[PATCH v6 39/64] KVM: arm64: nv: Set a handler for the system instruction traps

Marc Zyngier
2022-01-28T13:11:33Z

From: Jintack Lim <jintack.lim@linaro.org>

When HCR.NV bit is set, execution of the EL2 translation regime address
aranslation instructions and TLB maintenance instructions are trapped to
EL2. In addition, execution of the EL1 translation regime address
aranslation instructions and TLB maintenance instructions that are only
accessible from EL2 and above are trapped to EL2. In these cases,
ESR_EL2.EC will be set to 0x18.

Rework the system instruction emulation framework to handle potentially
all system instruction traps other than MSR/MRS instructions. Those
system instructions would be AT and TLBI instructions controlled by
HCR_EL2.NV, AT, and TTLB bits.

Signed-off-by: Jintack Lim <jintack.lim@linaro.org>
[maz: squashed two patches together, redispatched various bits around]
Signed-off-by: Marc Zyngier <maz@kernel.org>
---
arch/arm64/include/asm/kvm_host.h | 4 +--
arch/arm64/kvm/handle_exit.c | 2 +-
arch/arm64/kvm/sys_regs.c | 48 +++++++++++++++++++++++++------
3 files changed, 42 insertions(+), 12 deletions(-)

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index a15183d0e1bf..0b887364f994 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -407,7 +407,7 @@ struct kvm_vcpu_arch {
/*
* Guest registers we preserve during guest debugging.
*
- * These shadow registers are updated by the kvm_handle_sys_reg
+ * These shadow registers are updated by the kvm_handle_sys
* trap handler if the guest accesses or updates them while we
* are using guest debug.
*/
@@ -724,7 +724,7 @@ int kvm_handle_cp14_32(struct kvm_vcpu *vcpu);
int kvm_handle_cp14_64(struct kvm_vcpu *vcpu);
int kvm_handle_cp15_32(struct kvm_vcpu *vcpu);
int kvm_handle_cp15_64(struct kvm_vcpu *vcpu);
-int kvm_handle_sys_reg(struct kvm_vcpu *vcpu);
+int kvm_handle_sys(struct kvm_vcpu *vcpu);

void kvm_reset_sys_regs(struct kvm_vcpu *vcpu);

diff --git a/arch/arm64/kvm/handle_exit.c b/arch/arm64/kvm/handle_exit.c
index 867de65eb766..d135fc7e6883 100644
--- a/arch/arm64/kvm/handle_exit.c
+++ b/arch/arm64/kvm/handle_exit.c
@@ -236,7 +236,7 @@ static exit_handle_fn arm_exit_handlers[] = {
[ESR_ELx_EC_SMC32] = handle_smc,
[ESR_ELx_EC_HVC64] = handle_hvc,
[ESR_ELx_EC_SMC64] = handle_smc,
- [ESR_ELx_EC_SYS64] = kvm_handle_sys_reg,
+ [ESR_ELx_EC_SYS64] = kvm_handle_sys,
[ESR_ELx_EC_SVE] = handle_sve,
[ESR_ELx_EC_ERET] = kvm_handle_eret,
[ESR_ELx_EC_IABT_LOW] = kvm_handle_guest_abort,
diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index 5e8876177ce6..f669618f966b 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -1771,10 +1771,6 @@ static bool access_spsr_el2(struct kvm_vcpu *vcpu,
* more demanding guest...
*/
static const struct sys_reg_desc sys_reg_descs[] = {
- { SYS_DESC(SYS_DC_ISW), access_dcsw },
- { SYS_DESC(SYS_DC_CSW), access_dcsw },
- { SYS_DESC(SYS_DC_CISW), access_dcsw },
-
DBG_BCR_BVR_WCR_WVR_EL1(0),
DBG_BCR_BVR_WCR_WVR_EL1(1),
{ SYS_DESC(SYS_MDCCINT_EL1), trap_debug_regs, reset_val, MDCCINT_EL1, 0 },
@@ -2240,6 +2236,14 @@ static const struct sys_reg_desc sys_reg_descs[] = {
EL2_REG(SP_EL2, NULL, reset_unknown, 0),
};

