From: Rusty Russell <rusty at rustcorp.com.au>
Conditional instructions may trap even if the condition isn't true, so a good
hypervisor will check this. The same can happen with undefined instructions,
so the kernel should be doing this dance already (it isn't).
(See p1206 of ARMv7-A ARM)
This is difficult to test, since the fastmodel doesn't give such spurious
traps, but it does verify that conditional traps are intended.
Signed-off-by: Rusty Russell <rusty at rustcorp.com.au>
---
arch/arm/include/asm/kvm_arm.h | 4 +++
arch/arm/include/asm/kvm_emulate.h | 2 +
arch/arm/kvm/Makefile | 2 +
arch/arm/kvm/arm.c | 3 ++
arch/arm/kvm/emulate.c | 41 +++++++++++++++++++++++++++
arch/arm/kvm/kvm_cond_match.S | 54 ++++++++++++++++++++++++++++++++++++
6 files changed, 105 insertions(+), 1 deletions(-)
create mode 100644 arch/arm/kvm/kvm_cond_match.S
diff --git a/arch/arm/include/asm/kvm_arm.h b/arch/arm/include/asm/kvm_arm.h
index 1769187..156284a 100644
--- a/arch/arm/include/asm/kvm_arm.h
+++ b/arch/arm/include/asm/kvm_arm.h
@@ -107,6 +107,10 @@
#define HSR_ISS (HSR_IL - 1)
#define HSR_ISV_SHIFT (24)
#define HSR_ISV (1U << HSR_ISV_SHIFT)
+#define HSR_CV_SHIFT (24)
+#define HSR_CV (1U << HSR_CV_SHIFT)
+#define HSR_COND_SHIFT (20)
+#define HSR_COND (0xfU << HSR_COND_SHIFT)
#define HSR_EC_UNKNOWN (0x00)
#define HSR_EC_WFI (0x01)
diff --git a/arch/arm/include/asm/kvm_emulate.h b/arch/arm/include/asm/kvm_emulate.h
index fa54247..fe21e86 100644
--- a/arch/arm/include/asm/kvm_emulate.h
+++ b/arch/arm/include/asm/kvm_emulate.h
@@ -49,6 +49,8 @@ int kvm_handle_cp15_64(struct kvm_vcpu *vcpu, struct kvm_run *run);
int kvm_handle_wfi(struct kvm_vcpu *vcpu, struct kvm_run *run);
int kvm_emulate_mmio_ls(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
unsigned long instr);
+bool kvm_should_not_have_trapped(struct kvm_vcpu *vcpu);
+bool kvm_cond_match(u32 flags, u32 cond);
/*
* Return the SPSR for the specified mode of the virtual CPU.
diff --git a/arch/arm/kvm/Makefile b/arch/arm/kvm/Makefile
index e69a8e1..68f05b9 100644
--- a/arch/arm/kvm/Makefile
+++ b/arch/arm/kvm/Makefile
@@ -12,6 +12,6 @@ obj-$(CONFIG_KVM_ARM_HOST) += init.o interrupts.o exports.o
kvm-arm-y += $(addprefix ../../../virt/kvm/, kvm_main.o coalesced_mmio.o)
-kvm-arm-y += arm.o guest.o mmu.o emulate.o
+kvm-arm-y += arm.o guest.o mmu.o emulate.o kvm_cond_match.o
obj-$(CONFIG_KVM) += kvm-arm.o
diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
index a6cf02b..1724657 100644
--- a/arch/arm/kvm/arm.c
+++ b/arch/arm/kvm/arm.c
@@ -414,6 +414,9 @@ static inline int handle_exit(struct kvm_vcpu *vcpu, struct kvm_run *run,
BUG();
}
+ if (kvm_should_not_have_trapped(vcpu))
+ return 0;
+
return arm_exit_handlers[hsr_ec](vcpu, run);
}
diff --git a/arch/arm/kvm/emulate.c b/arch/arm/kvm/emulate.c
index bd2c3dc..11e2dab 100644
--- a/arch/arm/kvm/emulate.c
+++ b/arch/arm/kvm/emulate.c
@@ -659,3 +659,44 @@ int kvm_emulate_mmio_ls(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
*vcpu_reg(vcpu, 15) += 4;
return 0;
}
+
+/* Some implementations may not check condition codes before trapping! */
+bool kvm_should_not_have_trapped(struct kvm_vcpu *vcpu)
+{
+ unsigned long spsr, cond, flags;
+
+ /*
+ * Exception Code 0 can only happen if we set HCR.TGE to 1, to
+ * catch undefined instructions, and then we won't get past
+ * the arm_exit_handlers test anyway.
