From: Marc Zyngier <maz@kernel.org>
To: Ganapatrao Kulkarni <gankulkarni@os.amperecomputing.com>
Cc: linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev,
linux-kernel@vger.kernel.org, oliver.upton@linux.dev,
joey.gouly@arm.com, suzuki.poulose@arm.com, yuzenghui@huawei.com,
darren@os.amperecomputing.com
Subject: Re: [PATCH] KVM: arm64: nv: Forward hvc traps if originated from nested VM
Date: Thu, 10 Apr 2025 08:19:16 +0100 [thread overview]
Message-ID: <86mscolc0b.wl-maz@kernel.org> (raw)
In-Reply-To: <20250410070743.1072583-1-gankulkarni@os.amperecomputing.com>
On Thu, 10 Apr 2025 08:07:43 +0100,
Ganapatrao Kulkarni <gankulkarni@os.amperecomputing.com> wrote:
>
> It was discovered while trying selftest(smccc_filter) that the
> hvc trap is getting forwarded to guest hypervisor even if it is
> originated from itself.
>
> HVC traps from guest hypervisor should be handled by the host
> hypervisor and traps originating from nested VM should be
> forwarded. Adding check to forward only if the hvc is trapped
> from the nested VM.
I disagree. HVC from EL2 must be routed to the same EL2. HVC from EL1
must be routed to the EL2 controlling EL1.
In no circumstances should HVC from a NV guest be directly handled by
the host hypervisor. That's what SMC is for.
Please read the pseudocode for HVC.
M.
--
Without deviation from the norm, progress is not possible.
next prev parent reply other threads:[~2025-04-10 7:19 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-04-10 7:07 [PATCH] KVM: arm64: nv: Forward hvc traps if originated from nested VM Ganapatrao Kulkarni
2025-04-10 7:19 ` Marc Zyngier [this message]
2025-04-10 10:20 ` Ganapatrao Kulkarni
2025-04-10 10:52 ` Marc Zyngier
2025-04-10 13:22 ` Ganapatrao Kulkarni
2025-04-10 17:31 ` Oliver Upton
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