KVM: arm/arm64: Initialise host's MPIDRs by reading the actual register

As part of setting up the host context, we populate its
MPIDR by using cpu_logical_map(). It turns out that contrary
to arm64, cpu_logical_map() on 32bit ARM doesn't return the
*full* MPIDR, but a truncated version.

This leaves the host MPIDR slightly corrupted after the first
run of a VM, since we won't correctly restore the MPIDR on
exit. Oops.

Since we cannot trust cpu_logical_map(), let's adopt a different
strategy. We move the initialization of the host CPU context as
part of the per-CPU initialization (which, in retrospect, makes
a lot of sense), and directly read the MPIDR from the HW. This
is guaranteed to work on both arm and arm64.

Reported-by: Andre Przywara <Andre.Przywara@arm.com>
Tested-by: Andre Przywara <Andre.Przywara@arm.com>
Fixes: 32f139551954 ("arm/arm64: KVM: Statically configure the host's view of MPIDR")
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

3 files changed, 7 insertions, 9 deletions

diff --git a/arch/arm/include/asm/kvm_host.h b/arch/arm/include/asm/kvm_host.h
index e74e8f408987..8a37c8e89777 100644
--- a/arch/arm/include/asm/kvm_host.h
+++ b/arch/arm/include/asm/kvm_host.h
@@ -15,7 +15,6 @@
 #include <asm/kvm_asm.h>
 #include <asm/kvm_mmio.h>
 #include <asm/fpstate.h>
-#include <asm/smp_plat.h>
 #include <kvm/arm_arch_timer.h>
 
 #define __KVM_HAVE_ARCH_INTC_INITIALIZED
@@ -147,11 +146,10 @@ struct kvm_host_data {
 
 typedef struct kvm_host_data kvm_host_data_t;
 
-static inline void kvm_init_host_cpu_context(struct kvm_cpu_context *cpu_ctxt,
-					     int cpu)
+static inline void kvm_init_host_cpu_context(struct kvm_cpu_context *cpu_ctxt)
 {
 	/* The host's MPIDR is immutable, so let's set it up at boot time */
-	cpu_ctxt->cp15[c0_MPIDR] = cpu_logical_map(cpu);
+	cpu_ctxt->cp15[c0_MPIDR] = read_cpuid_mpidr();
 }
 
 struct vcpu_reset_state {
diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index d9770daf3d7d..63a196c19fed 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -19,12 +19,12 @@
 #include <asm/arch_gicv3.h>
 #include <asm/barrier.h>
 #include <asm/cpufeature.h>
+#include <asm/cputype.h>
 #include <asm/daifflags.h>
 #include <asm/fpsimd.h>
 #include <asm/kvm.h>
 #include <asm/kvm_asm.h>
 #include <asm/kvm_mmio.h>
-#include <asm/smp_plat.h>
 #include <asm/thread_info.h>
 
 #define __KVM_HAVE_ARCH_INTC_INITIALIZED
@@ -484,11 +484,10 @@ struct kvm_vcpu *kvm_mpidr_to_vcpu(struct kvm *kvm, unsigned long mpidr);
 
 DECLARE_PER_CPU(kvm_host_data_t, kvm_host_data);
 
-static inline void kvm_init_host_cpu_context(struct kvm_cpu_context *cpu_ctxt,
-					     int cpu)
+static inline void kvm_init_host_cpu_context(struct kvm_cpu_context *cpu_ctxt)
 {
 	/* The host's MPIDR is immutable, so let's set it up at boot time */
-	cpu_ctxt->sys_regs[MPIDR_EL1] = cpu_logical_map(cpu);
+	cpu_ctxt->sys_regs[MPIDR_EL1] = read_cpuid_mpidr();
 }
 
 void __kvm_enable_ssbs(void);
diff --git a/virt/kvm/arm/arm.c b/virt/kvm/arm/arm.c
index bd5c55916d0d..f149c79fd6ef 100644
--- a/virt/kvm/arm/arm.c
+++ b/virt/kvm/arm/arm.c
@@ -1332,6 +1332,8 @@ static void cpu_hyp_reset(void)
 
 static void cpu_hyp_reinit(void)
 {
+	kvm_init_host_cpu_context(&this_cpu_ptr(&kvm_host_data)->host_ctxt);
+
 	cpu_hyp_reset();
 
 	if (is_kernel_in_hyp_mode())
@@ -1569,7 +1571,6 @@ static int init_hyp_mode(void)
 		kvm_host_data_t *cpu_data;
 
 		cpu_data = per_cpu_ptr(&kvm_host_data, cpu);
-		kvm_init_host_cpu_context(&cpu_data->host_ctxt, cpu);
 		err = create_hyp_mappings(cpu_data, cpu_data + 1, PAGE_HYP);
 
 		if (err) {