Re: [RFC PATCH 1/8] KVM: arm64: Factor out firmware register handling from psci.c

From: Oliver Upton
Date: Wed Nov 03 2021 - 17:43:40 EST

Hi Raghu,

On Tue, Nov 02, 2021 at 12:21:56AM +0000, Raghavendra Rao Ananta wrote:
> Common hypercall firmware register handing is currently employed
> by psci.c. Since the upcoming patches add more of these registers,
> it's better to move the generic handling to hypercall.c for a
> cleaner presentation.
>
> While we are at it, collect all the firmware registers under
> fw_reg_ids[] to help implement kvm_arm_get_fw_num_regs() and
> kvm_arm_copy_fw_reg_indices() in a generic way.
>
> No functional change intended.
>
> Signed-off-by: Raghavendra Rao Ananta <rananta@xxxxxxxxxx>
> ---
> arch/arm64/kvm/guest.c | 2 +-
> arch/arm64/kvm/hypercalls.c | 151 +++++++++++++++++++++++++++++++
> arch/arm64/kvm/psci.c | 167 +++--------------------------------
> include/kvm/arm_hypercalls.h | 7 ++
> include/kvm/arm_psci.h | 8 +-
> 5 files changed, 172 insertions(+), 163 deletions(-)
>
> diff --git a/arch/arm64/kvm/guest.c b/arch/arm64/kvm/guest.c
> index 5ce26bedf23c..625f97f7b304 100644
> --- a/arch/arm64/kvm/guest.c
> +++ b/arch/arm64/kvm/guest.c
> @@ -18,7 +18,7 @@
> #include <linux/string.h>
> #include <linux/vmalloc.h>
> #include <linux/fs.h>
> -#include <kvm/arm_psci.h>
> +#include <kvm/arm_hypercalls.h>
> #include <asm/cputype.h>
> #include <linux/uaccess.h>
> #include <asm/fpsimd.h>
> diff --git a/arch/arm64/kvm/hypercalls.c b/arch/arm64/kvm/hypercalls.c
> index 30da78f72b3b..d030939c5929 100644
> --- a/arch/arm64/kvm/hypercalls.c
> +++ b/arch/arm64/kvm/hypercalls.c
> @@ -146,3 +146,154 @@ int kvm_hvc_call_handler(struct kvm_vcpu *vcpu)
> smccc_set_retval(vcpu, val[0], val[1], val[2], val[3]);
> return 1;
> }
> +
> +static const u64 fw_reg_ids[] = {
> + KVM_REG_ARM_PSCI_VERSION,
> + KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_1,
> + KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2,
> +};
> +
> +int kvm_arm_get_fw_num_regs(struct kvm_vcpu *vcpu)
> +{
> + return ARRAY_SIZE(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(fw_reg_ids); i++) {
> + if (put_user(fw_reg_ids[i], uindices))
> + return -EFAULT;
> + }
> +
> + return 0;
> +}

It would appear that this patch is separating out the hypercall services
to each handle their own FW regs. At the same time, this is
consolidating the register enumeration into a single place.

It would be nice to keep the scoping consistent with your accessors
below, or simply just handle all regs in hypercalls.c. Abstracting
per-service might result in a lot of boilerplate, though.

