linux-kernel - Re: [PATCH v2 06/16] KVM: arm64: Force a full unmap on vpcu reinit

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Date:   Thu, 7 Oct 2021 15:49:22 +0200
From:   Andrew Jones <drjones@...hat.com>
To:     Marc Zyngier <maz@...nel.org>
Cc:     linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.cs.columbia.edu,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org, will@...nel.org,
        qperret@...gle.com, dbrazdil@...gle.com,
        Steven Price <steven.price@....com>,
        Fuad Tabba <tabba@...gle.com>,
        Srivatsa Vaddagiri <vatsa@...eaurora.org>,
        Shanker R Donthineni <sdonthineni@...dia.com>,
        James Morse <james.morse@....com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Alexandru Elisei <alexandru.elisei@....com>,
        kernel-team@...roid.com
Subject: Re: [PATCH v2 06/16] KVM: arm64: Force a full unmap on vpcu reinit

On Mon, Oct 04, 2021 at 06:48:39PM +0100, Marc Zyngier wrote:
> As we now keep information in the S2PT, we must be careful not
> to keep it across a VM reboot, which could otherwise lead to
> interesting problems.
> 
> Make sure that the S2 is completely discarded on reset of
> a vcpu, and remove the flag that enforces the MMIO check.
> 
> Signed-off-by: Marc Zyngier <maz@...nel.org>
> ---
>  arch/arm64/kvm/psci.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/arch/arm64/kvm/psci.c b/arch/arm64/kvm/psci.c
> index 74c47d420253..6c9cb041f764 100644
> --- a/arch/arm64/kvm/psci.c
> +++ b/arch/arm64/kvm/psci.c
> @@ -12,6 +12,7 @@
>  
>  #include <asm/cputype.h>
>  #include <asm/kvm_emulate.h>
> +#include <asm/kvm_mmu.h>
>  
>  #include <kvm/arm_psci.h>
>  #include <kvm/arm_hypercalls.h>
> @@ -180,6 +181,13 @@ static void kvm_prepare_system_event(struct kvm_vcpu *vcpu, u32 type)
>  		tmp->arch.power_off = true;
>  	kvm_make_all_cpus_request(vcpu->kvm, KVM_REQ_SLEEP);
>  
> +	/*
> +	 * If the MMIO guard was enabled, we pay the price of a full
> +	 * unmap to get back to a sane state (and clear the flag).
> +	 */
> +	if (test_and_clear_bit(KVM_ARCH_FLAG_MMIO_GUARD, &vcpu->kvm->arch.flags))
> +		stage2_unmap_vm(vcpu->kvm);
> +
>  	memset(&vcpu->run->system_event, 0, sizeof(vcpu->run->system_event));
>  	vcpu->run->system_event.type = type;
>  	vcpu->run->exit_reason = KVM_EXIT_SYSTEM_EVENT;
> -- 
> 2.30.2
>

Reviewed-by: Andrew Jones <drjones@...hat.com>