Re: [PATCH v8 40/43] arm64: RME: Provide accurate register list

[Gavin Shan <gshan@redhat.com>]

On 4/16/25 11:42 PM, Steven Price wrote:
> From: Jean-Philippe Brucker <jean-philippe@linaro.org>
> 
> Userspace can set a few registers with KVM_SET_ONE_REG (9 GP registers
> at runtime, and 3 system registers during initialization). Update the
> register list returned by KVM_GET_REG_LIST.
> 
> Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
> Signed-off-by: Steven Price <steven.price@arm.com>
> ---
> Changes since v7:
>   * Reworked on upstream changes.
> ---
>   arch/arm64/kvm/guest.c      | 19 ++++++++++++++-----
>   arch/arm64/kvm/hypercalls.c |  4 ++--
>   arch/arm64/kvm/sys_regs.c   | 28 ++++++++++++++++++++++------
>   3 files changed, 38 insertions(+), 13 deletions(-)
> 

With below nitpicks addressed:

Reviewed-by: Gavin Shan <gshan@redhat.com>

> diff --git a/arch/arm64/kvm/guest.c b/arch/arm64/kvm/guest.c
> index 1288920fc73d..e9bb7647aa65 100644
> --- a/arch/arm64/kvm/guest.c
> +++ b/arch/arm64/kvm/guest.c
> @@ -618,8 +618,6 @@ static const u64 timer_reg_list[] = {
>   	KVM_REG_ARM_PTIMER_CVAL,
>   };
>   
> -#define NUM_TIMER_REGS ARRAY_SIZE(timer_reg_list)
> -
>   static bool is_timer_reg(u64 index)
>   {
>   	switch (index) {
> @@ -634,9 +632,14 @@ static bool is_timer_reg(u64 index)
>   	return false;
>   }
>   
> +static unsigned long num_timer_regs(struct kvm_vcpu *vcpu)
> +{
> +	return kvm_is_realm(vcpu->kvm) ? 0 : ARRAY_SIZE(timer_reg_list);
> +}
> +

static inline unsigned long num_timer_regs(struct kvm_vcpu *vcpu)

>   static int copy_timer_indices(struct kvm_vcpu *vcpu, u64 __user *uindices)
>   {
> -	for (int i = 0; i < NUM_TIMER_REGS; i++) {
> +	for (int i = 0; i < num_timer_regs(vcpu); i++) {
>   		if (put_user(timer_reg_list[i], uindices))
>   			return -EFAULT;
>   		uindices++;

	for (unsigned long i = 0; ...)

> @@ -674,6 +677,9 @@ static unsigned long num_sve_regs(const struct kvm_vcpu *vcpu)
>   	if (!vcpu_has_sve(vcpu) || !kvm_arm_vcpu_sve_finalized(vcpu))
>   		return 0;
>   
> +	if (kvm_is_realm(vcpu->kvm))
> +		return 1; /* KVM_REG_ARM64_SVE_VLS */
> +
>   	return slices * (SVE_NUM_PREGS + SVE_NUM_ZREGS + 1 /* FFR */)
>   		+ 1; /* KVM_REG_ARM64_SVE_VLS */
>   }
> @@ -701,6 +707,9 @@ static int copy_sve_reg_indices(const struct kvm_vcpu *vcpu,
>   		return -EFAULT;
>   	++num_regs;
>   
> +	if (kvm_is_realm(vcpu->kvm))
> +		return num_regs;
> +
>   	for (i = 0; i < slices; i++) {
>   		for (n = 0; n < SVE_NUM_ZREGS; n++) {
>   			reg = KVM_REG_ARM64_SVE_ZREG(n, i);
> @@ -739,7 +748,7 @@ unsigned long kvm_arm_num_regs(struct kvm_vcpu *vcpu)
>   	res += num_sve_regs(vcpu);
>   	res += kvm_arm_num_sys_reg_descs(vcpu);
>   	res += kvm_arm_get_fw_num_regs(vcpu);
> -	res += NUM_TIMER_REGS;
> +	res += num_timer_regs(vcpu);
>   
>   	return res;
>   }
> @@ -773,7 +782,7 @@ int kvm_arm_copy_reg_indices(struct kvm_vcpu *vcpu, u64 __user *uindices)
>   	ret = copy_timer_indices(vcpu, uindices);
>   	if (ret < 0)
>   		return ret;
> -	uindices += NUM_TIMER_REGS;
> +	uindices += num_timer_regs(vcpu);
>   
>   	return kvm_arm_copy_sys_reg_indices(vcpu, uindices);
>   }
> diff --git a/arch/arm64/kvm/hypercalls.c b/arch/arm64/kvm/hypercalls.c
> index 569941eeb3fe..fb2bba0c7e86 100644
> --- a/arch/arm64/kvm/hypercalls.c
> +++ b/arch/arm64/kvm/hypercalls.c
> @@ -412,14 +412,14 @@ void kvm_arm_teardown_hypercalls(struct kvm *kvm)
>   
>   int kvm_arm_get_fw_num_regs(struct kvm_vcpu *vcpu)
>   {
> -	return ARRAY_SIZE(kvm_arm_fw_reg_ids);
> +	return kvm_is_realm(vcpu->kvm) ? 0 : ARRAY_SIZE(kvm_arm_fw_reg_ids);
>   }
>   
>   int kvm_arm_copy_fw_reg_indices(struct kvm_vcpu *vcpu, u64 __user *uindices)
>   {
>   	int i;
>   
> -	for (i = 0; i < ARRAY_SIZE(kvm_arm_fw_reg_ids); i++) {
> +	for (i = 0; i < kvm_arm_get_fw_num_regs(vcpu); i++) {
>   		if (put_user(kvm_arm_fw_reg_ids[i], uindices++))
>   			return -EFAULT;
>   	}
> diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
> index a53a06700867..7d384016d1ba 100644
> --- a/arch/arm64/kvm/sys_regs.c
> +++ b/arch/arm64/kvm/sys_regs.c
> @@ -4960,18 +4960,18 @@ int kvm_arm_sys_reg_set_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg
>   				    sys_reg_descs, ARRAY_SIZE(sys_reg_descs));
>   }
>   
> -static unsigned int num_demux_regs(void)
> +static unsigned int num_demux_regs(struct kvm_vcpu *vcpu)
>   {
> -	return CSSELR_MAX;
> +	return kvm_is_realm(vcpu->kvm) ? 0 : CSSELR_MAX;
>   }
>   

