KVM: arm64: Introduce __pkvm_tlb_flush_vmid()

Introduce a new hypercall to flush the TLBs of non-protected guests. The
host kernel will be responsible for issuing this hypercall after changing
stage-2 permissions using the __pkvm_host_relax_guest_perms() or
__pkvm_host_wrprotect_guest() paths. This is left under the host's
responsibility for performance reasons.

Note however that the TLB maintenance for all *unmap* operations still
remains entirely under the hypervisor's responsibility for security
reasons -- an unmapped page may be donated to another entity, so a stale
TLB entry could be used to leak private data.

Tested-by: Fuad Tabba <tabba@google.com>
Reviewed-by: Fuad Tabba <tabba@google.com>
Signed-off-by: Quentin Perret <qperret@google.com>
Link: https://lore.kernel.org/r/20241218194059.3670226-17-qperret@google.com
Signed-off-by: Marc Zyngier <maz@kernel.org>

diff --git a/arch/arm64/include/asm/kvm_asm.h b/arch/arm64/include/asm/kvm_asm.h
index a3b07db2776c6271e8ea9ac674035e6670eea40e..002088c6e2978d910c5e04f1deeab7c9d1e1d95f 100644 (file)
--- a/arch/arm64/include/asm/kvm_asm.h
+++ b/arch/arm64/include/asm/kvm_asm.h
@@ -87,6 +87,7 @@ enum __kvm_host_smccc_func {
        __KVM_HOST_SMCCC_FUNC___pkvm_teardown_vm,
        __KVM_HOST_SMCCC_FUNC___pkvm_vcpu_load,
        __KVM_HOST_SMCCC_FUNC___pkvm_vcpu_put,
+       __KVM_HOST_SMCCC_FUNC___pkvm_tlb_flush_vmid,
 };
 
 #define DECLARE_KVM_VHE_SYM(sym)       extern char sym[]

diff --git a/arch/arm64/kvm/hyp/nvhe/hyp-main.c b/arch/arm64/kvm/hyp/nvhe/hyp-main.c
index 32c4627b5b5b26dd3177b30bf3ba67105d26770f..130f5f23bcb589ca94766dc5c13d44bc03df7d07 100644 (file)
--- a/arch/arm64/kvm/hyp/nvhe/hyp-main.c
+++ b/arch/arm64/kvm/hyp/nvhe/hyp-main.c
@@ -389,6 +389,22 @@ static void handle___kvm_tlb_flush_vmid(struct kvm_cpu_context *host_ctxt)
        __kvm_tlb_flush_vmid(kern_hyp_va(mmu));
 }
 
+static void handle___pkvm_tlb_flush_vmid(struct kvm_cpu_context *host_ctxt)
+{
+       DECLARE_REG(pkvm_handle_t, handle, host_ctxt, 1);
+       struct pkvm_hyp_vm *hyp_vm;
+
+       if (!is_protected_kvm_enabled())
+               return;
+
+       hyp_vm = get_np_pkvm_hyp_vm(handle);
+       if (!hyp_vm)
+               return;
+
+       __kvm_tlb_flush_vmid(&hyp_vm->kvm.arch.mmu);
+       put_pkvm_hyp_vm(hyp_vm);
+}
+
 static void handle___kvm_flush_cpu_context(struct kvm_cpu_context *host_ctxt)
 {
        DECLARE_REG(struct kvm_s2_mmu *, mmu, host_ctxt, 1);
@@ -573,6 +589,7 @@ static const hcall_t host_hcall[] = {
        HANDLE_FUNC(__pkvm_teardown_vm),
        HANDLE_FUNC(__pkvm_vcpu_load),
        HANDLE_FUNC(__pkvm_vcpu_put),
+       HANDLE_FUNC(__pkvm_tlb_flush_vmid),
 };
 
 static void handle_host_hcall(struct kvm_cpu_context *host_ctxt)