +.I updated > +field doesn't match the value that was specified in > +.IR range.len , > +the operation fails with the error > +.BR EAGAIN . > +The > +.I updated > +field is output-only; > +it is not read by the > +.B UFFDIO_POISON > +operation. > +.PP > +This > +.BR ioctl (2) > +operation returns 0 on success. > +In this case, > +the entire area was poisoned. > +On error, \-1 is returned and > +.I errno > +is set to indicate the error. > +Possible errors include: > +.TP > +.B EAGAIN > +The number of bytes mapped > +(i.e., the value returned in the > +.I updated > +field) > +does not equal the value that was specified in the > +.I range.len > +field. > +.TP > +.B EINVAL > +Either > +.I range.start > +or > +.I range.len > +was not a multiple of the system page size; or > +.I range.len > +was zero; or the range specified was invalid. > +.TP > +.B EINVAL > +An invalid bit was specified in the > +.I mode > +field. > +.TP > +.B EEXIST > +One or more pages were already mapped in the given range. > +.TP > +.B ENOENT > +The faulting process has changed its virtual memory layout simultaneously with > +an outstanding > +.B UFFDIO_POISON > +operation. > +.TP > +.B ENOMEM > +Allocating memory for page table entries failed. > +.TP > +.B ESRCH > +The faulting process has exited at the time of a > +.B UFFDIO_POISON > +operation. > +.\" > .SH RETURN VALUE > See descriptions of the individual operations, above. > .SH ERRORS > -- > 2.42.0.459.ge4e396fd5e-goog > > -- Sincerely yours, Mike.