From: Peter Maydell <peter.maydell@linaro.org>
To: Stefan Hajnoczi <stefanha@gmail.com>
Cc: "Fernando Casas Schössow" <casasfernando@outlook.com>,
"Paolo Bonzini" <pbonzini@redhat.com>,
"Richard Henderson" <rth@twiddle.net>,
qemu-devel <qemu-devel@nongnu.org>,
"Natanael Copa" <ncopa@alpinelinux.org>
Subject: Re: [Qemu-devel] [Qemu-block] Guest unresponsive after Virtqueue size exceeded error
Date: Sat, 23 Feb 2019 16:57:23 +0000 [thread overview]
Message-ID: <CAFEAcA9xXoM-Bh=oAwX5KOaNoRo1vg_oYV+o6WpPTOVPFC=8Ew@mail.gmail.com> (raw)
In-Reply-To: <CAJSP0QWouR43wVi0guTuASP9gc24_CPucbBvtfE5_htkDkmsrQ@mail.gmail.com>
On Fri, 22 Feb 2019 at 14:07, Stefan Hajnoczi <stefanha@gmail.com> wrote:
> Richard: Commit 7db2145a6826b14efceb8dd64bfe6ad8647072eb ("bswap: Add
> host endian unaligned access functions") introduced the unaligned
> memory access functions in question here. Please see below for
> details on the bug - basically QEMU code assumes they are atomic, but
> that is not guaranteed :(. Any ideas for how to fix this?
I suspect we want a separate family of access functions for
"I guarantee this will be an aligned access and I need the
atomicity". (The other place where we've talked about needing
the atomicity is in emulation of page-table-walk, where you
need the page table loads to be atomic w.r.t. other CPU
threads, especially in the case where you need to emulate
a hardware update of a dirty/access bit in the page table entry.)
Mostly this hasn't bitten us before because any sensible compiler
will turn the memcpy into a straight load on most common hosts,
which will be atomic (but accidentally rather than on purpose).
thanks
-- PMM
prev parent reply other threads:[~2019-02-23 16:58 UTC|newest]
Thread overview: 55+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-06-14 21:56 [Qemu-devel] Guest unresponsive after Virtqueue size exceeded error Fernando Casas Schössow
2017-06-16 6:58 ` Ladi Prosek
2017-06-16 10:11 ` Fernando Casas Schössow
2017-06-16 10:25 ` Ladi Prosek
2017-06-19 22:10 ` Fernando Casas Schössow
2017-06-20 5:59 ` Ladi Prosek
2017-06-20 6:30 ` Fernando Casas Schössow
2017-06-20 7:52 ` Ladi Prosek
2017-06-21 12:19 ` Fernando Casas Schössow
2017-06-22 7:43 ` Ladi Prosek
2017-06-23 6:29 ` Fernando Casas Schössow
[not found] ` <1498199343.2815.0@smtp-mail.outlook.com>
2017-06-24 8:34 ` Fernando Casas Schössow
2019-01-31 11:32 ` Fernando Casas Schössow
2019-02-01 5:48 ` [Qemu-devel] [Qemu-block] " Stefan Hajnoczi
2019-02-01 8:17 ` Fernando Casas Schössow
2019-02-04 6:06 ` Stefan Hajnoczi
2019-02-04 7:24 ` Fernando Casas Schössow
[not found] ` <AM5PR0602MB32368CB5ADDEC05F42D8BC8FA46D0@AM5PR0602MB3236.eurprd06.prod.outlo ok.com>
2019-02-06 7:15 ` Fernando Casas Schössow
[not found] ` <AM5PR0602MB32368CB5ADDEC05F42D8BC8FA46D0@AM5PR0602MB3236.eurprd06.prod.outlo>
