Re: [PATCH v5 31/69] KVM: arm64: nv: Respect the virtual HCR_EL2.NV1 bit setting

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On 30-11-2021 01:31 am, Marc Zyngier wrote:
From: Jintack Lim <jintack@xxxxxxxxxxxxxxx>

Forward ELR_EL1, SPSR_EL1 and VBAR_EL1 traps to the virtual EL2 if the
virtual HCR_EL2.NV bit is set.

This is for recursive nested virtualization.

Signed-off-by: Jintack Lim <jintack@xxxxxxxxxxxxxxx>
Signed-off-by: Marc Zyngier <maz@xxxxxxxxxx>
---
  arch/arm64/include/asm/kvm_arm.h |  1 +
  arch/arm64/kvm/sys_regs.c        | 28 +++++++++++++++++++++++++++-
  2 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/include/asm/kvm_arm.h b/arch/arm64/include/asm/kvm_arm.h
index 9759bc893a51..68af5509e4b0 100644
--- a/arch/arm64/include/asm/kvm_arm.h
+++ b/arch/arm64/include/asm/kvm_arm.h
@@ -20,6 +20,7 @@
  #define HCR_AMVOFFEN	(UL(1) << 51)
  #define HCR_FIEN	(UL(1) << 47)
  #define HCR_FWB		(UL(1) << 46)
+#define HCR_NV1		(UL(1) << 43)
  #define HCR_NV		(UL(1) << 42)
  #define HCR_API		(UL(1) << 41)
  #define HCR_APK		(UL(1) << 40)
diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index e96877fc3b2a..511e06b6f603 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -288,6 +288,22 @@ static bool access_rw(struct kvm_vcpu *vcpu,
  	return true;
  }
+/* This function is to support the recursive nested virtualization */
+static bool forward_nv1_traps(struct kvm_vcpu *vcpu, struct sys_reg_params *p)
+{
+	return forward_traps(vcpu, HCR_NV1);
+}
+

Shall we move this helper to emulate-nested.c?

+static bool access_vbar_el1(struct kvm_vcpu *vcpu,
+			    struct sys_reg_params *p,
+			    const struct sys_reg_desc *r)
+{
+	if (forward_nv1_traps(vcpu, p))
+		return false;
+
+	return access_rw(vcpu, p, r);
+}
+
  static bool access_sctlr_el2(struct kvm_vcpu *vcpu,
  			     struct sys_reg_params *p,
  			     const struct sys_reg_desc *r)
@@ -1682,6 +1698,7 @@ static bool access_sp_el1(struct kvm_vcpu *vcpu,
  	return true;
  }
+
  static bool access_elr(struct kvm_vcpu *vcpu,
  		       struct sys_reg_params *p,
  		       const struct sys_reg_desc *r)
@@ -1689,6 +1706,9 @@ static bool access_elr(struct kvm_vcpu *vcpu,
  	if (el12_reg(p) && forward_nv_traps(vcpu))
  		return false;
+ if (!el12_reg(p) && forward_nv1_traps(vcpu, p))
+		return false;
+
  	if (p->is_write)
  		vcpu_write_sys_reg(vcpu, p->regval, ELR_EL1);
  	else
@@ -1704,6 +1724,9 @@ static bool access_spsr(struct kvm_vcpu *vcpu,
  	if (el12_reg(p) && forward_nv_traps(vcpu))
  		return false;
+ if (!el12_reg(p) && forward_nv1_traps(vcpu, p))
+		return false;
+
  	if (p->is_write)
  		__vcpu_sys_reg(vcpu, SPSR_EL1) = p->regval;
  	else
@@ -1719,6 +1742,9 @@ static bool access_spsr_el2(struct kvm_vcpu *vcpu,
  	if (el12_reg(p) && forward_nv_traps(vcpu))
  		return false;
+ if (!el12_reg(p) && forward_nv1_traps(vcpu, p))
+		return false;
+
  	if (p->is_write)
  		vcpu_write_sys_reg(vcpu, p->regval, SPSR_EL2);
  	else
@@ -1927,7 +1953,7 @@ static const struct sys_reg_desc sys_reg_descs[] = {
  	{ SYS_DESC(SYS_LORC_EL1), trap_loregion },
  	{ SYS_DESC(SYS_LORID_EL1), trap_loregion },
- { SYS_DESC(SYS_VBAR_EL1), access_rw, reset_val, VBAR_EL1, 0 },
+	{ SYS_DESC(SYS_VBAR_EL1), access_vbar_el1, reset_val, VBAR_EL1, 0 },
  	{ SYS_DESC(SYS_DISR_EL1), NULL, reset_val, DISR_EL1, 0 },
{ SYS_DESC(SYS_ICC_IAR0_EL1), write_to_read_only },

Thanks,
Ganapat



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