Re: [PATCH 0/2] KVM: arm64: Fixes for SMC64 SYSTEM_RESET2 calls

From: Will Deacon <will@kernel.org>
To: Oliver Upton <oupton@google.com>
Cc: kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org,
	Marc Zyngier <maz@kernel.org>, James Morse <james.morse@arm.com>,
	Alexandru Elisei <alexandru.elisei@arm.com>,
	Suzuki K Poulose <suzuki.poulose@arm.com>,
	linux-arm-kernel@lists.infradead.org,
	Peter Shier <pshier@google.com>,
	Ricardo Koller <ricarkol@google.com>,
	Reiji Watanabe <reijiw@google.com>,
	Paolo Bonzini <pbonzini@redhat.com>
Subject: Re: [PATCH 0/2] KVM: arm64: Fixes for SMC64 SYSTEM_RESET2 calls
Date: Mon, 21 Mar 2022 14:29:19 +0000	[thread overview]
Message-ID: <20220321142918.GA11145@willie-the-truck> (raw)
In-Reply-To: <20220318193831.482349-1-oupton@google.com>

On Fri, Mar 18, 2022 at 07:38:29PM +0000, Oliver Upton wrote:
> This series addresses a couple of issues with how KVM exposes SMC64
> calls to its guest. It is currently possible for an AArch32 guest to
> discover the SMC64 SYSTEM_RESET2 function (via
> PSCI_1_0_FN_PSCI_FEATURES) and even make a call to it. SMCCC does not
> allow for 64 bit calls to be made from a 32 bit state.
> 
> Patch 1 cleans up the way we filter SMC64 calls in PSCI. Using a switch
> with case statements for each possibly-filtered function is asking for
> trouble. Instead, pivot off of the bit that indicates the desired
> calling convention. This plugs the PSCI_FEATURES hole for SYSTEM_RESET2.
> 
> Patch 2 adds a check to the PSCI v1.x call handler in KVM, bailing out
> early if the guest is not allowed to use a particular function. This
> closes the door on calls to 64-bit SYSTEM_RESET2 from AArch32.
> 
> My first crack at this [1] was missing the fix for direct calls to
> SYSTEM_RESET2. Taking the patch out of that series and sending
> separately.
> 
> Applies on top of today's kvmarm pull, commit:
> 
>   21ea45784275 ("KVM: arm64: fix typos in comments")
> 
> [1]: https://patchwork.kernel.org/project/kvm/patch/20220311174001.605719-3-oupton@google.com/
> 
> Oliver Upton (2):
>   KVM: arm64: Generally disallow SMC64 for AArch32 guests
>   KVM: arm64: Actually prevent SMC64 SYSTEM_RESET2 from AArch32
> 
>  arch/arm64/kvm/psci.c | 19 ++++++++++---------
>  1 file changed, 10 insertions(+), 9 deletions(-)

For both patches:

Acked-by: Will Deacon <will@kernel.org>

Thanks for fixing this!

Will

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