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Date: Mon, 21 Sep 2026 12:42:22 +0100
From: "Lorenzo Stoakes (ARM)" <ljs@kernel.org>
To: Fuad Tabba <fuad.tabba@linux.dev>
Cc: Oliver Upton <oupton@kernel.org>, Marc Zyngier <maz@kernel.org>, 
	Joey Gouly <joey.gouly@arm.com>, Steffen Eiden <seiden@linux.ibm.com>, 
	Suzuki K Poulose <suzuki.poulose@arm.com>, Zenghui Yu <yuzenghui@huawei.com>, Will Deacon <will@kernel.org>, 
	Jack Thomson <jackabt@amazon.com>, kvmarm@lists.linux.dev, linux-arm-kernel@lists.infradead.org, 
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2] KVM: arm64: Restore the VM's feature bitmap when
 kvm_setup_vcpu() fails
Message-ID: <arEWo3yDYkWp55sF@gremlin>
References: <20260921063718.1604533-1-fuad.tabba@linux.dev>
 <arDYHSlFHm_XzGvN@kernel.org>
 <CA+EHjTz0-qS8RRhdT8XjAgWqKhgjjzbRsZ_jwTBVqM-8pXk7Vw@mail.gmail.com>
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On Mon, Sep 21, 2026 at 08:24:56AM +0100, Fuad Tabba wrote:
> Hi Oliver,
>
> On Mon, 21 Sep 2026 00:09:17 -0700, Oliver Upton <oupton@kernel.org> wrote:
> [...]
> > > Nothing in the tree loads a vCPU whose init failed, so this is latent.
> > > The upcoming series that enables KVM_PRE_FAULT_MEMORY for arm64 exposes
> > > it: the generic kvm_vcpu_pre_fault_memory() calls vcpu_load() whether
> > > or not the vCPU has been initialised.
> >
> > That's a bug, not a feature. We should require an initialized vcpu for
> > the ioctl.
>
> That one is for Lorenzo then :) I'll reword the message so the stale
> bitmap comes first and the pre-fault crash is just how it showed up.

Let me dig into this.

--
Cheers, Lorenzo