[PATCH 12/30] KVM: MIPS/T&E: active_mm = init_mm in guest context

[James Hogan <james.hogan@xxxxxxxxxx>]

Set init_mm as the active_mm and update mm_cpumask(current->mm) to
reflect that it isn't active when in guest context. This prevents cache
management code from attempting cache flushes on host virtual addresses
while in guest context, for example due to a cache management IPIs or
later when writing of dynamically translated code hits copy on write.

Signed-off-by: James Hogan <james.hogan@xxxxxxxxxx>
Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Cc: "Radim Krčmář" <rkrcmar@xxxxxxxxxx>
Cc: Ralf Baechle <ralf@xxxxxxxxxxxxxx>
Cc: linux-mips@xxxxxxxxxxxxxx
Cc: kvm@xxxxxxxxxxxxxxx
---
 arch/mips/kvm/trap_emul.c | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/arch/mips/kvm/trap_emul.c b/arch/mips/kvm/trap_emul.c
index 3e1dbcbcea85..ab3750f6a768 100644
--- a/arch/mips/kvm/trap_emul.c
+++ b/arch/mips/kvm/trap_emul.c
@@ -670,6 +670,8 @@ static int kvm_trap_emul_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
 			write_c0_entryhi(cpu_asid(cpu, kern_mm));
 		else
 			write_c0_entryhi(cpu_asid(cpu, user_mm));
+		cpumask_clear_cpu(cpu, mm_cpumask(current->active_mm));
+		current->active_mm = &init_mm;
 		ehb();
 	}
 
@@ -689,6 +691,8 @@ static int kvm_trap_emul_vcpu_put(struct kvm_vcpu *vcpu, int cpu)
 			get_new_mmu_context(current->mm, cpu);
 		}
 		write_c0_entryhi(cpu_asid(cpu, current->mm));
+		cpumask_set_cpu(cpu, mm_cpumask(current->mm));
+		current->active_mm = current->mm;
 		ehb();
 	}
 
@@ -723,7 +727,7 @@ static void kvm_trap_emul_vcpu_reenter(struct kvm_run *run,
 
 static int kvm_trap_emul_vcpu_run(struct kvm_run *run, struct kvm_vcpu *vcpu)
 {
-	int cpu;
+	int cpu = smp_processor_id();
 	int r;
 
 	/* Check if we have any exceptions/interrupts pending */
@@ -735,6 +739,14 @@ static int kvm_trap_emul_vcpu_run(struct kvm_run *run, struct kvm_vcpu *vcpu)
 	/* Disable hardware page table walking while in guest */
 	htw_stop();
 
+	/*
+	 * While in guest context we're in the guest's address space, not the
+	 * host process address space, so we need to be careful not to confuse
+	 * e.g. cache management IPIs.
+	 */
+	cpumask_clear_cpu(cpu, mm_cpumask(current->active_mm));
+	current->active_mm = &init_mm;
+
 	r = vcpu->arch.vcpu_run(run, vcpu);
 
 	/* We may have migrated while handling guest exits */
@@ -745,6 +757,8 @@ static int kvm_trap_emul_vcpu_run(struct kvm_run *run, struct kvm_vcpu *vcpu)
 	     asid_version_mask(cpu)))
 		get_new_mmu_context(current->mm, cpu);
 	write_c0_entryhi(cpu_asid(cpu, current->mm));
+	cpumask_set_cpu(cpu, mm_cpumask(current->mm));
+	current->active_mm = current->mm;
 
 	htw_start();
 
-- 
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