From a1ecc54d7ea629538116351a3ccc7d86bb9a3c69 Mon Sep 17 00:00:00 2001 From: James Hogan Date: Mon, 28 Nov 2016 18:39:24 +0000 Subject: [PATCH] KVM: MIPS/T&E: Don't treat code fetch faults as MMIO MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit In order to make use of the CP0_BadInstr & CP0_BadInstrP registers we need to be a bit more careful not to treat code fetch faults as MMIO, lest we hit an UNPREDICTABLE register value when we try to emulate the MMIO load instruction but there was no valid instruction word available to the hardware. Add a kvm_is_ifetch_fault() helper to try to figure out whether a load fault was due to a code fetch, and prevent MMIO instruction emulation in that case. Signed-off-by: James Hogan Cc: Paolo Bonzini Cc: "Radim Krčmář" Cc: Ralf Baechle Cc: linux-mips@linux-mips.org Cc: kvm@vger.kernel.org --- arch/mips/include/asm/kvm_host.h | 27 +++++++++++++++++++++++++++ arch/mips/kvm/trap_emul.c | 12 ++++++++++++ 2 files changed, 39 insertions(+) diff --git a/arch/mips/include/asm/kvm_host.h b/arch/mips/include/asm/kvm_host.h index 1337abb..6f68f75 100644 --- a/arch/mips/include/asm/kvm_host.h +++ b/arch/mips/include/asm/kvm_host.h @@ -643,6 +643,33 @@ void kvm_trap_emul_invalidate_gva(struct kvm_vcpu *vcpu, unsigned long addr, u32 kvm_get_inst(u32 *opc, struct kvm_vcpu *vcpu); enum emulation_result update_pc(struct kvm_vcpu *vcpu, u32 cause); +/** + * kvm_is_ifetch_fault() - Find whether a TLBL exception is due to ifetch fault. + * @vcpu: Virtual CPU. + * + * Returns: Whether the TLBL exception was likely due to an instruction + * fetch fault rather than a data load fault. + */ +static inline bool kvm_is_ifetch_fault(struct kvm_vcpu_arch *vcpu) +{ + unsigned long badvaddr = vcpu->host_cp0_badvaddr; + unsigned long epc = msk_isa16_mode(vcpu->pc); + u32 cause = vcpu->host_cp0_cause; + + if (epc == badvaddr) + return true; + + /* + * Branches may be 32-bit or 16-bit instructions. + * This isn't exact, but we don't really support MIPS16 or microMIPS yet + * in KVM anyway. + */ + if ((cause & CAUSEF_BD) && badvaddr - epc <= 4) + return true; + + return false; +} + extern enum emulation_result kvm_mips_emulate_inst(u32 cause, u32 *opc, struct kvm_run *run, diff --git a/arch/mips/kvm/trap_emul.c b/arch/mips/kvm/trap_emul.c index 653850c..ccd56b3 100644 --- a/arch/mips/kvm/trap_emul.c +++ b/arch/mips/kvm/trap_emul.c @@ -178,6 +178,12 @@ static int kvm_trap_emul_handle_tlb_miss(struct kvm_vcpu *vcpu, bool store) } } else if (KVM_GUEST_KERNEL_MODE(vcpu) && (KSEGX(badvaddr) == CKSEG0 || KSEGX(badvaddr) == CKSEG1)) { + /* A code fetch fault doesn't count as an MMIO */ + if (!store && kvm_is_ifetch_fault(&vcpu->arch)) { + run->exit_reason = KVM_EXIT_INTERNAL_ERROR; + return RESUME_HOST; + } + /* * With EVA we may get a TLB exception instead of an address * error when the guest performs MMIO to KSeg1 addresses. @@ -255,6 +261,12 @@ static int kvm_trap_emul_handle_addr_err_ld(struct kvm_vcpu *vcpu) int ret = RESUME_GUEST; if (KSEGX(badvaddr) == CKSEG0 || KSEGX(badvaddr) == CKSEG1) { + /* A code fetch fault doesn't count as an MMIO */ + if (kvm_is_ifetch_fault(&vcpu->arch)) { + run->exit_reason = KVM_EXIT_INTERNAL_ERROR; + return RESUME_HOST; + } + kvm_debug("Emulate Load from MMIO space @ %#lx\n", badvaddr); er = kvm_mips_emulate_inst(cause, opc, run, vcpu); if (er == EMULATE_FAIL) { -- 2.7.4