From 6a97c775ff77fb7c54adc3f7944205ae66cb5475 Mon Sep 17 00:00:00 2001 From: James Hogan Date: Thu, 23 Apr 2015 16:54:35 +0100 Subject: KVM: MIPS: Use CP0_BadInstr[P] for emulation MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit When exiting from the guest, store the values of the CP0_BadInstr and CP0_BadInstrP registers if they exist, which contain the encodings of the instructions which caused the last synchronous exception. When the instruction is needed for emulation, kvm_get_badinstr() and kvm_get_badinstrp() are used instead of calling kvm_get_inst() directly, to decide whether to read the saved CP0_BadInstr/CP0_BadInstrP registers (if they exist), or read the instruction from memory (if not). The use of these registers should be more robust than using kvm_get_inst(), as it actually gives the instruction encoding seen by the hardware rather than relying on user accessors after the fact, which can be fooled by incoherent icache or a racing code modification. It will also work with VZ, where the guest virtual memory isn't directly accessible by the host with user accessors. 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/kvm/emulate.c | 48 +++++++++++++++++++++++++++++++++++++++++++++--- arch/mips/kvm/entry.c | 14 ++++++++++++++ arch/mips/kvm/mips.c | 2 +- 3 files changed, 60 insertions(+), 4 deletions(-) (limited to 'arch/mips/kvm') diff --git a/arch/mips/kvm/emulate.c b/arch/mips/kvm/emulate.c index b906fc0589f3..b295a4a1496f 100644 --- a/arch/mips/kvm/emulate.c +++ b/arch/mips/kvm/emulate.c @@ -54,7 +54,7 @@ static int kvm_compute_return_epc(struct kvm_vcpu *vcpu, unsigned long instpc, } /* Read the instruction */ - err = kvm_get_inst((u32 *)epc, vcpu, &insn.word); + err = kvm_get_badinstrp((u32 *)epc, vcpu, &insn.word); if (err) return err; @@ -258,6 +258,48 @@ enum emulation_result update_pc(struct kvm_vcpu *vcpu, u32 cause) return EMULATE_DONE; } +/** + * kvm_get_badinstr() - Get bad instruction encoding. + * @opc: Guest pointer to faulting instruction. + * @vcpu: KVM VCPU information. + * + * Gets the instruction encoding of the faulting instruction, using the saved + * BadInstr register value if it exists, otherwise falling back to reading guest + * memory at @opc. + * + * Returns: The instruction encoding of the faulting instruction. + */ +int kvm_get_badinstr(u32 *opc, struct kvm_vcpu *vcpu, u32 *out) +{ + if (cpu_has_badinstr) { + *out = vcpu->arch.host_cp0_badinstr; + return 0; + } else { + return kvm_get_inst(opc, vcpu, out); + } +} + +/** + * kvm_get_badinstrp() - Get bad prior instruction encoding. + * @opc: Guest pointer to prior faulting instruction. + * @vcpu: KVM VCPU information. + * + * Gets the instruction encoding of the prior faulting instruction (the branch + * containing the delay slot which faulted), using the saved BadInstrP register + * value if it exists, otherwise falling back to reading guest memory at @opc. + * + * Returns: The instruction encoding of the prior faulting instruction. + */ +int kvm_get_badinstrp(u32 *opc, struct kvm_vcpu *vcpu, u32 *out) +{ + if (cpu_has_badinstrp) { + *out = vcpu->arch.host_cp0_badinstrp; + return 0; + } else { + return kvm_get_inst(opc, vcpu, out); + } +} + /** * kvm_mips_count_disabled() - Find whether the CP0_Count timer is disabled. * @vcpu: Virtual CPU. @@ -1839,7 +1881,7 @@ enum emulation_result kvm_mips_emulate_inst(u32 cause, u32 *opc, /* Fetch the instruction. */ if (cause & CAUSEF_BD) opc += 1; - err = kvm_get_inst(opc, vcpu, &inst.word); + err = kvm_get_badinstr(opc, vcpu, &inst.word); if (err) return EMULATE_FAIL; @@ -2434,7 +2476,7 @@ enum emulation_result kvm_mips_handle_ri(u32 cause, u32 *opc, /* Fetch the instruction. */ if (cause & CAUSEF_BD) opc += 1; - err = kvm_get_inst(opc, vcpu, &inst.word); + err = kvm_get_badinstr(opc, vcpu, &inst.word); if (err) { kvm_err("%s: Cannot get inst @ %p (%d)\n", __func__, opc, err); return EMULATE_FAIL; diff --git a/arch/mips/kvm/entry.c b/arch/mips/kvm/entry.c index 1ae33e0e675c..c5b254c4d0da 100644 --- a/arch/mips/kvm/entry.c +++ b/arch/mips/kvm/entry.c @@ -53,6 +53,8 @@ /* Some CP0 registers */ #define C0_HWRENA 7, 0 #define C0_BADVADDR 8, 0 +#define C0_BADINSTR 8, 1 +#define C0_BADINSTRP 8, 2 #define C0_ENTRYHI 10, 0 #define C0_STATUS 12, 0 #define C0_CAUSE 13, 0 @@ -579,6 +581,18 @@ void *kvm_mips_build_exit(void *addr) uasm_i_mfc0(&p, K0, C0_CAUSE); uasm_i_sw(&p, K0, offsetof(struct kvm_vcpu_arch, host_cp0_cause), K1); + if (cpu_has_badinstr) { + uasm_i_mfc0(&p, K0, C0_BADINSTR); + uasm_i_sw(&p, K0, offsetof(struct kvm_vcpu_arch, + host_cp0_badinstr), K1); + } + + if (cpu_has_badinstrp) { + uasm_i_mfc0(&p, K0, C0_BADINSTRP); + uasm_i_sw(&p, K0, offsetof(struct kvm_vcpu_arch, + host_cp0_badinstrp), K1); + } + /* Now restore the host state just enough to run the handlers */ /* Switch EBASE to the one used by Linux */ diff --git a/arch/mips/kvm/mips.c b/arch/mips/kvm/mips.c index 29afd96069ef..b8f04070bf39 100644 --- a/arch/mips/kvm/mips.c +++ b/arch/mips/kvm/mips.c @@ -1471,7 +1471,7 @@ int kvm_mips_handle_exit(struct kvm_run *run, struct kvm_vcpu *vcpu) if (cause & CAUSEF_BD) opc += 1; inst = 0; - kvm_get_inst(opc, vcpu, &inst); + kvm_get_badinstr(opc, vcpu, &inst); kvm_err("Exception Code: %d, not yet handled, @ PC: %p, inst: 0x%08x BadVaddr: %#lx Status: %#lx\n", exccode, opc, inst, badvaddr, kvm_read_c0_guest_status(vcpu->arch.cop0)); -- cgit v1.2.3