static inline unsigned int num_demux_regs(struct kvm_vcpu *vcpu)

> -static int write_demux_regids(u64 __user *uindices)
> +static int write_demux_regids(struct kvm_vcpu *vcpu, u64 __user *uindices)
>   {
>   	u64 val = KVM_REG_ARM64 | KVM_REG_SIZE_U32 | KVM_REG_ARM_DEMUX;
>   	unsigned int i;
>   
>   	val |= KVM_REG_ARM_DEMUX_ID_CCSIDR;
> -	for (i = 0; i < CSSELR_MAX; i++) {
> +	for (i = 0; i < num_demux_regs(vcpu); i++) {
>   		if (put_user(val | i, uindices))
>   			return -EFAULT;
>   		uindices++;
> @@ -5002,11 +5002,27 @@ static bool copy_reg_to_user(const struct sys_reg_desc *reg, u64 __user **uind)
>   	return true;
>   }
>   
> +static bool kvm_realm_sys_reg_hidden_user(const struct kvm_vcpu *vcpu, u64 reg)
> +{
> +	if (!kvm_is_realm(vcpu->kvm))
> +		return false;
> +
> +	switch (reg) {
> +	case SYS_ID_AA64DFR0_EL1:
> +	case SYS_PMCR_EL0:
> +		return false;
> +	}
> +	return true;
> +}
> +

static inline bool kvm_realm_sys_reg_hidden_user(const struct kvm_vcpu *vcpu, u64 reg)

>   static int walk_one_sys_reg(const struct kvm_vcpu *vcpu,
>   			    const struct sys_reg_desc *rd,
>   			    u64 __user **uind,
>   			    unsigned int *total)
>   {
> +	if (kvm_realm_sys_reg_hidden_user(vcpu, reg_to_encoding(rd)))
> +		return 0;
> +
>   	/*
>   	 * Ignore registers we trap but don't save,
>   	 * and for which no custom user accessor is provided.
> @@ -5044,7 +5060,7 @@ static int walk_sys_regs(struct kvm_vcpu *vcpu, u64 __user *uind)
>   
>   unsigned long kvm_arm_num_sys_reg_descs(struct kvm_vcpu *vcpu)
>   {
> -	return num_demux_regs()
> +	return num_demux_regs(vcpu)
>   		+ walk_sys_regs(vcpu, (u64 __user *)NULL);
>   }
>   
> @@ -5057,7 +5073,7 @@ int kvm_arm_copy_sys_reg_indices(struct kvm_vcpu *vcpu, u64 __user *uindices)
>   		return err;
>   	uindices += err;
>   
> -	return write_demux_regids(uindices);
> +	return write_demux_regids(vcpu, uindices);
>   }
>   
>   #define KVM_ARM_FEATURE_ID_RANGE_INDEX(r)			\

Thanks,
Gavin