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From: Jens Axboe <[email protected]>
To: Helge Deller <[email protected]>, [email protected]
Cc: John David Anglin <[email protected]>,
	linux-parisc <[email protected]>
Subject: Re: io_uring failure on parisc (32-bit userspace and 64-bit kernel)
Date: Mon, 13 Feb 2023 14:05:11 -0700	[thread overview]
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>

On 2/13/23 1:59?PM, Helge Deller wrote:
>> Yep sounds like it. What's the caching architecture of parisc?
> 
> parisc is Virtually Indexed, Physically Tagged (VIPT).

That's what I assumed, so virtual aliasing is what we're dealing with
here.

> Thanks for the patch!
> Sadly it doesn't fix the problem, as the kernel still sees
> ctx->rings->sq.tail as being 0.
> Interestingly it worked once (not reproduceable) directly after bootup,
> which indicates that we at least look at the right address from kernel side.
> 
> So, still needs more debugging/testing.

It's not like this is untested stuff, so yeah it'll generally be
correct, it just seems that parisc is a bit odd in that the virtual
aliasing occurs between the kernel and userspace addresses too. At least
that's what it seems like.

But I wonder if what needs flushing is the user side, not the kernel
side? Either that, or my patch is not flushing the right thing on the
kernel side.

Is it possible to flush it from the userspace side? Presumable that's
what we'd need on the sqe side, and then the kernel side for the cqe
filling. So probably the patch is half-way correct :-)

-- 
Jens Axboe


  reply	other threads:[~2023-02-13 21:05 UTC|newest]

Thread overview: 48+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-02-12  9:47 io_uring failure on parisc (32-bit userspace and 64-bit kernel) Helge Deller
2023-02-12 13:16 ` Jens Axboe
2023-02-12 13:28   ` Helge Deller
2023-02-12 13:35     ` Jens Axboe
2023-02-12 14:00       ` Jens Axboe
2023-02-12 14:03       ` Helge Deller
2023-02-12 19:35         ` Helge Deller
2023-02-12 19:42           ` Jens Axboe
2023-02-12 20:01             ` Helge Deller
2023-02-12 21:48               ` Jens Axboe
2023-02-12 22:20                 ` Helge Deller
2023-02-12 22:31                   ` Helge Deller
2023-02-13 16:15                     ` Jens Axboe
2023-02-13 20:59                       ` Helge Deller
2023-02-13 21:05                         ` Jens Axboe [this message]
2023-02-13 22:05                           ` Helge Deller
2023-02-13 22:50                             ` John David Anglin
2023-02-14 23:09                               ` io_uring failure on parisc with VIPT caches Helge Deller
2023-02-14 23:29                                 ` Jens Axboe
2023-02-15  2:12                                   ` John David Anglin
2023-02-15 15:16                                     ` Jens Axboe
2023-02-15 15:52                                       ` Helge Deller
2023-02-15 15:56                                         ` Jens Axboe
2023-02-15 16:02                                           ` Helge Deller
2023-02-15 16:04                                             ` Jens Axboe
2023-02-15 21:40                                               ` Helge Deller
2023-02-15 23:04                                                 ` Jens Axboe
2023-02-15 16:38                                           ` John David Anglin
2023-02-15 17:01                                             ` Jens Axboe
2023-02-15 19:00                                               ` Jens Axboe
2023-02-15 19:16                                                 ` Jens Axboe
2023-02-15 20:27                                                   ` John David Anglin
2023-02-15 20:37                                                     ` Jens Axboe
2023-02-15 21:06                                                       ` John David Anglin
2023-02-15 21:38                                                         ` Jens Axboe
2023-02-15 21:39                                                         ` John David Anglin
2023-02-15 22:10                                                           ` John David Anglin
2023-02-15 23:02                                                             ` Jens Axboe
2023-02-15 23:43                                                               ` John David Anglin
2023-02-16  2:40                                                               ` John David Anglin
2023-02-16  2:50                                                                 ` Jens Axboe
2023-02-16  8:24                                                                   ` Helge Deller
2023-02-16 15:22                                                                     ` Jens Axboe
2023-02-16 20:35                                                                     ` John David Anglin
2023-02-15 23:03                                                           ` Jens Axboe
2023-02-15 19:20                                                 ` John David Anglin
2023-02-15 19:24                                                   ` Jens Axboe
2023-02-15 16:18                                         ` John David Anglin

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