+#define SYS_INSN_TO_DESC(insn, access_fn, forward_fn) \
+ { SYS_DESC((insn)), (access_fn), NULL, 0, 0, NULL, NULL, (forward_fn) }
+static struct sys_reg_desc sys_insn_descs[] = {
+ { SYS_DESC(SYS_DC_ISW), access_dcsw },
+ { SYS_DESC(SYS_DC_CSW), access_dcsw },
+ { SYS_DESC(SYS_DC_CISW), access_dcsw },
+};
+
static bool trap_dbgdidr(struct kvm_vcpu *vcpu,
struct sys_reg_params *p,
const struct sys_reg_desc *r)
@@ -2786,6 +2790,24 @@ static int emulate_sys_reg(struct kvm_vcpu *vcpu,
return 1;
}

+static int emulate_sys_instr(struct kvm_vcpu *vcpu, struct sys_reg_params *p)
+{
+ const struct sys_reg_desc *r;
+
+ /* Search from the system instruction table. */
+ r = find_reg(p, sys_insn_descs, ARRAY_SIZE(sys_insn_descs));
+
+ if (likely(r)) {
+ perform_access(vcpu, p, r);
+ } else {
+ kvm_err("Unsupported guest sys instruction at: %lx\n",
+ *vcpu_pc(vcpu));
+ print_sys_reg_instr(p);
+ kvm_inject_undefined(vcpu);
+ }
+ return 1;
+}
+
/**
* kvm_reset_sys_regs - sets system registers to reset value
* @vcpu: The VCPU pointer
@@ -2803,10 +2825,11 @@ void kvm_reset_sys_regs(struct kvm_vcpu *vcpu)
}

/**
- * kvm_handle_sys_reg -- handles a mrs/msr trap on a guest sys_reg access
+ * kvm_handle_sys-- handles a system instruction or mrs/msr instruction trap
+ on a guest execution
* @vcpu: The VCPU pointer
*/
-int kvm_handle_sys_reg(struct kvm_vcpu *vcpu)
+int kvm_handle_sys(struct kvm_vcpu *vcpu)
{
struct sys_reg_params params;
unsigned long esr = kvm_vcpu_get_esr(vcpu);
@@ -2818,10 +2841,16 @@ int kvm_handle_sys_reg(struct kvm_vcpu *vcpu)
params = esr_sys64_to_params(esr);
params.regval = vcpu_get_reg(vcpu, Rt);

- ret = emulate_sys_reg(vcpu, &params);
+ if (params.Op0 == 1) {
+ /* System instructions */
+ ret = emulate_sys_instr(vcpu, &params);
+ } else {
+ /* MRS/MSR instructions */
+ ret = emulate_sys_reg(vcpu, &params);
+ if (!params.is_write)
+ vcpu_set_reg(vcpu, Rt, params.regval);
+ }

- if (!params.is_write)
- vcpu_set_reg(vcpu, Rt, params.regval);
return ret;
}

@@ -3237,6 +3266,7 @@ void kvm_sys_reg_table_init(void)
BUG_ON(check_sysreg_table(cp15_regs, ARRAY_SIZE(cp15_regs), true));
BUG_ON(check_sysreg_table(cp15_64_regs, ARRAY_SIZE(cp15_64_regs), true));
BUG_ON(check_sysreg_table(invariant_sys_regs, ARRAY_SIZE(invariant_sys_regs), false));
+ BUG_ON(check_sysreg_table(sys_insn_descs, ARRAY_SIZE(sys_insn_descs), false));

/* We abuse the reset function to overwrite the table itself. */
for (i = 0; i < ARRAY_SIZE(invariant_sys_regs); i++)