From: Will Deacon <will@kernel.org>
To: Marc Zyngier <maz@kernel.org>
Cc: kvm@vger.kernel.org, kvmarm@lists.cs.columbia.edu,
linux-arm-kernel@lists.infradead.org,
Peng Liang <liangpeng10@huawei.com>,
James Morse <james.morse@arm.com>,
Julien Thierry <julien.thierry.kdev@gmail.com>,
Suzuki K Poulose <suzuki.poulose@arm.com>,
kernel-team@android.com
Subject: Re: [PATCH v2 1/3] KVM: arm64: Allow setting of ID_AA64PFR0_EL1.CSV2 from userspace
Date: Wed, 11 Nov 2020 22:01:06 +0000 [thread overview]
Message-ID: <20201111220105.GA18414@willie-the-truck> (raw)
In-Reply-To: <20201110141308.451654-2-maz@kernel.org>
On Tue, Nov 10, 2020 at 02:13:06PM +0000, Marc Zyngier wrote:
> We now expose ID_AA64PFR0_EL1.CSV2=1 to guests running on hosts
> that are immune to Spectre-v2, but that don't have this field set,
> most likely because they predate the specification.
>
> However, this prevents the migration of guests that have started on
> a host the doesn't fake this CSV2 setting to one that does, as KVM
> rejects the write to ID_AA64PFR0_EL2 on the grounds that it isn't
> what is already there.
>
> In order to fix this, allow userspace to set this field as long as
> this doesn't result in a promising more than what is already there
> (setting CSV2 to 0 is acceptable, but setting it to 1 when it is
> already set to 0 isn't).
>
> Fixes: e1026237f9067 ("KVM: arm64: Set CSV2 for guests on hardware unaffected by Spectre-v2")
> Reported-by: Peng Liang <liangpeng10@huawei.com>
> Signed-off-by: Marc Zyngier <maz@kernel.org>
> ---
> arch/arm64/include/asm/kvm_host.h | 2 ++
> arch/arm64/kvm/arm.c | 16 ++++++++++++
> arch/arm64/kvm/sys_regs.c | 42 ++++++++++++++++++++++++++++---
> 3 files changed, 56 insertions(+), 4 deletions(-)
Acked-by: Will Deacon <will@kernel.org>
Will
next prev parent reply other threads:[~2020-11-11 22:01 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-10 14:13 [PATCH v2 0/3] KVM: arm64: Another set of CSV2-related fixes Marc Zyngier
2020-11-10 14:13 ` [PATCH v2 1/3] KVM: arm64: Allow setting of ID_AA64PFR0_EL1.CSV2 from userspace Marc Zyngier
2020-11-11 22:01 ` Will Deacon [this message]
2020-11-10 14:13 ` [PATCH v2 2/3] KVM: arm64: Unify trap handlers injecting an UNDEF Marc Zyngier
2020-11-11 22:01 ` Will Deacon
2020-11-10 14:13 ` [PATCH v2 3/3] KVM: arm64: Handle SCXTNUM_ELx traps Marc Zyngier
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