Subject: [RFC PATCH v2 28/38] KVM: arm64: Emulate EL12 register accesses from the virtual EL2

From: [email-masked] (Christoffer Dall)
Date: Mon, 31 Jul 2017 10:44:11 +0200

On Tue, Jul 18, 2017 at 11:58:54AM -0500, Jintack Lim wrote:
> With HCR_EL2.NV bit set, accesses to EL12 registers in the virtual EL2
> trap to EL2. Handle those traps just like we do for EL1 registers.
> 
> One exception is CNTKCTL_EL12. We don't trap on CNTKCTL_EL1 for non-VHE
> virtual EL2 because we don't have to. However, accessing CNTKCTL_EL12
> will trap since it's one of the EL12 registers controlled by HCR_EL2.NV
> bit.  Therefore, add a handler for it and don't treat it as a
> non-trap-registers when preparing a shadow context.

I'm sorry, I don't remember the details, and I don't understand from
this paragraph what the difference between CNTKCTL_EL12 and the other
EL12 registers is?

> 
> Move EL12 system register macros to a common place to reuse them.
> 
> Signed-off-by: Jintack Lim <[email-masked]>
> ---
>  arch/arm64/include/asm/kvm_hyp.h | 24 ------------------------
>  arch/arm64/include/asm/sysreg.h  | 24 ++++++++++++++++++++++++
>  arch/arm64/kvm/context.c         |  7 +++++++
>  arch/arm64/kvm/sys_regs.c        | 25 +++++++++++++++++++++++++
>  4 files changed, 56 insertions(+), 24 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/kvm_hyp.h b/arch/arm64/include/asm/kvm_hyp.h
> index 4572a9b..353b895 100644
> --- a/arch/arm64/include/asm/kvm_hyp.h
> +++ b/arch/arm64/include/asm/kvm_hyp.h
> @@ -73,30 +73,6 @@
>  #define read_sysreg_el1(r)	read_sysreg_elx(r, _EL1, _EL12)
>  #define write_sysreg_el1(v,r)	write_sysreg_elx(v, r, _EL1, _EL12)
>  
> -/* The VHE specific system registers and their encoding */
> -#define sctlr_EL12              sys_reg(3, 5, 1, 0, 0)
> -#define cpacr_EL12              sys_reg(3, 5, 1, 0, 2)
> -#define ttbr0_EL12              sys_reg(3, 5, 2, 0, 0)
> -#define ttbr1_EL12              sys_reg(3, 5, 2, 0, 1)
> -#define tcr_EL12                sys_reg(3, 5, 2, 0, 2)
> -#define afsr0_EL12              sys_reg(3, 5, 5, 1, 0)
> -#define afsr1_EL12              sys_reg(3, 5, 5, 1, 1)
> -#define esr_EL12                sys_reg(3, 5, 5, 2, 0)
> -#define far_EL12                sys_reg(3, 5, 6, 0, 0)
> -#define mair_EL12               sys_reg(3, 5, 10, 2, 0)
> -#define amair_EL12              sys_reg(3, 5, 10, 3, 0)
> -#define vbar_EL12               sys_reg(3, 5, 12, 0, 0)
> -#define contextidr_EL12         sys_reg(3, 5, 13, 0, 1)
> -#define cntkctl_EL12            sys_reg(3, 5, 14, 1, 0)
> -#define cntp_tval_EL02          sys_reg(3, 5, 14, 2, 0)
> -#define cntp_ctl_EL02           sys_reg(3, 5, 14, 2, 1)
> -#define cntp_cval_EL02          sys_reg(3, 5, 14, 2, 2)
> -#define cntv_tval_EL02          sys_reg(3, 5, 14, 3, 0)
> -#define cntv_ctl_EL02           sys_reg(3, 5, 14, 3, 1)
> -#define cntv_cval_EL02          sys_reg(3, 5, 14, 3, 2)
> -#define spsr_EL12               sys_reg(3, 5, 4, 0, 0)
> -#define elr_EL12                sys_reg(3, 5, 4, 0, 1)
> -
>  /**
>   * hyp_alternate_select - Generates patchable code sequences that are
>   * used to switch between two implementations of a function, depending
> diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h
> index b01c608..b8d4d0c 100644
> --- a/arch/arm64/include/asm/sysreg.h
> +++ b/arch/arm64/include/asm/sysreg.h
> @@ -338,6 +338,30 @@
>  #define SYS_CNTVOFF_EL2			sys_reg(3, 4, 14, 0, 3)
>  #define SYS_CNTHCTL_EL2			sys_reg(3, 4, 14, 1, 0)
>  
> +/* The VHE specific system registers and their encoding */
> +#define sctlr_EL12              sys_reg(3, 5, 1, 0, 0)
> +#define cpacr_EL12              sys_reg(3, 5, 1, 0, 2)
> +#define ttbr0_EL12              sys_reg(3, 5, 2, 0, 0)
> +#define ttbr1_EL12              sys_reg(3, 5, 2, 0, 1)
> +#define tcr_EL12                sys_reg(3, 5, 2, 0, 2)
> +#define afsr0_EL12              sys_reg(3, 5, 5, 1, 0)
> +#define afsr1_EL12              sys_reg(3, 5, 5, 1, 1)
> +#define esr_EL12                sys_reg(3, 5, 5, 2, 0)
> +#define far_EL12                sys_reg(3, 5, 6, 0, 0)
> +#define mair_EL12               sys_reg(3, 5, 10, 2, 0)
> +#define amair_EL12              sys_reg(3, 5, 10, 3, 0)
> +#define vbar_EL12               sys_reg(3, 5, 12, 0, 0)
> +#define contextidr_EL12         sys_reg(3, 5, 13, 0, 1)
> +#define cntkctl_EL12            sys_reg(3, 5, 14, 1, 0)
> +#define cntp_tval_EL02          sys_reg(3, 5, 14, 2, 0)
> +#define cntp_ctl_EL02           sys_reg(3, 5, 14, 2, 1)
> +#define cntp_cval_EL02          sys_reg(3, 5, 14, 2, 2)
> +#define cntv_tval_EL02          sys_reg(3, 5, 14, 3, 0)
> +#define cntv_ctl_EL02           sys_reg(3, 5, 14, 3, 1)
> +#define cntv_cval_EL02          sys_reg(3, 5, 14, 3, 2)
> +#define spsr_EL12               sys_reg(3, 5, 4, 0, 0)
> +#define elr_EL12                sys_reg(3, 5, 4, 0, 1)
> +
>  #define SYS_SP_EL2			sys_reg(3, 6, 4, 1, 0)
>  
>  /* Common SCTLR_ELx flags. */
> diff --git a/arch/arm64/kvm/context.c b/arch/arm64/kvm/context.c
> index e1bc753..f3d3398 100644
> --- a/arch/arm64/kvm/context.c
> +++ b/arch/arm64/kvm/context.c
> @@ -121,6 +121,13 @@ static void copy_shadow_non_trap_el1_state(struct kvm_vcpu *vcpu, bool setup)
>  	for (i = 0; i < ARRAY_SIZE(el1_non_trap_regs); i++) {
>  		const int sr = el1_non_trap_regs[i];
>  
> +		/*
> +		 * We trap on cntkctl_el12 accesses from virtual EL2 as suppose

