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From: Oliver Upton <oliver.upton@linux.dev>
To: Marc Zyngier <maz@kernel.org>
Cc: Eric Auger <eauger@redhat.com>,
	Ganapatrao Kulkarni <gankulkarni@os.amperecomputing.com>,
	kvmarm <kvmarm@lists.linux.dev>,
	linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org, christoffer.dall@arm.com,
	suzuki.poulose@arm.com, will@kernel.org, catalin.marinas@arm.com,
	coltonlewis@google.com, joey.gouly@arm.com, yuzenghui@huawei.com,
	darren@os.amperecomputing.com, vishnu@os.amperecomputing.com
Subject: Re: [PATCH] KVM: arm64: nv: Set ISTATUS for emulated timers, If timer expired
Date: Fri, 7 Feb 2025 10:09:58 -0800	[thread overview]
Message-ID: <Z6ZMdv8jJUvYwQzT@linux.dev> (raw)
In-Reply-To: <86frkptzr6.wl-maz@kernel.org>

Hey,

On Fri, Feb 07, 2025 at 05:45:33PM +0000, Marc Zyngier wrote:
> I found at least one issue that could fail the migration. Before the
> VM starts running, we limit the feature set to the subset we actually
> support with NV.
> 
> By doing this, we also change the value of IDreg fields that are not
> writable, because they describe features that we don't support.
> Obviously, that fails on restore.
> 
> I need to have a think...

We spoke about this a while ago (and I forgot til now), but I was
wondering if we could use vCPU feature flags to describe NV, including
the selection between FEAT_E2H0 and FEAT_VHE.

I think this might match userspace expectations a bit more closely where
the state of the ID registers after init gives the actual feature set
supported by the VM.

-- 
Thanks,
Oliver


  reply	other threads:[~2025-02-07 18:13 UTC|newest]

Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-12-09  5:32 [PATCH] KVM: arm64: nv: Set ISTATUS for emulated timers, If timer expired Ganapatrao Kulkarni
2024-12-09  9:54 ` Marc Zyngier
2024-12-09 12:25   ` Ganapatrao Kulkarni
2024-12-09 13:20     ` Marc Zyngier
2024-12-09 15:23       ` Marc Zyngier
2024-12-09 15:39       ` Ganapatrao Kulkarni
2024-12-09 15:52         ` Marc Zyngier
2024-12-09 16:46         ` Eric Auger
2024-12-09 17:30           ` Marc Zyngier
2024-12-09 17:34             ` Eric Auger
2024-12-19  9:30               ` Ganapatrao Kulkarni
2024-12-19 12:23                 ` Marc Zyngier
2025-01-14 13:12                 ` Eric Auger
2025-01-14 14:38                   ` Marc Zyngier
2025-01-14 14:57                     ` Eric Auger
2025-01-14 15:52                       ` Marc Zyngier
2025-01-16 17:52                         ` Eric Auger
2025-01-16 18:25                           ` Marc Zyngier
2025-02-07 17:45                           ` Marc Zyngier
2025-02-07 18:09                             ` Oliver Upton [this message]
2025-02-07 18:38                               ` Marc Zyngier
2025-02-07 19:08                                 ` Oliver Upton
2025-02-10 18:26                                 ` Eric Auger
2025-02-11 19:20                                   ` Marc Zyngier
2025-02-15 17:50                                   ` Marc Zyngier
2025-02-18  7:33                                     ` Ganapatrao Kulkarni
2025-02-18 16:33                                       ` Marc Zyngier
2025-02-18 21:24                                       ` Marc Zyngier
2025-02-20  6:10                                         ` Ganapatrao Kulkarni
2025-02-10 13:18                             ` Eric Auger
2024-12-10 12:48       ` Ganapatrao Kulkarni
2024-12-09 19:36 ` kernel test robot

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