KVM: MIPS/T&E: Handle read only GPA in TLB mod

Rewrite TLB modified exception handling to handle read only GPA memory
regions, instead of unconditionally passing the exception to the guest.

If the guest TLB is not the cause of the exception we call into the
normal TLB fault handling depending on the memory segment, which will
soon attempt to remap the physical page to be writable (handling dirty
page tracking or copy on write in the process).

Failing that we fall back to treating it as MMIO, due to a read only
memory region. Once the capability is enabled, this will allow read only
memory regions (such as the Malta boot flash as emulated by QEMU) to
have writes treated as MMIO, while still allowing reads to run
untrapped.

Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Radim Krčmář" <rkrcmar@redhat.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Cc: kvm@vger.kernel.org

1 files changed, 0 insertions, 31 deletions

diff --git a/arch/mips/kvm/emulate.c b/arch/mips/kvm/emulate.c
index 4875afca3f26..b6cafb0a9df4 100644
--- a/arch/mips/kvm/emulate.c
+++ b/arch/mips/kvm/emulate.c
@@ -2124,37 +2124,6 @@ enum emulation_result kvm_mips_emulate_tlbinv_st(u32 cause,
 	return EMULATE_DONE;
 }
 
-/* TLBMOD: store into address matching TLB with Dirty bit off */
-enum emulation_result kvm_mips_handle_tlbmod(u32 cause, u32 *opc,
-					     struct kvm_run *run,
-					     struct kvm_vcpu *vcpu)
-{
-	enum emulation_result er = EMULATE_DONE;
-#ifdef DEBUG
-	struct mips_coproc *cop0 = vcpu->arch.cop0;
-	unsigned long entryhi = (vcpu->arch.host_cp0_badvaddr & VPN2_MASK) |
-			(kvm_read_c0_guest_entryhi(cop0) & KVM_ENTRYHI_ASID);
-	bool kernel = KVM_GUEST_KERNEL_MODE(vcpu);
-	int index;
-
-	/* If address not in the guest TLB, then we are in trouble */
-	index = kvm_mips_guest_tlb_lookup(vcpu, entryhi);
-	if (index < 0) {
-		/* XXXKYMA Invalidate and retry */
-		kvm_mips_host_tlb_inv(vcpu, vcpu->arch.host_cp0_badvaddr,
-				      !kernel, kernel);
-		kvm_err("%s: host got TLBMOD for %#lx but entry not present in Guest TLB\n",
-		     __func__, entryhi);
-		kvm_mips_dump_guest_tlbs(vcpu);
-		kvm_mips_dump_host_tlbs();
-		return EMULATE_FAIL;
-	}
-#endif
-
-	er = kvm_mips_emulate_tlbmod(cause, opc, run, vcpu);
-	return er;
-}
-
 enum emulation_result kvm_mips_emulate_tlbmod(u32 cause,
 					      u32 *opc,
 					      struct kvm_run *run,