Commit 6a97c775 authored by James Hogan's avatar James Hogan

KVM: MIPS: Use CP0_BadInstr[P] for emulation

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: default avatarJames 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
parent 122e51d4
...@@ -280,6 +280,8 @@ struct kvm_vcpu_arch { ...@@ -280,6 +280,8 @@ struct kvm_vcpu_arch {
unsigned long host_cp0_badvaddr; unsigned long host_cp0_badvaddr;
unsigned long host_cp0_epc; unsigned long host_cp0_epc;
u32 host_cp0_cause; u32 host_cp0_cause;
u32 host_cp0_badinstr;
u32 host_cp0_badinstrp;
/* GPRS */ /* GPRS */
unsigned long gprs[32]; unsigned long gprs[32];
...@@ -641,6 +643,8 @@ void kvm_trap_emul_invalidate_gva(struct kvm_vcpu *vcpu, unsigned long addr, ...@@ -641,6 +643,8 @@ void kvm_trap_emul_invalidate_gva(struct kvm_vcpu *vcpu, unsigned long addr,
/* Emulation */ /* Emulation */
int kvm_get_inst(u32 *opc, struct kvm_vcpu *vcpu, u32 *out); int kvm_get_inst(u32 *opc, struct kvm_vcpu *vcpu, u32 *out);
enum emulation_result update_pc(struct kvm_vcpu *vcpu, u32 cause); enum emulation_result update_pc(struct kvm_vcpu *vcpu, u32 cause);
int kvm_get_badinstr(u32 *opc, struct kvm_vcpu *vcpu, u32 *out);
int kvm_get_badinstrp(u32 *opc, struct kvm_vcpu *vcpu, u32 *out);
/** /**
* kvm_is_ifetch_fault() - Find whether a TLBL exception is due to ifetch fault. * kvm_is_ifetch_fault() - Find whether a TLBL exception is due to ifetch fault.
......
...@@ -54,7 +54,7 @@ static int kvm_compute_return_epc(struct kvm_vcpu *vcpu, unsigned long instpc, ...@@ -54,7 +54,7 @@ static int kvm_compute_return_epc(struct kvm_vcpu *vcpu, unsigned long instpc,
} }
/* Read the instruction */ /* Read the instruction */
err = kvm_get_inst((u32 *)epc, vcpu, &insn.word); err = kvm_get_badinstrp((u32 *)epc, vcpu, &insn.word);
if (err) if (err)
return err; return err;
...@@ -258,6 +258,48 @@ enum emulation_result update_pc(struct kvm_vcpu *vcpu, u32 cause) ...@@ -258,6 +258,48 @@ enum emulation_result update_pc(struct kvm_vcpu *vcpu, u32 cause)
return EMULATE_DONE; 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. * kvm_mips_count_disabled() - Find whether the CP0_Count timer is disabled.
* @vcpu: Virtual CPU. * @vcpu: Virtual CPU.
...@@ -1839,7 +1881,7 @@ enum emulation_result kvm_mips_emulate_inst(u32 cause, u32 *opc, ...@@ -1839,7 +1881,7 @@ enum emulation_result kvm_mips_emulate_inst(u32 cause, u32 *opc,
/* Fetch the instruction. */ /* Fetch the instruction. */
if (cause & CAUSEF_BD) if (cause & CAUSEF_BD)
opc += 1; opc += 1;
err = kvm_get_inst(opc, vcpu, &inst.word); err = kvm_get_badinstr(opc, vcpu, &inst.word);
if (err) if (err)
return EMULATE_FAIL; return EMULATE_FAIL;
...@@ -2434,7 +2476,7 @@ enum emulation_result kvm_mips_handle_ri(u32 cause, u32 *opc, ...@@ -2434,7 +2476,7 @@ enum emulation_result kvm_mips_handle_ri(u32 cause, u32 *opc,
/* Fetch the instruction. */ /* Fetch the instruction. */
if (cause & CAUSEF_BD) if (cause & CAUSEF_BD)
opc += 1; opc += 1;
err = kvm_get_inst(opc, vcpu, &inst.word); err = kvm_get_badinstr(opc, vcpu, &inst.word);
if (err) { if (err) {
kvm_err("%s: Cannot get inst @ %p (%d)\n", __func__, opc, err); kvm_err("%s: Cannot get inst @ %p (%d)\n", __func__, opc, err);
return EMULATE_FAIL; return EMULATE_FAIL;
......
...@@ -53,6 +53,8 @@ ...@@ -53,6 +53,8 @@
/* Some CP0 registers */ /* Some CP0 registers */
#define C0_HWRENA 7, 0 #define C0_HWRENA 7, 0
#define C0_BADVADDR 8, 0 #define C0_BADVADDR 8, 0
#define C0_BADINSTR 8, 1
#define C0_BADINSTRP 8, 2
#define C0_ENTRYHI 10, 0 #define C0_ENTRYHI 10, 0
#define C0_STATUS 12, 0 #define C0_STATUS 12, 0
#define C0_CAUSE 13, 0 #define C0_CAUSE 13, 0
...@@ -579,6 +581,18 @@ void *kvm_mips_build_exit(void *addr) ...@@ -579,6 +581,18 @@ void *kvm_mips_build_exit(void *addr)
uasm_i_mfc0(&p, K0, C0_CAUSE); uasm_i_mfc0(&p, K0, C0_CAUSE);
uasm_i_sw(&p, K0, offsetof(struct kvm_vcpu_arch, host_cp0_cause), K1); 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 */ /* Now restore the host state just enough to run the handlers */
/* Switch EBASE to the one used by Linux */ /* Switch EBASE to the one used by Linux */
......
...@@ -1471,7 +1471,7 @@ int kvm_mips_handle_exit(struct kvm_run *run, struct kvm_vcpu *vcpu) ...@@ -1471,7 +1471,7 @@ int kvm_mips_handle_exit(struct kvm_run *run, struct kvm_vcpu *vcpu)
if (cause & CAUSEF_BD) if (cause & CAUSEF_BD)
opc += 1; opc += 1;
inst = 0; 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", kvm_err("Exception Code: %d, not yet handled, @ PC: %p, inst: 0x%08x BadVaddr: %#lx Status: %#lx\n",
exccode, opc, inst, badvaddr, exccode, opc, inst, badvaddr,
kvm_read_c0_guest_status(vcpu->arch.cop0)); kvm_read_c0_guest_status(vcpu->arch.cop0));
......
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