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Subject[RFC PATCH v2 34/38] KVM: arm64: Respect the virtual HCR_EL2.NV bit setting
Date
Forward traps due to HCR_EL2.NV bit to the virtual EL2 if they are not
coming from the virtual EL2 and the virtual HCR_EL2.NV bit is set.

This is for recursive nested virtualization.

Signed-off-by: Jintack Lim <jintack.lim@linaro.org>
---
arch/arm64/include/asm/kvm_arm.h | 1 +
arch/arm64/include/asm/kvm_coproc.h | 1 +
arch/arm64/kvm/handle_exit.c | 13 +++++++++++++
arch/arm64/kvm/sys_regs.c | 22 ++++++++++++++++++++++
4 files changed, 37 insertions(+)

diff --git a/arch/arm64/include/asm/kvm_arm.h b/arch/arm64/include/asm/kvm_arm.h
index 6e99978..aeaac4e 100644
--- a/arch/arm64/include/asm/kvm_arm.h
+++ b/arch/arm64/include/asm/kvm_arm.h
@@ -23,6 +23,7 @@
#include <asm/types.h>

/* Hyp Configuration Register (HCR) bits */
+#define HCR_NV (UL(1) << 42)
#define HCR_E2H (UL(1) << 34)
#define HCR_ID (UL(1) << 33)
#define HCR_CD (UL(1) << 32)
diff --git a/arch/arm64/include/asm/kvm_coproc.h b/arch/arm64/include/asm/kvm_coproc.h
index 1b3d21b..6223df6 100644
--- a/arch/arm64/include/asm/kvm_coproc.h
+++ b/arch/arm64/include/asm/kvm_coproc.h
@@ -44,6 +44,7 @@ void kvm_register_target_sys_reg_table(unsigned int target,
int kvm_handle_cp15_32(struct kvm_vcpu *vcpu, struct kvm_run *run);
int kvm_handle_cp15_64(struct kvm_vcpu *vcpu, struct kvm_run *run);
int kvm_handle_sys(struct kvm_vcpu *vcpu, struct kvm_run *run);
+bool forward_nv_traps(struct kvm_vcpu *vcpu);

#define kvm_coproc_table_init kvm_sys_reg_table_init
void kvm_sys_reg_table_init(void);
diff --git a/arch/arm64/kvm/handle_exit.c b/arch/arm64/kvm/handle_exit.c
index d4e7b2b..fccd9d6 100644
--- a/arch/arm64/kvm/handle_exit.c
+++ b/arch/arm64/kvm/handle_exit.c
@@ -61,6 +61,12 @@ static int handle_smc(struct kvm_vcpu *vcpu, struct kvm_run *run)
{
int ret;

+ /*
+ * Forward this trapped smc instruction to the virtual EL2.
+ */
+ if (forward_nv_traps(vcpu) && (vcpu_sys_reg(vcpu, HCR_EL2) & HCR_TSC))
+ return kvm_inject_nested_sync(vcpu, kvm_vcpu_get_hsr(vcpu));
+
/* If imm is non-zero, it's not defined */
if (kvm_vcpu_hvc_get_imm(vcpu)) {
kvm_inject_undefined(vcpu);
@@ -197,6 +203,13 @@ static int kvm_handle_eret(struct kvm_vcpu *vcpu, struct kvm_run *run)
vcpu_el2_sreg(vcpu, SPSR_EL2));

/*
+ * Forward this trap to the virtual EL2 if the virtual HCR_EL2.NV
+ * bit is set.
+ */
+ if (forward_nv_traps(vcpu))
+ return kvm_inject_nested_sync(vcpu, kvm_vcpu_get_hsr(vcpu));
+
+ /*
* Note that the current exception level is always the virtual EL2,
* since we set HCR_EL2.NV bit only when entering the virtual EL2.
*/
diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index 910b50d..4fd7090 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -939,6 +939,14 @@ static bool access_cntp_cval(struct kvm_vcpu *vcpu,
return true;
}

+/* This function is to support the recursive nested virtualization */
+bool forward_nv_traps(struct kvm_vcpu *vcpu)
+{
+ if (!vcpu_mode_el2(vcpu) && (vcpu_sys_reg(vcpu, HCR_EL2) & HCR_NV))
+ return true;
+ return false;
+}
+
static inline void access_rw(struct sys_reg_params *p, u64 *sysreg)
{
if (!p->is_write)
@@ -977,6 +985,13 @@ static bool trap_el2_regs(struct kvm_vcpu *vcpu,
{
u64 *sys_reg;

+ /*
+ * Forward this trap to the virtual EL2 if the virtual HCR_EL2.NV
+ * bit is set.
+ */
+ if (forward_nv_traps(vcpu))
+ return kvm_inject_nested_sync(vcpu, kvm_vcpu_get_hsr(vcpu));
+
sys_reg = get_special_reg(vcpu, p);
if (!sys_reg)
sys_reg = &vcpu_sys_reg(vcpu, r->reg);
@@ -1914,6 +1929,13 @@ static int emulate_sys_instr(struct kvm_vcpu *vcpu,
{
int ret = 0;

+ /*
+ * Forward this trap to the virtual EL2 if the virtual HCR_EL2.NV
+ * bit is set.
+ */
+ if (forward_nv_traps(vcpu))
+ return kvm_inject_nested_sync(vcpu, kvm_vcpu_get_hsr(vcpu));
+
/* TLB maintenance instructions*/
if (params->CRn == 0b1000)
ret = emulate_tlbi(vcpu, params);
--
1.9.1
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