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

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Message-ID: <20201201132032.we4jbsvtsngwixse@google.com>
Date:   Tue, 1 Dec 2020 13:20:32 +0000
From:   David Brazdil <dbrazdil@...gle.com>
To:     Sudeep Holla <sudeep.holla@....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 Fri, Nov 27, 2020 at 04:51:59PM +0000, Sudeep Holla wrote:
> 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 ?

Sure, happy to combine them. I thought visually it made sense to have one
action per ID.