Re: [PATCH 28/59] KVM: arm64: nv: Respect the virtual HCR_EL2.NV1 bit setting

Alexandru Elisei
2019-07-02T16:32:21Z

On 6/21/19 10:38 AM, Marc Zyngier wrote:
> From: Jintack Lim <jintack@cs.columbia.edu>
>
> Forward ELR_EL1, SPSR_EL1 and VBAR_EL1 traps to the virtual EL2 if the
> virtual HCR_EL2.NV bit is set.
HCR_EL2.NV1?
>
> This is for recursive nested virtualization.
>
> Signed-off-by: Jintack Lim <jintack@cs.columbia.edu>
> Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
> ---
> arch/arm64/include/asm/kvm_arm.h | 1 +
> arch/arm64/kvm/sys_regs.c | 19 +++++++++++++++++--
> 2 files changed, 18 insertions(+), 2 deletions(-)
>
> diff --git a/arch/arm64/include/asm/kvm_arm.h b/arch/arm64/include/asm/kvm_arm.h
> index d21486274eeb..55f4525c112c 100644
> --- a/arch/arm64/include/asm/kvm_arm.h
> +++ b/arch/arm64/include/asm/kvm_arm.h
> @@ -24,6 +24,7 @@
>
> /* Hyp Configuration Register (HCR) bits */
> #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 0f74b9277a86..beadebcfc888 100644
> --- a/arch/arm64/kvm/sys_regs.c
> +++ b/arch/arm64/kvm/sys_regs.c
> @@ -473,8 +473,10 @@ static bool access_vm_reg(struct kvm_vcpu *vcpu,
> if (el12_reg(p) && forward_nv_traps(vcpu))
> return false;
>
> - if (!el12_reg(p) && forward_vm_traps(vcpu, p))
> - return kvm_inject_nested_sync(vcpu, kvm_vcpu_get_hsr(vcpu));
> + if (!el12_reg(p) && forward_vm_traps(vcpu, p)) {
> + kvm_inject_nested_sync(vcpu, kvm_vcpu_get_hsr(vcpu));
> + return false;
> + }
>
> BUG_ON(!vcpu_mode_el2(vcpu) && !p->is_write);
>
> @@ -1643,6 +1645,13 @@ static bool access_sp_el1(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)
Why the struct sys_reg_params *p argument? It isn't used by the function.
> +{
> + return forward_traps(vcpu, HCR_NV1);
> +}
> +
> static bool access_elr(struct kvm_vcpu *vcpu,
> struct sys_reg_params *p,
> const struct sys_reg_desc *r)
> @@ -1650,6 +1659,9 @@ 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->arch.ctxt.gp_regs.elr_el1 = p->regval;
> else
> @@ -1665,6 +1677,9 @@ 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->arch.ctxt.gp_regs.spsr[KVM_SPSR_EL1] = p->regval;
> else

The commit message mentions VBAR_EL1, but there's no change related to it.
Parhaps you're missing this (build tested only):

diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index bd21f0f45a86..082dc31ff533 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -401,6 +401,12 @@ static bool el12_reg(struct sys_reg_params *p)
return (p->Op1 == 5);
}

+/* 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);
+}
+
static bool access_rw(struct kvm_vcpu *vcpu,
struct sys_reg_params *p,
const struct sys_reg_desc *r)
@@ -408,6 +414,10 @@ static bool access_rw(struct kvm_vcpu *vcpu,
if (el12_reg(p) && forward_nv_traps(vcpu))
return false;

+       if (sys_reg(p->Op0, p->Op1, p->CRn, p->CRm, p->Op2) == SYS_VBAR_EL1 &&
+           forward_nv1_traps(vcpu, p))
+               return false;
+
if (p->is_write)
vcpu_write_sys_reg(vcpu, p->regval, r->reg);
else
@@ -1794,12 +1804,6 @@ static bool forward_ttlb_traps(struct kvm_vcpu *vcpu)
return forward_traps(vcpu, HCR_TTLB);
}

-/* 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);
-}
-
static bool access_elr(struct kvm_vcpu *vcpu,
struct sys_reg_params *p,
const struct sys_reg_desc *r)