From: Marc Zyngier <maz@kernel.org>
To: Alexandru Elisei <alexandru.elisei@arm.com>
Cc: kvm@vger.kernel.org, will@kernel.org,
kvmarm@lists.cs.columbia.edu,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v2 0/2] KVM: arm64: Uphold 64bit-only behavior on asymmetric systems
Date: Wed, 17 Aug 2022 11:56:50 +0100 [thread overview]
Message-ID: <87sflvw32l.wl-maz@kernel.org> (raw)
In-Reply-To: <YvzIVo5H21upnaPt@monolith.localdoman>
On Wed, 17 Aug 2022 11:52:06 +0100,
Alexandru Elisei <alexandru.elisei@arm.com> wrote:
>
> Hi,
>
> On Wed, Aug 17, 2022 at 11:07:10AM +0100, Marc Zyngier wrote:
> > On Tue, 16 Aug 2022 20:25:52 +0100,
> > Oliver Upton <oliver.upton@linux.dev> wrote:
> > >
> > > Small series to fix a couple issues around when 64bit-only behavior is
> > > applied. As KVM is more restrictive than the kernel in terms of 32bit
> > > support (no asymmetry), we really needed our own predicate when the
> > > meaning of system_supports_32bit_el0() changed in commit 2122a833316f
> > > ("arm64: Allow mismatched 32-bit EL0 support").
> > >
> > > Lightly tested as I do not have any asymmetric systems on hand at the
> > > moment. Attention on patch 2 would be appreciated as it affects ABI.
> >
> > I don't think this significantly affect the ABI, as it is pretty
> > unlikely that you'd have been able to execute the result, at least on
> > VM creation (set PSTATE.M=USR, start executing, get the page fault on
> > the first instruction... bang).
> >
> > You could have tricked it in other ways, but at the end of the day
> > you're running a broken hypervisor on an even more broken system...
>
> Just FYI, you can create such a system on models, by running two clusters
> and setting clusterX.max_32bit_el=-1. Or you can have even crazier
> configurations, where AArch32 support is present on only one cluster, and
> only for EL0.
You mean, just as crazy as some of the systems out there? :D
Thanks,
M.
--
Without deviation from the norm, progress is not possible.
_______________________________________________
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kvmarm@lists.cs.columbia.edu
https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
WARNING: multiple messages have this Message-ID (diff)
From: Marc Zyngier <maz@kernel.org>
To: Alexandru Elisei <alexandru.elisei@arm.com>
Cc: Oliver Upton <oliver.upton@linux.dev>,
kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org,
linux-arm-kernel@lists.infradead.org, james.morse@arm.com,
suzuki.poulose@arm.com, will@kernel.org
Subject: Re: [PATCH v2 0/2] KVM: arm64: Uphold 64bit-only behavior on asymmetric systems
Date: Wed, 17 Aug 2022 11:56:50 +0100 [thread overview]
Message-ID: <87sflvw32l.wl-maz@kernel.org> (raw)
In-Reply-To: <YvzIVo5H21upnaPt@monolith.localdoman>
On Wed, 17 Aug 2022 11:52:06 +0100,
Alexandru Elisei <alexandru.elisei@arm.com> wrote:
>
> Hi,
>
> On Wed, Aug 17, 2022 at 11:07:10AM +0100, Marc Zyngier wrote:
> > On Tue, 16 Aug 2022 20:25:52 +0100,
> > Oliver Upton <oliver.upton@linux.dev> wrote:
> > >
> > > Small series to fix a couple issues around when 64bit-only behavior is
> > > applied. As KVM is more restrictive than the kernel in terms of 32bit
> > > support (no asymmetry), we really needed our own predicate when the
> > > meaning of system_supports_32bit_el0() changed in commit 2122a833316f
> > > ("arm64: Allow mismatched 32-bit EL0 support").
> > >
> > > Lightly tested as I do not have any asymmetric systems on hand at the
> > > moment. Attention on patch 2 would be appreciated as it affects ABI.
> >
> > I don't think this significantly affect the ABI, as it is pretty
> > unlikely that you'd have been able to execute the result, at least on
> > VM creation (set PSTATE.M=USR, start executing, get the page fault on
> > the first instruction... bang).
> >
> > You could have tricked it in other ways, but at the end of the day
> > you're running a broken hypervisor on an even more broken system...
