[PATCH v4 07/13] KVM: arm64: Add vendor hypervisor firmware register
Oliver Upton
oupton at google.com
Mon Mar 14 12:59:28 PDT 2022
On Thu, Feb 24, 2022 at 05:25:53PM +0000, Raghavendra Rao Ananta wrote:
> Introduce the firmware register to hold the vendor specific
> hypervisor service calls (owner value 6) as a bitmap. The
> bitmap represents the features that'll be enabled for the
> guest, as configured by the user-space. Currently, this
> includes support only for Precision Time Protocol (PTP),
> represented by bit-0.
>
> The register is also added to the kvm_arm_vm_scope_fw_regs[]
> list as it maintains its state per-VM.
>
> Signed-off-by: Raghavendra Rao Ananta <rananta at google.com>
> ---
> arch/arm64/include/asm/kvm_host.h | 2 ++
> arch/arm64/include/uapi/asm/kvm.h | 4 ++++
> arch/arm64/kvm/guest.c | 1 +
> arch/arm64/kvm/hypercalls.c | 22 +++++++++++++++++++++-
> include/kvm/arm_hypercalls.h | 3 +++
> 5 files changed, 31 insertions(+), 1 deletion(-)
>
> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
> index 318148b69279..d999456c4604 100644
> --- a/arch/arm64/include/asm/kvm_host.h
> +++ b/arch/arm64/include/asm/kvm_host.h
> @@ -106,10 +106,12 @@ struct kvm_arch_memory_slot {
> *
> * @hvc_std_bmap: Bitmap of standard secure service calls
> * @hvc_std_hyp_bmap: Bitmap of standard hypervisor service calls
> + * @hvc_vendor_hyp_bmap: Bitmap of vendor specific hypervisor service calls
> */
> struct kvm_hvc_desc {
> u64 hvc_std_bmap;
> u64 hvc_std_hyp_bmap;
> + u64 hvc_vendor_hyp_bmap;
> };
>
> struct kvm_arch {
> diff --git a/arch/arm64/include/uapi/asm/kvm.h b/arch/arm64/include/uapi/asm/kvm.h
> index 9a2caead7359..ed470bde13d8 100644
> --- a/arch/arm64/include/uapi/asm/kvm.h
> +++ b/arch/arm64/include/uapi/asm/kvm.h
> @@ -299,6 +299,10 @@ struct kvm_arm_copy_mte_tags {
> #define KVM_REG_ARM_STD_HYP_BIT_PV_TIME BIT(0)
> #define KVM_REG_ARM_STD_HYP_BMAP_BIT_MAX 0 /* Last valid bit */
>
> +#define KVM_REG_ARM_VENDOR_HYP_BMAP KVM_REG_ARM_FW_BMAP_REG(2)
> +#define KVM_REG_ARM_VENDOR_HYP_BIT_PTP BIT(0)
> +#define KVM_REG_ARM_VENDOR_HYP_BMAP_BIT_MAX 0 /* Last valid bit */
> +
> /* SVE registers */
> #define KVM_REG_ARM64_SVE (0x15 << KVM_REG_ARM_COPROC_SHIFT)
>
> diff --git a/arch/arm64/kvm/guest.c b/arch/arm64/kvm/guest.c
> index c42426d6137e..fc3656f91aed 100644
> --- a/arch/arm64/kvm/guest.c
> +++ b/arch/arm64/kvm/guest.c
> @@ -67,6 +67,7 @@ static const u64 kvm_arm_vm_scope_fw_regs[] = {
> KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2,
> KVM_REG_ARM_STD_BMAP,
> KVM_REG_ARM_STD_HYP_BMAP,
> + KVM_REG_ARM_VENDOR_HYP_BMAP,
> };
>
> /**
> diff --git a/arch/arm64/kvm/hypercalls.c b/arch/arm64/kvm/hypercalls.c
> index ebc0cc26cf2e..5c5098c8f1f9 100644
> --- a/arch/arm64/kvm/hypercalls.c
> +++ b/arch/arm64/kvm/hypercalls.c
> @@ -79,6 +79,9 @@ static bool kvm_hvc_call_supported(struct kvm_vcpu *vcpu, u32 func_id)
> case ARM_SMCCC_HV_PV_TIME_ST:
> return kvm_arm_fw_reg_feat_enabled(hvc_desc->hvc_std_hyp_bmap,
> KVM_REG_ARM_STD_HYP_BIT_PV_TIME);
> + case ARM_SMCCC_VENDOR_HYP_KVM_PTP_FUNC_ID:
> + return kvm_arm_fw_reg_feat_enabled(hvc_desc->hvc_vendor_hyp_bmap,
> + KVM_REG_ARM_VENDOR_HYP_BIT_PTP);
> default:
> /* By default, allow the services that aren't listed here */
> return true;
> @@ -162,7 +165,14 @@ int kvm_hvc_call_handler(struct kvm_vcpu *vcpu)
> break;
> case ARM_SMCCC_VENDOR_HYP_KVM_FEATURES_FUNC_ID:
> val[0] = BIT(ARM_SMCCC_KVM_FUNC_FEATURES);
> - val[0] |= BIT(ARM_SMCCC_KVM_FUNC_PTP);
> +
> + /*
> + * The feature bits exposed to user-space doesn't include
> + * ARM_SMCCC_KVM_FUNC_FEATURES. However, we expose this to
> + * the guest as bit-0. Hence, left-shift the user-space
> + * exposed bitmap by 1 to accommodate this.
