On Thu, 23 Sep 2021 12:22:56 +0100,
Will Deacon <will@xxxxxxxxxx> wrote:
>
> After pKVM has been 'finalised' using the __pkvm_prot_finalize hypercall,
> the calling CPU will have a Stage-2 translation enabled to prevent access
> to memory pages owned by EL2.
>
> Although this forms a significant part of the process to deprivilege the
> host kernel, we also need to ensure that the hypercall interface is
> reduced so that the EL2 code cannot, for example, be re-initialised using
> a new set of vectors.
>
> Re-order the hypercalls so that only a suffix remains available after
> finalisation of pKVM.
>
> Cc: Marc Zyngier <maz@xxxxxxxxxx>
> Cc: Quentin Perret <qperret@xxxxxxxxxx>
> Signed-off-by: Will Deacon <will@xxxxxxxxxx>
> ---
> arch/arm64/include/asm/kvm_asm.h | 43 ++++++++++++++++--------------
> arch/arm64/kvm/hyp/nvhe/hyp-main.c | 26 +++++++++++-------
> 2 files changed, 39 insertions(+), 30 deletions(-)
>
> diff --git a/arch/arm64/include/asm/kvm_asm.h b/arch/arm64/include/asm/kvm_asm.h
> index e86045ac43ba..68630fd382c5 100644
> --- a/arch/arm64/include/asm/kvm_asm.h
> +++ b/arch/arm64/include/asm/kvm_asm.h
> @@ -43,27 +43,30 @@
>
> #define KVM_HOST_SMCCC_FUNC(name) KVM_HOST_SMCCC_ID(__KVM_HOST_SMCCC_FUNC_##name)
>
> +/* Hypercalls available only prior to pKVM finalisation */
> #define __KVM_HOST_SMCCC_FUNC___kvm_hyp_init 0
> -#define __KVM_HOST_SMCCC_FUNC___kvm_vcpu_run 1
> -#define __KVM_HOST_SMCCC_FUNC___kvm_flush_vm_context 2
> -#define __KVM_HOST_SMCCC_FUNC___kvm_tlb_flush_vmid_ipa 3
> -#define __KVM_HOST_SMCCC_FUNC___kvm_tlb_flush_vmid 4
> -#define __KVM_HOST_SMCCC_FUNC___kvm_flush_cpu_context 5
> -#define __KVM_HOST_SMCCC_FUNC___kvm_timer_set_cntvoff 6
> -#define __KVM_HOST_SMCCC_FUNC___kvm_enable_ssbs 7
> -#define __KVM_HOST_SMCCC_FUNC___vgic_v3_get_gic_config 8
> -#define __KVM_HOST_SMCCC_FUNC___vgic_v3_read_vmcr 9
> -#define __KVM_HOST_SMCCC_FUNC___vgic_v3_write_vmcr 10
> -#define __KVM_HOST_SMCCC_FUNC___vgic_v3_init_lrs 11
> -#define __KVM_HOST_SMCCC_FUNC___kvm_get_mdcr_el2 12
> -#define __KVM_HOST_SMCCC_FUNC___vgic_v3_save_aprs 13
> -#define __KVM_HOST_SMCCC_FUNC___vgic_v3_restore_aprs 14
> -#define __KVM_HOST_SMCCC_FUNC___pkvm_init 15
> -#define __KVM_HOST_SMCCC_FUNC___pkvm_host_share_hyp 16
> -#define __KVM_HOST_SMCCC_FUNC___pkvm_create_private_mapping 17
> -#define __KVM_HOST_SMCCC_FUNC___pkvm_cpu_set_vector 18
> -#define __KVM_HOST_SMCCC_FUNC___pkvm_prot_finalize 19
> -#define __KVM_HOST_SMCCC_FUNC___kvm_adjust_pc 20
> +#define __KVM_HOST_SMCCC_FUNC___kvm_get_mdcr_el2 1
> +#define __KVM_HOST_SMCCC_FUNC___pkvm_init 2
> +#define __KVM_HOST_SMCCC_FUNC___pkvm_create_private_mapping 3
> +#define __KVM_HOST_SMCCC_FUNC___pkvm_cpu_set_vector 4
> +#define __KVM_HOST_SMCCC_FUNC___kvm_enable_ssbs 5
> +#define __KVM_HOST_SMCCC_FUNC___vgic_v3_init_lrs 6
> +#define __KVM_HOST_SMCCC_FUNC___vgic_v3_get_gic_config 7
> +#define __KVM_HOST_SMCCC_FUNC___pkvm_prot_finalize 8
> +
> +/* Hypercalls available after pKVM finalisation */
