linux-kernel - Re: [PATCH v3 16/23] kvm: arm64: Forward safe PSCI SMCs coming from host

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Message-ID: <20201127165159.3s7hob5tgjcrbz33@bogus>
Date:   Fri, 27 Nov 2020 16:51:59 +0000
From:   Sudeep Holla <sudeep.holla@....com>
To:     David Brazdil <dbrazdil@...gle.com>
Cc:     kvmarm@...ts.cs.columbia.edu, Jonathan Corbet <corbet@....net>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>, Marc Zyngier <maz@...nel.org>,
        James Morse <james.morse@....com>,
        Julien Thierry <julien.thierry.kdev@...il.com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Dennis Zhou <dennis@...nel.org>, Tejun Heo <tj@...nel.org>,
        Christoph Lameter <cl@...ux.com>,
        Mark Rutland <mark.rutland@....com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, kernel-team@...roid.com
Subject: Re: [PATCH v3 16/23] kvm: arm64: Forward safe PSCI SMCs coming from
 host

On Thu, Nov 26, 2020 at 03:54:14PM +0000, David Brazdil wrote:
> Forward the following PSCI SMCs issued by host to EL3 as they do not
> require the hypervisor's intervention. This assumes that EL3 correctly
> implements the PSCI specification.
> 
> Only function IDs implemented in Linux are included.
> 
> Where both 32-bit and 64-bit variants exist, it is assumed that the host
> will always use the 64-bit variant.
> 
>  * SMCs that only return information about the system
>    * PSCI_VERSION        - PSCI version implemented by EL3
>    * PSCI_FEATURES       - optional features supported by EL3
>    * AFFINITY_INFO       - power state of core/cluster
>    * MIGRATE_INFO_TYPE   - whether Trusted OS can be migrated
>    * MIGRATE_INFO_UP_CPU - resident core of Trusted OS
>  * operations which do not affect the hypervisor
>    * MIGRATE             - migrate Trusted OS to a different core
>    * SET_SUSPEND_MODE    - toggle OS-initiated mode
>  * system shutdown/reset
>    * SYSTEM_OFF
>    * SYSTEM_RESET
>    * SYSTEM_RESET2
> 
> Signed-off-by: David Brazdil <dbrazdil@...gle.com>
> ---
>  arch/arm64/kvm/hyp/nvhe/psci-relay.c | 43 +++++++++++++++++++++++++++-
>  1 file changed, 42 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/arm64/kvm/hyp/nvhe/psci-relay.c b/arch/arm64/kvm/hyp/nvhe/psci-relay.c
> index e7091d89f0fc..7aa87ab7f5ce 100644
> --- a/arch/arm64/kvm/hyp/nvhe/psci-relay.c
> +++ b/arch/arm64/kvm/hyp/nvhe/psci-relay.c
> @@ -57,14 +57,51 @@ static bool is_psci_call(u64 func_id)
>  	}
>  }
>  
> +static unsigned long psci_call(unsigned long fn, unsigned long arg0,
> +			       unsigned long arg1, unsigned long arg2)
> +{
> +	struct arm_smccc_res res;
> +
> +	arm_smccc_1_1_smc(fn, arg0, arg1, arg2, &res);
> +	return res.a0;
> +}
> +
> +static unsigned long psci_forward(struct kvm_cpu_context *host_ctxt)
> +{
> +	return psci_call(cpu_reg(host_ctxt, 0), cpu_reg(host_ctxt, 1),
> +			 cpu_reg(host_ctxt, 2), cpu_reg(host_ctxt, 3));
> +}
> +
> +static __noreturn unsigned long psci_forward_noreturn(struct kvm_cpu_context *host_ctxt)
> +{
> +	psci_forward(host_ctxt);
> +	hyp_panic(); /* unreachable */
> +}
> +
>  static unsigned long psci_0_1_handler(u64 func_id, struct kvm_cpu_context *host_ctxt)
>  {
> -	return PSCI_RET_NOT_SUPPORTED;
> +	if (func_id == kvm_host_psci_function_id[PSCI_FN_CPU_OFF])
> +		return psci_forward(host_ctxt);
> +	else if (func_id == kvm_host_psci_function_id[PSCI_FN_MIGRATE])
> +		return psci_forward(host_ctxt);

Looks weird or I am not seeing something right ? Same action for both
right ? Can't they be combined ?

-- 
Regards,
Sudeep