>
> Just FYI, you can create such a system on models, by running two clusters
> and setting clusterX.max_32bit_el=-1. Or you can have even crazier
> configurations, where AArch32 support is present on only one cluster, and
> only for EL0.
You mean, just as crazy as some of the systems out there? :D
Thanks,
M.
--
Without deviation from the norm, progress is not possible.
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
WARNING: multiple messages have this Message-ID (diff)
From: Marc Zyngier <maz@kernel.org>
To: Alexandru Elisei <alexandru.elisei@arm.com>
Cc: Oliver Upton <oliver.upton@linux.dev>,
kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org,
linux-arm-kernel@lists.infradead.org, james.morse@arm.com,
suzuki.poulose@arm.com, will@kernel.org
Subject: Re: [PATCH v2 0/2] KVM: arm64: Uphold 64bit-only behavior on asymmetric systems
Date: Wed, 17 Aug 2022 11:56:50 +0100 [thread overview]
Message-ID: <87sflvw32l.wl-maz@kernel.org> (raw)
In-Reply-To: <YvzIVo5H21upnaPt@monolith.localdoman>
On Wed, 17 Aug 2022 11:52:06 +0100,
Alexandru Elisei <alexandru.elisei@arm.com> wrote:
>
> Hi,
>
> On Wed, Aug 17, 2022 at 11:07:10AM +0100, Marc Zyngier wrote:
> > On Tue, 16 Aug 2022 20:25:52 +0100,
> > Oliver Upton <oliver.upton@linux.dev> wrote:
> > >
> > > Small series to fix a couple issues around when 64bit-only behavior is
> > > applied. As KVM is more restrictive than the kernel in terms of 32bit
> > > support (no asymmetry), we really needed our own predicate when the
> > > meaning of system_supports_32bit_el0() changed in commit 2122a833316f
> > > ("arm64: Allow mismatched 32-bit EL0 support").
> > >
> > > Lightly tested as I do not have any asymmetric systems on hand at the
> > > moment. Attention on patch 2 would be appreciated as it affects ABI.
> >
> > I don't think this significantly affect the ABI, as it is pretty
> > unlikely that you'd have been able to execute the result, at least on
> > VM creation (set PSTATE.M=USR, start executing, get the page fault on
> > the first instruction... bang).
> >
> > You could have tricked it in other ways, but at the end of the day
> > you're running a broken hypervisor on an even more broken system...
>
> Just FYI, you can create such a system on models, by running two clusters
> and setting clusterX.max_32bit_el=-1. Or you can have even crazier
> configurations, where AArch32 support is present on only one cluster, and
> only for EL0.
You mean, just as crazy as some of the systems out there? :D
Thanks,
M.
--
Without deviation from the norm, progress is not possible.
next prev parent reply other threads:[~2022-08-17 10:56 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-08-16 19:25 [PATCH v2 0/2] KVM: arm64: Uphold 64bit-only behavior on asymmetric systems Oliver Upton
2022-08-16 19:25 ` Oliver Upton
2022-08-16 19:25 ` Oliver Upton
2022-08-16 19:25 ` [PATCH v2 1/2] KVM: arm64: Treat PMCR_EL1.LC as RES1 " Oliver Upton
2022-08-16 19:25 ` Oliver Upton
2022-08-16 19:25 ` Oliver Upton
2022-08-16 19:25 ` [PATCH v2 2/2] KVM: arm64: Reject 32bit user PSTATE " Oliver Upton
2022-08-16 19:25 ` Oliver Upton
2022-08-16 19:25 ` Oliver Upton
2022-08-17 9:33 ` [PATCH v2 0/2] KVM: arm64: Uphold 64bit-only behavior " Marc Zyngier
2022-08-17 9:33 ` Marc Zyngier
2022-08-17 9:33 ` Marc Zyngier
2022-08-17 10:07 ` Marc Zyngier
2022-08-17 10:07 ` Marc Zyngier
2022-08-17 10:07 ` Marc Zyngier
2022-08-17 10:52 ` Alexandru Elisei
2022-08-17 10:52 ` Alexandru Elisei
2022-08-17 10:52 ` Alexandru Elisei
2022-08-17 10:56 ` Marc Zyngier [this message]
2022-08-17 10:56 ` Marc Zyngier
2022-08-17 10:56 ` Marc Zyngier
2022-08-17 15:13 ` Oliver Upton
2022-08-17 15:13 ` Oliver Upton
2022-08-17 15:13 ` Oliver Upton
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