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    Subject[PATCH v3 09/13] arm64: KVM: Make PSCI_VERSION a fast path
    Date
    From: Marc Zyngier <marc.zyngier@arm.com>

    For those CPUs that require PSCI to perform a BP invalidation,
    going all the way to the PSCI code for not much is a waste of
    precious cycles. Let's terminate that call as early as possible.

    Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
    Signed-off-by: Will Deacon <will.deacon@arm.com>
    ---
    arch/arm64/kvm/hyp/switch.c | 13 +++++++++++++
    1 file changed, 13 insertions(+)

    diff --git a/arch/arm64/kvm/hyp/switch.c b/arch/arm64/kvm/hyp/switch.c
    index 8d4f3c9d6dc4..4d273f6d0e69 100644
    --- a/arch/arm64/kvm/hyp/switch.c
    +++ b/arch/arm64/kvm/hyp/switch.c
    @@ -17,6 +17,7 @@

    #include <linux/types.h>
    #include <linux/jump_label.h>
    +#include <uapi/linux/psci.h>

    #include <asm/kvm_asm.h>
    #include <asm/kvm_emulate.h>
    @@ -341,6 +342,18 @@ int __hyp_text __kvm_vcpu_run(struct kvm_vcpu *vcpu)
    if (exit_code == ARM_EXCEPTION_TRAP && !__populate_fault_info(vcpu))
    goto again;

    + if (exit_code == ARM_EXCEPTION_TRAP &&
    + (kvm_vcpu_trap_get_class(vcpu) == ESR_ELx_EC_HVC64 ||
    + kvm_vcpu_trap_get_class(vcpu) == ESR_ELx_EC_HVC32) &&
    + vcpu_get_reg(vcpu, 0) == PSCI_0_2_FN_PSCI_VERSION) {
    + u64 val = PSCI_RET_NOT_SUPPORTED;
    + if (test_bit(KVM_ARM_VCPU_PSCI_0_2, vcpu->arch.features))
    + val = 2;
    +
    + vcpu_set_reg(vcpu, 0, val);
    + goto again;
    + }
    +
    if (static_branch_unlikely(&vgic_v2_cpuif_trap) &&
    exit_code == ARM_EXCEPTION_TRAP) {
    bool valid;
    --
    2.1.4
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