> +#define KVM_REG_FEATURE_LEVEL_WIDTH 4
> +#define KVM_REG_FEATURE_LEVEL_MASK (BIT(KVM_REG_FEATURE_LEVEL_WIDTH) - 1)
> +
> +/*
> + * Convert the workaround level into an easy-to-compare number, where higher
> + * values mean better protection.
> + */
> +static int get_kernel_wa_level(u64 regid)
> +{
> + switch (regid) {
> + case KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_1:
> + switch (arm64_get_spectre_v2_state()) {
> + case SPECTRE_VULNERABLE:
> + return KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_1_NOT_AVAIL;
> + case SPECTRE_MITIGATED:
> + return KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_1_AVAIL;
> + case SPECTRE_UNAFFECTED:
> + return KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_1_NOT_REQUIRED;
> + }
> + return KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_1_NOT_AVAIL;
> + case KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2:
> + switch (arm64_get_spectre_v4_state()) {
> + case SPECTRE_MITIGATED:
> + /*
> + * As for the hypercall discovery, we pretend we
> + * don't have any FW mitigation if SSBS is there at
> + * all times.
> + */
> + if (cpus_have_final_cap(ARM64_SSBS))
> + return KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_NOT_AVAIL;
> + fallthrough;
> + case SPECTRE_UNAFFECTED:
> + return KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_NOT_REQUIRED;
> + case SPECTRE_VULNERABLE:
> + return KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_NOT_AVAIL;
> + }
> + }
> +
> + return -EINVAL;
> +}
> +
> +int kvm_arm_get_fw_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
> +{
> + void __user *uaddr = (void __user *)(long)reg->addr;
> + u64 val;
> +
> + switch (reg->id) {
> + case KVM_REG_ARM_PSCI_VERSION:
> + val = kvm_psci_version(vcpu, vcpu->kvm);

Should this become kvm_arm_get_fw_reg() to consistently genericize the
PSCI FW register accessors?

