linux-kernel - [RFC PATCH 18/26] kvm: arm64: Intercept PSCI_CPU

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Date:   Wed,  4 Nov 2020 18:36:22 +0000
From:   David Brazdil <dbrazdil@...gle.com>
To:     kvmarm@...ts.cs.columbia.edu
Cc:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Marc Zyngier <maz@...nel.org>,
        James Morse <james.morse@....com>,
        Julien Thierry <julien.thierry.kdev@...il.com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>, 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>,
        Quentin Perret <qperret@...gle.com>,
        Andrew Scull <ascull@...gle.com>, kernel-team@...roid.com,
        David Brazdil <dbrazdil@...gle.com>
Subject: [RFC PATCH 18/26] kvm: arm64: Intercept PSCI_CPU_OFF host SMC calls

Add a handler of the CPU_OFF PSCI host SMC trapped in KVM nVHE hyp code.
When invoked, it changes the recorded state of the core to OFF before
forwarding the call to EL3. If the call fails, it changes the state back
to ON and returns the error to the host.

Signed-off-by: David Brazdil <dbrazdil@...gle.com>
---
 arch/arm64/kvm/hyp/nvhe/psci.c | 30 +++++++++++++++++++++++++++++-
 1 file changed, 29 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/kvm/hyp/nvhe/psci.c b/arch/arm64/kvm/hyp/nvhe/psci.c
index c3d0a6246c66..00dc0cab860c 100644
--- a/arch/arm64/kvm/hyp/nvhe/psci.c
+++ b/arch/arm64/kvm/hyp/nvhe/psci.c
@@ -13,6 +13,8 @@
 #include <kvm/arm_psci.h>
 #include <uapi/linux/psci.h>
 
+#include <nvhe/spinlock.h>
+
 /* Config options set by the host. */
 u32 kvm_host_psci_version = PSCI_VERSION(0, 0);
 u32 kvm_host_psci_function_id[PSCI_FN_MAX];
@@ -20,6 +22,7 @@ s64 hyp_physvirt_offset;
 
 #define __hyp_pa(x) ((phys_addr_t)(x) + hyp_physvirt_offset)
 
+static DEFINE_PER_CPU(hyp_spinlock_t, psci_cpu_lock);
 DEFINE_PER_CPU(enum kvm_nvhe_psci_state, psci_cpu_state);
 
 static u64 get_psci_func_id(struct kvm_cpu_context *host_ctxt)
@@ -76,9 +79,32 @@ static __noreturn unsigned long psci_forward_noreturn(struct kvm_cpu_context *ho
 	hyp_panic(); /* unreachable */
 }
 
+static int psci_cpu_off(u64 func_id, struct kvm_cpu_context *host_ctxt)
+{
+	hyp_spinlock_t *cpu_lock = this_cpu_ptr(&psci_cpu_lock);
+	enum kvm_nvhe_psci_state *cpu_power = this_cpu_ptr(&psci_cpu_state);
+	u32 power_state = (u32)host_ctxt->regs.regs[1];
+	int ret;
+
+	/* Change the recorded state to OFF before forwarding the call. */
+	hyp_spin_lock(cpu_lock);
+	*cpu_power = KVM_NVHE_PSCI_CPU_OFF;
+	hyp_spin_unlock(cpu_lock);
+
+	ret = psci_call(func_id, power_state, 0, 0);
+
+	/* Call was unsuccessful. Restore the recorded state and return to host. */
+	hyp_spin_lock(cpu_lock);
+	*cpu_power = KVM_NVHE_PSCI_CPU_ON;
+	hyp_spin_unlock(cpu_lock);
+	return ret;
+}
+
 static unsigned long psci_0_1_handler(u64 func_id, struct kvm_cpu_context *host_ctxt)
 {
-	if (func_id == kvm_host_psci_function_id[PSCI_FN_MIGRATE])
+	if (func_id == kvm_host_psci_function_id[PSCI_FN_CPU_OFF])
+		return psci_cpu_off(func_id, host_ctxt);
+	else if (func_id == kvm_host_psci_function_id[PSCI_FN_MIGRATE])
 		return psci_forward(host_ctxt);
 	else
 		return PSCI_RET_NOT_SUPPORTED;
@@ -97,6 +123,8 @@ static unsigned long psci_0_2_handler(u64 func_id, struct kvm_cpu_context *host_
 	case PSCI_0_2_FN_SYSTEM_RESET:
 		psci_forward_noreturn(host_ctxt);
 		unreachable();
+	case PSCI_0_2_FN_CPU_OFF:
+		return psci_cpu_off(func_id, host_ctxt);
 	default:
 		return PSCI_RET_NOT_SUPPORTED;
 	}
-- 
2.29.1.341.ge80a0c044ae-goog