From: Stoiko Ivanov <s.ivanov@proxmox.com>
To: Thomas Lamprecht <t.lamprecht@proxmox.com>
Cc: Proxmox VE development discussion <pve-devel@lists.proxmox.com>
Subject: Re: [pve-devel] [PATCH pve-kernel] d/rules: kconfig: do not enable intel_iommu by default
Date: Fri, 13 May 2022 12:03:14 +0200 [thread overview]
Message-ID: <20220513120314.2df86f9d@rosa.proxmox.com> (raw)
In-Reply-To: <4d537794-0ff8-5baf-513d-4dcdb3096d9a@proxmox.com>
On Fri, 13 May 2022 11:31:42 +0200
Thomas Lamprecht <t.lamprecht@proxmox.com> wrote:
> Am 5/13/22 um 10:57 schrieb Stoiko Ivanov:
> ..snip..
> > alternatively we could document this in the 7.2 release notes and ask
> > users of problematic hardware to set this explicitly
>
> This all resembles quite a bit the switch from nested KVM to be enabled,
> which we caught upfront and actively disabled to avoid trouble on migration
> due to QEMU not being yet ready for that change, and only enabled it in the
> next major release (6.0 IIRC) where we could be sure that a new enough QEMU
> is available.
>
> The difference here is that:
> * we may never be sure that all setups out there support IOMMU, at least not
> if we don't get another major divider like the switch from 32bit to 64bit
> was
agreed - I think we want to switch to default enabled eventually - my idea
was to have it even more visible during a major version-upgrade ...
OTOH since we just released 7.2 and have a known-issues section - I think
adding it there and linking to that should work fine.
>
> * we already switched it on now, sow disabling it may also break some setups
> that never did so manually.
my gut-feeling would be that most people who need it enabled (for
pci-passtrough) would follow the docs (of the past years) and set it
explicitly [0] - but you're right - it's a regression we would need to
document too.
> FWIW, we could also disable this dynamically with a modprobe cfg file that
> disables it if:
> - not manually enabled already (grep for that)
> - an older CPU (family) is present, where the cutoff would need to be
> decided
maybe I'm missing something - but intel_iommu is builtin (not a module) -
and options for those need to be provided on the kernel commandline [1]?
and while (semi-optionally) shipping a modprobe.conf snippet could work,
I wouldn't want to `sed` in our user's `/etc/default/grub`,
`/etc/kernel/cmdline` in a postinst.
we could add it to the NEWS file for the packages - to give it some
visibility though)?
[0] we should update our docs on pci-passthrough (mostly meant as note to
myself)
[1]
https://www.kernel.org/doc/html/v4.14/admin-guide/kernel-parameters.html
prev parent reply other threads:[~2022-05-13 10:03 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-05-13 8:57 Stoiko Ivanov
2022-05-13 9:31 ` Thomas Lamprecht
2022-05-13 10:03 ` Stoiko Ivanov [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=20220513120314.2df86f9d@rosa.proxmox.com \
--to=s.ivanov@proxmox.com \
--cc=pve-devel@lists.proxmox.com \
--cc=t.lamprecht@proxmox.com \
/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