> + break;
> + case KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_1:
> + case KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2:
> + val = get_kernel_wa_level(reg->id) & KVM_REG_FEATURE_LEVEL_MASK;
> + break;
> + default:
> + return -ENOENT;
> + }
> +
> + if (copy_to_user(uaddr, &val, KVM_REG_SIZE(reg->id)))
> + return -EFAULT;
> +
> + return 0;
> +}
> +
> +int kvm_arm_set_fw_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
> +{
> + void __user *uaddr = (void __user *)(long)reg->addr;
> + u64 val;
> + int wa_level;
> +
> + if (copy_from_user(&val, uaddr, KVM_REG_SIZE(reg->id)))
> + return -EFAULT;
> +
> + switch (reg->id) {
> + case KVM_REG_ARM_PSCI_VERSION:
> + return kvm_arm_set_psci_fw_reg(vcpu, val);
> +
> + case KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_1:
> + if (val & ~KVM_REG_FEATURE_LEVEL_MASK)
> + return -EINVAL;
> +
> + if (get_kernel_wa_level(reg->id) < val)
> + return -EINVAL;
> +
> + return 0;
> +
> + case KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2:
> + if (val & ~(KVM_REG_FEATURE_LEVEL_MASK |
> + KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_ENABLED))
> + return -EINVAL;
> +
> + /* The enabled bit must not be set unless the level is AVAIL. */
> + if ((val & KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_ENABLED) &&
> + (val & KVM_REG_FEATURE_LEVEL_MASK) != KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_AVAIL)
> + return -EINVAL;
> +
> + /*
> + * Map all the possible incoming states to the only two we
> + * really want to deal with.
> + */
> + switch (val & KVM_REG_FEATURE_LEVEL_MASK) {
> + case KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_NOT_AVAIL:
> + case KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_UNKNOWN:
> + wa_level = KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_NOT_AVAIL;
> + break;
> + case KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_AVAIL:
> + case KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_NOT_REQUIRED:
> + wa_level = KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_NOT_REQUIRED;
> + break;
> + default:
> + return -EINVAL;
> + }
> +
> + /*
> + * We can deal with NOT_AVAIL on NOT_REQUIRED, but not the
> + * other way around.
> + */
> + if (get_kernel_wa_level(reg->id) < wa_level)
> + return -EINVAL;
> +
> + return 0;
> + default:
> + return -ENOENT;
> + }
> +
> + return -EINVAL;
> +}
> diff --git a/arch/arm64/kvm/psci.c b/arch/arm64/kvm/psci.c
> index 74c47d420253..b9bcbc919b19 100644
> --- a/arch/arm64/kvm/psci.c
> +++ b/arch/arm64/kvm/psci.c
> @@ -404,168 +404,25 @@ int kvm_psci_call(struct kvm_vcpu *vcpu)
> };
> }
>
> -int kvm_arm_get_fw_num_regs(struct kvm_vcpu *vcpu)
> +int kvm_arm_set_psci_fw_reg(struct kvm_vcpu *vcpu, u64 val)
> {
> - return 3; /* PSCI version and two workaround registers */
> -}
> -
> -int kvm_arm_copy_fw_reg_indices(struct kvm_vcpu *vcpu, u64 __user *uindices)
> -{
> - if (put_user(KVM_REG_ARM_PSCI_VERSION, uindices++))
> - return -EFAULT;
> -
> - if (put_user(KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_1, uindices++))
> - return -EFAULT;
> -
> - if (put_user(KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2, uindices++))
> - return -EFAULT;
> -
> - return 0;
> -}
> + bool wants_02;
>
> -#define KVM_REG_FEATURE_LEVEL_WIDTH 4
> -#define KVM_REG_FEATURE_LEVEL_MASK (BIT(KVM_REG_FEATURE_LEVEL_WIDTH) - 1)
> -
> -/*
> - * Convert the workaround level into an easy-to-compare number, where higher
> - * values mean better protection.
> - */
> -static int get_kernel_wa_level(u64 regid)
> -{
> - switch (regid) {
> - case KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_1:
> - switch (arm64_get_spectre_v2_state()) {
> - case SPECTRE_VULNERABLE:
> - return KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_1_NOT_AVAIL;
> - case SPECTRE_MITIGATED:
> - return KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_1_AVAIL;
> - case SPECTRE_UNAFFECTED:
> - return KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_1_NOT_REQUIRED;
> - }
> - return KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_1_NOT_AVAIL;
> - case KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2:
> - switch (arm64_get_spectre_v4_state()) {
> - case SPECTRE_MITIGATED:
> - /*
> - * As for the hypercall discovery, we pretend we
> - * don't have any FW mitigation if SSBS is there at
> - * all times.
> - */
> - if (cpus_have_final_cap(ARM64_SSBS))
> - return KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_NOT_AVAIL;
> - fallthrough;
> - case SPECTRE_UNAFFECTED:
> - return KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_NOT_REQUIRED;
> - case SPECTRE_VULNERABLE:
> - return KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_NOT_AVAIL;
> - }
> - }
