On Thu, Sep 23, 2021 at 01:56:21PM +0100, Marc Zyngier wrote: > On Thu, 23 Sep 2021 12:22:56 +0100, > Will Deacon <[email protected]> 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 <[email protected]> > > Cc: Quentin Perret <[email protected]> > > Signed-off-by: Will Deacon <[email protected]> > > --- > > 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.
Yeah, I ended up addresing that one in the previous patch. The problem is that we need to allow pkvm_prot_finalize to be called on each CPU, so I think we'd end up having an extra "really finalize damnit!" call to be issued _once_ after each CPU is done with the finalisation if we want to lock it down. The approach I took instead is to make pkvm_prot_finalize return -EBUSY if it's called on a CPU where it's already been called. Will _______________________________________________ kvmarm mailing list [email protected] https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