> + */
> + val[0] |= hvc_desc->hvc_vendor_hyp_bmap << 1;
Having an off-by-one difference between the userspace and guest
representations of this bitmap seems like it could be a source of bugs
in the future. Its also impossible for the guest to completely hide the
vendor range if it so chooses.
Why not tie ARM_SMCCC_VENDOR_HYP_CALL_UID_FUNC_ID and
ARM_SMCCC_VENDOR_HYP_KVM_FEATURES_FUNC_ID to BIT(0)? PTP would then
become BIT(1).
> break;
> case ARM_SMCCC_VENDOR_HYP_KVM_PTP_FUNC_ID:
> kvm_ptp_get_time(vcpu, val);
> @@ -188,6 +198,7 @@ static const u64 kvm_arm_fw_reg_ids[] = {
> KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2,
> KVM_REG_ARM_STD_BMAP,
> KVM_REG_ARM_STD_HYP_BMAP,
> + KVM_REG_ARM_VENDOR_HYP_BMAP,
> };
>
> void kvm_arm_init_hypercalls(struct kvm *kvm)
> @@ -196,6 +207,7 @@ void kvm_arm_init_hypercalls(struct kvm *kvm)
>
> hvc_desc->hvc_std_bmap = ARM_SMCCC_STD_FEATURES;
> hvc_desc->hvc_std_hyp_bmap = ARM_SMCCC_STD_HYP_FEATURES;
> + hvc_desc->hvc_vendor_hyp_bmap = ARM_SMCCC_VENDOR_HYP_FEATURES;
> }
>
> int kvm_arm_get_fw_num_regs(struct kvm_vcpu *vcpu)
> @@ -285,6 +297,9 @@ int kvm_arm_get_fw_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
> case KVM_REG_ARM_STD_HYP_BMAP:
> val = READ_ONCE(hvc_desc->hvc_std_hyp_bmap);
> break;
> + case KVM_REG_ARM_VENDOR_HYP_BMAP:
> + val = READ_ONCE(hvc_desc->hvc_vendor_hyp_bmap);
> + break;
> default:
> return -ENOENT;
> }
> @@ -311,6 +326,10 @@ static int kvm_arm_set_fw_reg_bmap(struct kvm_vcpu *vcpu, u64 reg_id, u64 val)
> fw_reg_bmap = &hvc_desc->hvc_std_hyp_bmap;
> fw_reg_features = ARM_SMCCC_STD_HYP_FEATURES;
> break;
> + case KVM_REG_ARM_VENDOR_HYP_BMAP:
> + fw_reg_bmap = &hvc_desc->hvc_vendor_hyp_bmap;
> + fw_reg_features = ARM_SMCCC_VENDOR_HYP_FEATURES;
> + break;
> default:
> return -ENOENT;
> }
> @@ -416,6 +435,7 @@ int kvm_arm_set_fw_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
> return 0;
> case KVM_REG_ARM_STD_BMAP:
> case KVM_REG_ARM_STD_HYP_BMAP:
> + case KVM_REG_ARM_VENDOR_HYP_BMAP:
> return kvm_arm_set_fw_reg_bmap(vcpu, reg_id, val);
> default:
> return -ENOENT;
> diff --git a/include/kvm/arm_hypercalls.h b/include/kvm/arm_hypercalls.h
> index a1cb6e839c74..91be758ca58e 100644
> --- a/include/kvm/arm_hypercalls.h
> +++ b/include/kvm/arm_hypercalls.h
> @@ -12,6 +12,9 @@
> #define ARM_SMCCC_STD_HYP_FEATURES \
> GENMASK_ULL(KVM_REG_ARM_STD_HYP_BMAP_BIT_MAX, 0)
>
> +#define ARM_SMCCC_VENDOR_HYP_FEATURES \
> + GENMASK_ULL(KVM_REG_ARM_VENDOR_HYP_BMAP_BIT_MAX, 0)
> +
> int kvm_hvc_call_handler(struct kvm_vcpu *vcpu);
>
> static inline u32 smccc_get_function(struct kvm_vcpu *vcpu)
> --
> 2.35.1.473.g83b2b277ed-goog
>
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