> + wants_02 = test_bit(KVM_ARM_VCPU_PSCI_0_2, vcpu->arch.features);
>
> - return -EINVAL;
> -}
> -
> -int kvm_arm_get_fw_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
> -{
> - void __user *uaddr = (void __user *)(long)reg->addr;
> - u64 val;
> -
> - switch (reg->id) {
> - case KVM_REG_ARM_PSCI_VERSION:
> - val = kvm_psci_version(vcpu, vcpu->kvm);
> - break;
> - case KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_1:
> - case KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2:
> - val = get_kernel_wa_level(reg->id) & KVM_REG_FEATURE_LEVEL_MASK;
> - break;
> - default:
> - return -ENOENT;
> - }
> -
> - if (copy_to_user(uaddr, &val, KVM_REG_SIZE(reg->id)))
> - return -EFAULT;
> -
> - return 0;
> -}
> -
> -int kvm_arm_set_fw_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
> -{
> - void __user *uaddr = (void __user *)(long)reg->addr;
> - u64 val;
> - int wa_level;
> -
> - if (copy_from_user(&val, uaddr, KVM_REG_SIZE(reg->id)))
> - return -EFAULT;
> -
> - switch (reg->id) {
> - case KVM_REG_ARM_PSCI_VERSION:
> - {
> - bool wants_02;
> -
> - wants_02 = test_bit(KVM_ARM_VCPU_PSCI_0_2, vcpu->arch.features);
> -
> - switch (val) {
> - case KVM_ARM_PSCI_0_1:
> - if (wants_02)
> - return -EINVAL;
> - vcpu->kvm->arch.psci_version = val;
> - return 0;
> - case KVM_ARM_PSCI_0_2:
> - case KVM_ARM_PSCI_1_0:
> - if (!wants_02)
> - return -EINVAL;
> - vcpu->kvm->arch.psci_version = val;
> - return 0;
> - }
> - break;
> - }
> -
> - case KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_1:
> - if (val & ~KVM_REG_FEATURE_LEVEL_MASK)
> - return -EINVAL;
> -
> - if (get_kernel_wa_level(reg->id) < val)
> + switch (val) {
> + case KVM_ARM_PSCI_0_1:
> + if (wants_02)
> return -EINVAL;
> -
> + vcpu->kvm->arch.psci_version = val;
> return 0;
> -
> - case KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2:
> - if (val & ~(KVM_REG_FEATURE_LEVEL_MASK |
> - KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_ENABLED))
> - return -EINVAL;
> -
> - /* The enabled bit must not be set unless the level is AVAIL. */
> - if ((val & KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_ENABLED) &&
> - (val & KVM_REG_FEATURE_LEVEL_MASK) != KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_AVAIL)
> - return -EINVAL;
> -
> - /*
> - * Map all the possible incoming states to the only two we
> - * really want to deal with.
> - */
> - switch (val & KVM_REG_FEATURE_LEVEL_MASK) {
> - case KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_NOT_AVAIL:
> - case KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_UNKNOWN:
> - wa_level = KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_NOT_AVAIL;
> - break;
> - case KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_AVAIL:
> - case KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_NOT_REQUIRED:
> - wa_level = KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_NOT_REQUIRED;
> - break;
> - default:
> - return -EINVAL;
> - }
> -
> - /*
> - * We can deal with NOT_AVAIL on NOT_REQUIRED, but not the
> - * other way around.
> - */
> - if (get_kernel_wa_level(reg->id) < wa_level)
> + case KVM_ARM_PSCI_0_2:
> + case KVM_ARM_PSCI_1_0:
> + if (!wants_02)
> return -EINVAL;
> -
> + vcpu->kvm->arch.psci_version = val;
> return 0;
> default:
> - return -ENOENT;
> + return -EINVAL;
> }
> -
> - return -EINVAL;
> }
> diff --git a/include/kvm/arm_hypercalls.h b/include/kvm/arm_hypercalls.h
> index 0e2509d27910..5d38628a8d04 100644
> --- a/include/kvm/arm_hypercalls.h
> +++ b/include/kvm/arm_hypercalls.h
> @@ -40,4 +40,11 @@ static inline void smccc_set_retval(struct kvm_vcpu *vcpu,
> vcpu_set_reg(vcpu, 3, a3);
> }
>
> +struct kvm_one_reg;
> +
> +int kvm_arm_get_fw_num_regs(struct kvm_vcpu *vcpu);
> +int kvm_arm_copy_fw_reg_indices(struct kvm_vcpu *vcpu, u64 __user *uindices);
> +int kvm_arm_get_fw_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg);
> +int kvm_arm_set_fw_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg);
> +
> #endif
> diff --git a/include/kvm/arm_psci.h b/include/kvm/arm_psci.h
> index 5b58bd2fe088..eddbd7d805e9 100644
> --- a/include/kvm/arm_psci.h
> +++ b/include/kvm/arm_psci.h
> @@ -41,12 +41,6 @@ static inline int kvm_psci_version(struct kvm_vcpu *vcpu, struct kvm *kvm)
>
>
> int kvm_psci_call(struct kvm_vcpu *vcpu);
> -
> -struct kvm_one_reg;
> -
> -int kvm_arm_get_fw_num_regs(struct kvm_vcpu *vcpu);
> -int kvm_arm_copy_fw_reg_indices(struct kvm_vcpu *vcpu, u64 __user *uindices);
> -int kvm_arm_get_fw_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg);
> -int kvm_arm_set_fw_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg);
> +int kvm_arm_set_psci_fw_reg(struct kvm_vcpu *vcpu, u64 val);
>
> #endif /* __KVM_ARM_PSCI_H__ */
> --
> 2.33.1.1089.g2158813163f-goog
>