From: Maxim Levitsky <mlevitsk@redhat.com>
To: Thomas Huth <thuth@redhat.com>, Sean Christopherson <seanjc@google.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>,
linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
"Daniel P. Berrange" <berrange@redhat.com>
Subject: Re: [PATCH] KVM: x86: disable on 32-bit unless CONFIG_BROKEN
Date: Thu, 23 Feb 2023 10:33:08 +0200 [thread overview]
Message-ID: <092591cbcc40fbbcc42abd3f603b6d782f411770.camel@redhat.com> (raw)
In-Reply-To: <05144c6d-922c-e70d-e625-c60952b60f3c@redhat.com>
On Thu, 2023-02-23 at 08:01 +0100, Thomas Huth wrote:
> On 22/02/2023 23.27, Sean Christopherson wrote:
> > On Fri, Feb 17, 2023, Thomas Huth wrote:
> > > On 29/09/2022 15.52, Maxim Levitsky wrote:
> > > > On Thu, 2022-09-29 at 15:26 +0200, Paolo Bonzini wrote:
> > > > > On 9/28/22 19:55, Sean Christopherson wrote:
> > > > > > > As far as my opinion goes I do volunteer to test this code more often,
> > > > > > > and I do not want to see the 32 bit KVM support be removed*yet*.
> > > > > >
> > > > > > Yeah, I 100% agree that it shouldn't be removed until we have equivalent test
> > > > > > coverage. But I do think it should an "off-by-default" sort of thing. Maybe
> > > > > > BROKEN is the wrong dependency though? E.g. would EXPERT be a better option?
> > > > >
> > > > > Yeah, maybe EXPERT is better but I'm not sure of the equivalent test
> > > > > coverage. 32-bit VMX/SVM kvm-unit-tests are surely a good idea, but
> > > > > what's wrong with booting an older guest?
> > > > > From my point of view, using the same kernel source for host and the guest
> > > > is easier because you know that both kernels behave the same.
> > > >
> > > > About EXPERT, IMHO these days most distros already dropped 32 bit suport thus anyway
> > > > one needs to compile a recent 32 bit kernel manually - thus IMHO whoever
> > > > these days compiles a 32 bit kernel, knows what they are doing.
> > > >
> > > > I personally would wait few more releases when there is a pressing reason to remove
> > > > this support.
> > >
> > > FWIW, from the QEMU perspective, it would be very helpful to remove 32-bit
> > > KVM support from the kernel. The QEMU project currently struggles badly with
> > > keeping everything tested in the CI in a reasonable amount of time. The
> > > 32-bit KVM kernel support is the only reason to keep the qemu-system-i386
> > > binary around - everything else can be covered with the qemu-system-x86_64
> > > binary that is a superset of the -i386 variant (except for the KVM part as
> > > far as I know).
> > > Sure, we could also drop qemu-system-i386 from the CI without dropping the
> > > 32-bit KVM code in the kernel, but I guess things will rather bitrot there
> > > even faster in that case, so I'd appreciate if the kernel could drop the
> > > 32-bit in the near future, too.
> >
> > Ya, I would happily drop support for 32-bit kernels today, the only sticking point
> > is the lack of 32-bit shadow paging test coverage, which unfortunately is a rather
> > large point. :-(
>
> From your point of view, would it be OK if QEMU dropped qemu-system-i386?
> I.e. would it be fine to use older versions of QEMU only for that test
> coverage (or do you even use a different userspace for testing that)?
>
> Thomas
>
From my point of view qemu-system-x86_64 does run 32 bit guests just fine.
The only exception that I know is that gdbstub is somewhat broken, but that can be probably
fixed.
Best regards,
Maxim Levitsky
next prev parent reply other threads:[~2023-02-23 8:35 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-26 16:51 [PATCH] KVM: x86: disable on 32-bit unless CONFIG_BROKEN Paolo Bonzini
2022-09-27 17:07 ` Sean Christopherson
2022-09-28 7:10 ` Maxim Levitsky
2022-09-28 9:55 ` Paolo Bonzini
2022-09-28 16:12 ` Sean Christopherson
2022-09-28 17:43 ` Maxim Levitsky
2022-09-28 17:44 ` Maxim Levitsky
2022-09-28 17:55 ` Sean Christopherson
2022-09-29 13:26 ` Paolo Bonzini
2022-09-29 13:52 ` Maxim Levitsky
2022-09-29 15:07 ` Paolo Bonzini
2023-02-17 19:36 ` Thomas Huth
2023-02-22 22:27 ` Sean Christopherson
2023-02-23 7:01 ` Thomas Huth
2023-02-23 8:33 ` Maxim Levitsky [this message]
2023-02-23 22:10 ` Sean Christopherson
2023-02-24 6:28 ` Thomas Huth
2022-09-28 10:04 ` Paolo Bonzini
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