as opposed to ?

> +		 * to not trapping on cntlctl_el1 accesses.
> +		 */
> +		if (vcpu_el2_e2h_is_set(vcpu) && sr == CNTKCTL_EL1)
> +			continue;
> +

If the guest can still access CNTHCTL_EL2 via the CNTKCTL_EL1 system
regsiter access encoding without trapping, why is the don't we need to
copy this here?

Is the point that for a VHE guest, we don't copy vcpu_sys_reg(vcpu,
CNTKCTL_EL1) to the hardware CNTKCTL_EL1, but we copy vcpu_sys_reg(vcpu,
CNTHCTL_EL2) into CNTKCTL_EL1 during the world switch instead?

Thanks,
-Christoffer

>  		if (setup)
>  			s_sys_regs[sr] = vcpu_sys_reg(vcpu, sr);
>  		else
> diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
> index b3e0cb8..2aa922c 100644
> --- a/arch/arm64/kvm/sys_regs.c
> +++ b/arch/arm64/kvm/sys_regs.c
> @@ -905,6 +905,14 @@ static inline void access_rw(struct sys_reg_params *p, u64 *sysreg)
>  		*sysreg = p->regval;
>  }
>  
> +static bool access_cntkctl_el12(struct kvm_vcpu *vcpu,
> +			 struct sys_reg_params *p,
> +			 const struct sys_reg_desc *r)
> +{
> +	access_rw(p, &vcpu_sys_reg(vcpu, r->reg));
> +	return true;
> +}
> +
>  static u64 *get_special_reg(struct kvm_vcpu *vcpu, struct sys_reg_params *p)
>  {
>  	u64 reg = sys_reg(p->Op0, p->Op1, p->CRn, p->CRm, p->Op2);
> @@ -1201,6 +1209,23 @@ static bool access_cpacr(struct kvm_vcpu *vcpu,
>  	{ SYS_DESC(SYS_CNTVOFF_EL2), trap_el2_regs, reset_val, CNTVOFF_EL2, 0 },
>  	{ SYS_DESC(SYS_CNTHCTL_EL2), trap_el2_regs, reset_val, CNTHCTL_EL2, 0 },
>  
> +	{ SYS_DESC(sctlr_EL12), access_vm_reg, reset_val, SCTLR_EL1, 0x00C50078 },
> +	{ SYS_DESC(cpacr_EL12), access_cpacr, reset_val, CPACR_EL1, 0 },
> +	{ SYS_DESC(ttbr0_EL12), access_vm_reg, reset_unknown, TTBR0_EL1 },
> +	{ SYS_DESC(ttbr1_EL12), access_vm_reg, reset_unknown, TTBR1_EL1 },
> +	{ SYS_DESC(tcr_EL12), access_vm_reg, reset_val, TCR_EL1, 0 },
> +	{ SYS_DESC(spsr_EL12), access_spsr},
> +	{ SYS_DESC(elr_EL12), access_elr},
> +	{ SYS_DESC(afsr0_EL12), access_vm_reg, reset_unknown, AFSR0_EL1 },
> +	{ SYS_DESC(afsr1_EL12), access_vm_reg, reset_unknown, AFSR1_EL1 },
> +	{ SYS_DESC(esr_EL12), access_vm_reg, reset_unknown, ESR_EL1 },
> +	{ SYS_DESC(far_EL12), access_vm_reg, reset_unknown, FAR_EL1 },
> +	{ SYS_DESC(mair_EL12), access_vm_reg, reset_unknown, MAIR_EL1 },
> +	{ SYS_DESC(amair_EL12), access_vm_reg, reset_amair_el1, AMAIR_EL1 },
> +	{ SYS_DESC(vbar_EL12), access_vbar, reset_val, VBAR_EL1, 0 },
> +	{ SYS_DESC(contextidr_EL12), access_vm_reg, reset_val, CONTEXTIDR_EL1, 0 },
> +	{ SYS_DESC(cntkctl_EL12), access_cntkctl_el12, reset_val, CNTKCTL_EL1, 0 },
> +
>  	{ SYS_DESC(SYS_SP_EL2), NULL, reset_special, SP_EL2, 0},
>  };
>  
> -- 
> 1.9.1
>