[PATCH 1/2] KVM: arm64: Track physical CPU number at EL2

[Fuad Tabba <fuad.tabba@linux.dev>]

The nVHE hypervisor has no equivalent of smp_processor_id(), so EL2 code
has no index for the CPU it runs on.

Add a hyp per-CPU hyp_cpu_number, which the host writes in
cpu_prepare_hyp_mode() before it's deprivileged, and a
hyp_smp_processor_id() accessor to read it. The next patch uses it to
index per-CPU state in a hyp VM.

Signed-off-by: Fuad Tabba <fuad.tabba@linux.dev>
---
 arch/arm64/include/asm/kvm_hyp.h  | 3 +++
 arch/arm64/kvm/arm.c              | 3 +++
 arch/arm64/kvm/hyp/nvhe/hyp-smp.c | 2 ++
 3 files changed, 8 insertions(+)

diff --git a/arch/arm64/include/asm/kvm_hyp.h b/arch/arm64/include/asm/kvm_hyp.h
index b0e42be3d9eef..6c4169a14b73e 100644
--- a/arch/arm64/include/asm/kvm_hyp.h
+++ b/arch/arm64/include/asm/kvm_hyp.h
@@ -16,6 +16,9 @@
 DECLARE_PER_CPU(struct kvm_cpu_context, kvm_hyp_ctxt);
 DECLARE_PER_CPU(unsigned long, kvm_hyp_vector);
 DECLARE_PER_CPU(struct kvm_nvhe_init_params, kvm_init_params);
+DECLARE_PER_CPU(int, hyp_cpu_number);
+
+#define hyp_smp_processor_id() (__this_cpu_read(hyp_cpu_number))
 
 /*
  * Unified accessors for registers that have a different encoding
diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index d593ba9280933..0dd6667f1beea 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -116,6 +116,7 @@ DECLARE_KVM_HYP_PER_CPU(unsigned long, kvm_hyp_vector);
 
 DEFINE_PER_CPU(unsigned long, kvm_arm_hyp_stack_base);
 DECLARE_KVM_NVHE_PER_CPU(struct kvm_nvhe_init_params, kvm_init_params);
+DECLARE_KVM_NVHE_PER_CPU(int, hyp_cpu_number);
 
 DECLARE_KVM_NVHE_PER_CPU(struct kvm_cpu_context, kvm_hyp_ctxt);
 
@@ -2351,6 +2352,8 @@ static void __init cpu_prepare_hyp_mode(int cpu, u32 hyp_va_bits)
 	struct kvm_nvhe_init_params *params = per_cpu_ptr_nvhe_sym(kvm_init_params, cpu);
 	unsigned long tcr;
 
+	*per_cpu_ptr_nvhe_sym(hyp_cpu_number, cpu) = cpu;
+
 	/*
 	 * Calculate the raw per-cpu offset without a translation from the
 	 * kernel's mapping to the linear mapping, and store it in tpidr_el2
diff --git a/arch/arm64/kvm/hyp/nvhe/hyp-smp.c b/arch/arm64/kvm/hyp/nvhe/hyp-smp.c
index 04d194583f1e4..9fcb92abd0b57 100644
--- a/arch/arm64/kvm/hyp/nvhe/hyp-smp.c
+++ b/arch/arm64/kvm/hyp/nvhe/hyp-smp.c
@@ -8,6 +8,8 @@
 #include <asm/kvm_hyp.h>
 #include <asm/kvm_mmu.h>
 
+DEFINE_PER_CPU(int, hyp_cpu_number);
+
 /*
  * nVHE copy of data structures tracking available CPU cores.
  * Only entries for CPUs that were online at KVM init are populated.
-- 
2.39.5