[not found] ` <VI1PR0602MB3245032D51A5DF45AF6E1952A46F0@VI1PR0602MB3245.eurprd06.prod.outlo ok.com>
2019-02-06 16:47 ` Fernando Casas Schössow
2019-02-11 3:17 ` Stefan Hajnoczi
2019-02-11 9:48 ` Fernando Casas Schössow
2019-02-18 7:21 ` Fernando Casas Schössow
[not found] ` <VI1PR0602MB3245424120D151F29884A7E2A4630@VI1PR0602MB3245.eurprd06.prod.outlo ok.com>
2019-02-19 7:26 ` Fernando Casas Schössow
2019-02-20 16:58 ` Stefan Hajnoczi
2019-02-20 17:53 ` Paolo Bonzini
2019-02-20 18:56 ` Fernando Casas Schössow
2019-02-21 11:11 ` Stefan Hajnoczi
2019-02-21 11:33 ` Fernando Casas Schössow
[not found] ` <VI1PR0602MB3245593855B029B427ED544FA47E0@VI1PR0602MB3245.eurprd06.prod.outlook.com>
[not found] ` <CAJSP0QUs9Yz2-k1KyVMwpgx6RwY9cK7qdQRCQ74xmgXJPJR-qw@mail.gmail.com>
[not found] ` <VI1PR0602MB32453A8B5CBC0308C7D18F1DA47E0@VI1PR0602MB3245.eurprd06.prod.outlook.com>
[not found] ` <CAJSP0QVxaW3tezjBN9owJHsxzE9h8_qcaeRr5zHHKxKJOeFnkQ@mail.gmail.com>
[not found] ` <CAJSP0QVXoZJ9MJ0qp4RM_m2fGJ8iFSyJMAU_X7mdiQvpOK59KA@mail.gmail.com>
[not found] ` <VI1PR0602MB324516419266A934FE7759C6A47E0@VI1PR0602MB3245.eurprd06.prod.outlook.com>
[not found] ` <VI1PR0602MB324516419266A934FE7759C6A47E0@VI1PR0602MB3245.eurprd06.prod.outlo>
[not found] ` <VI1PR0602MB32454C17192EFA863E29CC49A47E0@VI1PR0602MB3245.eurprd06.prod.outlo>
[not found] ` <VI1PR0602MB324547F72DA9EDEB1613C888A47E0@VI1PR0602MB3245.eurprd06.prod.outlook.com>
[not found] ` <CAJSP0QUg=cq3tCSLidQ9BR2hxAo3K6gA6LKtpx5Rjb=_6XgJ6Q@mail.gmail.com>
[not found] ` <28e6b4ed-9afd-3a79-6267-86c7385c23ce@redhat.com>
[not found] ` <VI1PR0602MB324578F91F1AF9390D03022FA47F0@VI1PR0602MB3245.eurprd06.prod.outlook.com>
2019-02-22 14:04 ` Stefan Hajnoczi
2019-02-22 14:38 ` Paolo Bonzini
2019-02-22 14:43 ` Fernando Casas Schössow
2019-02-22 14:55 ` Paolo Bonzini
2019-02-22 15:48 ` Fernando Casas Schössow
2019-02-22 16:37 ` Dr. David Alan Gilbert
2019-02-22 16:39 ` Paolo Bonzini
2019-02-22 16:47 ` Dr. David Alan Gilbert
2019-02-23 11:49 ` Natanael Copa
2019-02-26 13:30 ` Paolo Bonzini
2019-02-28 7:35 ` Fernando Casas Schössow
2019-02-23 15:55 ` Natanael Copa
2019-02-23 16:18 ` Peter Maydell
2019-02-25 10:24 ` Natanael Copa
2019-02-25 10:34 ` Peter Maydell
2019-02-25 12:15 ` Fernando Casas Schössow
2019-02-25 12:21 ` Natanael Copa
2019-02-25 13:06 ` Peter Maydell
2019-02-25 13:25 ` Natanael Copa
2019-02-25 13:32 ` Fernando Casas Schössow
[not found] ` <VI1PR0602MB3245A6B693B23DA2E0E8E500A47A0@VI1PR0602MB3245.eurprd06.prod.outlo ok.com>
2019-02-25 15:41 ` Fernando Casas Schössow
2019-02-28 9:58 ` Peter Maydell
2019-03-07 7:14 ` Fernando Casas Schössow
2019-02-23 16:21 ` Fernando Casas Schössow
2019-02-25 10:30 ` Stefan Hajnoczi
2019-02-25 10:33 ` Stefan Hajnoczi
2019-02-23 16:57 ` Peter Maydell [this message]
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