> +#define __KVM_HOST_SMCCC_FUNC___pkvm_host_share_hyp 9
> +#define __KVM_HOST_SMCCC_FUNC___kvm_adjust_pc 10
> +#define __KVM_HOST_SMCCC_FUNC___kvm_vcpu_run 11
> +#define __KVM_HOST_SMCCC_FUNC___kvm_flush_vm_context 12
> +#define __KVM_HOST_SMCCC_FUNC___kvm_tlb_flush_vmid_ipa 13
> +#define __KVM_HOST_SMCCC_FUNC___kvm_tlb_flush_vmid 14
> +#define __KVM_HOST_SMCCC_FUNC___kvm_flush_cpu_context 15
> +#define __KVM_HOST_SMCCC_FUNC___kvm_timer_set_cntvoff 16
> +#define __KVM_HOST_SMCCC_FUNC___vgic_v3_read_vmcr 17
> +#define __KVM_HOST_SMCCC_FUNC___vgic_v3_write_vmcr 18
> +#define __KVM_HOST_SMCCC_FUNC___vgic_v3_save_aprs 19
> +#define __KVM_HOST_SMCCC_FUNC___vgic_v3_restore_aprs 20
>
> #ifndef __ASSEMBLY__
>
> diff --git a/arch/arm64/kvm/hyp/nvhe/hyp-main.c b/arch/arm64/kvm/hyp/nvhe/hyp-main.c
> index 2da6aa8da868..4120e34288e1 100644
> --- a/arch/arm64/kvm/hyp/nvhe/hyp-main.c
> +++ b/arch/arm64/kvm/hyp/nvhe/hyp-main.c
> @@ -165,36 +165,42 @@ typedef void (*hcall_t)(struct kvm_cpu_context *);
> #define HANDLE_FUNC(x) [__KVM_HOST_SMCCC_FUNC_##x] = (hcall_t)handle_##x
>
> static const hcall_t host_hcall[] = {
> - HANDLE_FUNC(__kvm_vcpu_run),
> + /* ___kvm_hyp_init */
> + HANDLE_FUNC(__kvm_get_mdcr_el2),
> + HANDLE_FUNC(__pkvm_init),
> + HANDLE_FUNC(__pkvm_create_private_mapping),
> + HANDLE_FUNC(__pkvm_cpu_set_vector),
> + HANDLE_FUNC(__kvm_enable_ssbs),
> + HANDLE_FUNC(__vgic_v3_init_lrs),
> + HANDLE_FUNC(__pkvm_prot_finalize),
> +
> + HANDLE_FUNC(__pkvm_host_share_hyp),
> HANDLE_FUNC(__kvm_adjust_pc),
> + HANDLE_FUNC(__kvm_vcpu_run),
> HANDLE_FUNC(__kvm_flush_vm_context),
> HANDLE_FUNC(__kvm_tlb_flush_vmid_ipa),
> HANDLE_FUNC(__kvm_tlb_flush_vmid),
> HANDLE_FUNC(__kvm_flush_cpu_context),
> HANDLE_FUNC(__kvm_timer_set_cntvoff),
> - HANDLE_FUNC(__kvm_enable_ssbs),
> HANDLE_FUNC(__vgic_v3_get_gic_config),
> HANDLE_FUNC(__vgic_v3_read_vmcr),
> HANDLE_FUNC(__vgic_v3_write_vmcr),
> - HANDLE_FUNC(__vgic_v3_init_lrs),
> - HANDLE_FUNC(__kvm_get_mdcr_el2),
> HANDLE_FUNC(__vgic_v3_save_aprs),
> HANDLE_FUNC(__vgic_v3_restore_aprs),
> - HANDLE_FUNC(__pkvm_init),
> - HANDLE_FUNC(__pkvm_cpu_set_vector),
> - HANDLE_FUNC(__pkvm_host_share_hyp),
> - HANDLE_FUNC(__pkvm_create_private_mapping),
> - HANDLE_FUNC(__pkvm_prot_finalize),
> };
>
> static void handle_host_hcall(struct kvm_cpu_context *host_ctxt)
> {
> DECLARE_REG(unsigned long, id, host_ctxt, 0);
> + unsigned long hcall_min = 0;
> hcall_t hfn;
>
> + if (static_branch_unlikely(&kvm_protected_mode_initialized))
> + hcall_min = __KVM_HOST_SMCCC_FUNC___pkvm_prot_finalize;
> +
> id -= KVM_HOST_SMCCC_ID(0);
>
> - if (unlikely(id >= ARRAY_SIZE(host_hcall)))
> + if (unlikely(id < hcall_min || id >= ARRAY_SIZE(host_hcall)))
So I can still issue a pkvm_prot_finalize after finalisation? Seems
odd. As hcall_min has to be inclusive, you probably want it to be set
to __KVM_HOST_SMCCC_FUNC___pkvm_host_share_hyp once protected.
Thanks,
M.
--
Without deviation from the norm, progress is not possible.
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