+ */
+ BUG_ON(((vcpu->arch.hsr & HSR_EC) >> HSR_EC_SHIFT) == 0);
+
+ /* Top two bits non-zero? Unconditional. */
+ if (vcpu->arch.hsr >> 30)
+ return false;
+
+ spsr = *vcpu_spsr(vcpu);
+
+ /* Is condition field valid? */
+ if ((vcpu->arch.hsr & HSR_CV) >> HSR_CV_SHIFT)
+ cond = (vcpu->arch.hsr & HSR_COND) >> HSR_COND_SHIFT;
+ else {
+ /* This can happen in Thumb mode: examine IT state. */
+ unsigned long it;
+
+ it = ((spsr >> 8) & 0xFC)
+ | ((spsr >> 25) & 0x3);
+
+ /* it == 0 => unconditional. */
+ if (it == 0)
+ return false;
+
+ /* The cond for this insn works out as the top 4 bits. */
+ cond = (it >> 4);
+ }
+
+ flags = spsr & ~0x07FFFFFF;
+
+ return !kvm_cond_match(flags, cond);
+}
diff --git a/arch/arm/kvm/kvm_cond_match.S b/arch/arm/kvm/kvm_cond_match.S
new file mode 100644
index 0000000..cf48786
--- /dev/null
+++ b/arch/arm/kvm/kvm_cond_match.S
@@ -0,0 +1,54 @@
+#include <linux/linkage.h>
+
+/* extern bool kvm_cond_match(u32 flags, u32 cond); */
+ENTRY(kvm_cond_match)
+.arm
+ /* First, set our condition flags to the arg. */
+ mrs r2, cpsr
+ and r2, r2, #0x07FFFFFF
+ orr r2, r2, r0
+ msr cpsr, r2
+
+ /* Now, jump to table depending on cond, return via there. */
+ mov r0, #0
+ add r2, r0, r1, LSL #3
+ sub r2, #4
+ add pc, r2
+
+/* This is "mov<cond> r0, #1" */
+#define COND_MOVEQ_R0_1(cond) .word ((cond << 28) | 0x03a00001)
+
+cond_table:
+ COND_MOVEQ_R0_1(0)
+ mov pc, lr
+ COND_MOVEQ_R0_1(1)
+ mov pc, lr
+ COND_MOVEQ_R0_1(2)
+ mov pc, lr
+ COND_MOVEQ_R0_1(3)
+ mov pc, lr
+ COND_MOVEQ_R0_1(4)
+ mov pc, lr
+ COND_MOVEQ_R0_1(5)
+ mov pc, lr
+ COND_MOVEQ_R0_1(6)
+ mov pc, lr
+ COND_MOVEQ_R0_1(7)
+ mov pc, lr
+ COND_MOVEQ_R0_1(8)
+ mov pc, lr
+ COND_MOVEQ_R0_1(9)
+ mov pc, lr
+ COND_MOVEQ_R0_1(10)
+ mov pc, lr
+ COND_MOVEQ_R0_1(11)
+ mov pc, lr
+ COND_MOVEQ_R0_1(12)
+ mov pc, lr
+ COND_MOVEQ_R0_1(13)
+ mov pc, lr
+ COND_MOVEQ_R0_1(14)
+ mov pc, lr
+ COND_MOVEQ_R0_1(15)
+ mov pc, lr
+ENDPROC(kvm_cond_match)
