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UPSTREAM: KVM: arm64: Disable privileged hypercalls after pKVM finalisation

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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@kernel.org>
Cc: Quentin Perret <qperret@google.com>
Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20211008135839.1193-7-will@kernel.org
(cherry picked from commit 057bed206f)
Bug: 204960018
Signed-off-by: Will Deacon <willdeacon@google.com>
Change-Id: I61e57c7bff456d40866acd01475b2e9ace1e1bd6
This commit is contained in:
Will Deacon
2021-10-08 14:58:39 +01:00
committed by Will Deacon
parent 1612b00146
commit 2f89a13454
2 changed files with 40 additions and 22 deletions
Download Patch File Download Diff File Expand all files Collapse all files

25
arch/arm64/include/asm/kvm_asm.h
View File

@@ -50,27 +50,30 @@
#include <linux/mm.h>
enum __kvm_host_smccc_func {
/* Hypercalls available only prior to pKVM finalisation */
/* __KVM_HOST_SMCCC_FUNC___kvm_hyp_init */
__KVM_HOST_SMCCC_FUNC___kvm_vcpu_run = __KVM_HOST_SMCCC_FUNC___kvm_hyp_init + 1,
__KVM_HOST_SMCCC_FUNC___kvm_get_mdcr_el2 = __KVM_HOST_SMCCC_FUNC___kvm_hyp_init + 1,
__KVM_HOST_SMCCC_FUNC___pkvm_init,
__KVM_HOST_SMCCC_FUNC___pkvm_create_private_mapping,
__KVM_HOST_SMCCC_FUNC___pkvm_cpu_set_vector,
__KVM_HOST_SMCCC_FUNC___kvm_enable_ssbs,
__KVM_HOST_SMCCC_FUNC___vgic_v3_init_lrs,
__KVM_HOST_SMCCC_FUNC___vgic_v3_get_gic_config,
__KVM_HOST_SMCCC_FUNC___pkvm_prot_finalize,
/* Hypercalls available after pKVM finalisation */
__KVM_HOST_SMCCC_FUNC___pkvm_host_share_hyp,
__KVM_HOST_SMCCC_FUNC___kvm_adjust_pc,
__KVM_HOST_SMCCC_FUNC___kvm_vcpu_run,
__KVM_HOST_SMCCC_FUNC___kvm_flush_vm_context,
__KVM_HOST_SMCCC_FUNC___kvm_tlb_flush_vmid_ipa,
__KVM_HOST_SMCCC_FUNC___kvm_tlb_flush_vmid,
__KVM_HOST_SMCCC_FUNC___kvm_flush_cpu_context,
__KVM_HOST_SMCCC_FUNC___kvm_timer_set_cntvoff,
__KVM_HOST_SMCCC_FUNC___kvm_enable_ssbs,
__KVM_HOST_SMCCC_FUNC___vgic_v3_get_gic_config,
__KVM_HOST_SMCCC_FUNC___vgic_v3_read_vmcr,
__KVM_HOST_SMCCC_FUNC___vgic_v3_write_vmcr,
__KVM_HOST_SMCCC_FUNC___vgic_v3_init_lrs,
__KVM_HOST_SMCCC_FUNC___kvm_get_mdcr_el2,
__KVM_HOST_SMCCC_FUNC___vgic_v3_save_aprs,
__KVM_HOST_SMCCC_FUNC___vgic_v3_restore_aprs,
__KVM_HOST_SMCCC_FUNC___pkvm_init,
__KVM_HOST_SMCCC_FUNC___pkvm_host_share_hyp,
__KVM_HOST_SMCCC_FUNC___pkvm_create_private_mapping,
__KVM_HOST_SMCCC_FUNC___pkvm_cpu_set_vector,
__KVM_HOST_SMCCC_FUNC___pkvm_prot_finalize,
__KVM_HOST_SMCCC_FUNC___kvm_adjust_pc,
};
#define DECLARE_KVM_VHE_SYM(sym) extern char sym[]

37
arch/arm64/kvm/hyp/nvhe/hyp-main.c
View File

@@ -165,36 +165,51 @@ 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(__vgic_v3_get_gic_config),
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 pKVM has been initialised then reject any calls to the
* early "privileged" hypercalls. Note that we cannot reject
* calls to __pkvm_prot_finalize for two reasons: (1) The static
* key used to determine initialisation must be toggled prior to
* finalisation and (2) finalisation is performed on a per-CPU
* basis. This is all fine, however, since __pkvm_prot_finalize
* returns -EPERM after the first call for a given CPU.
*/
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)))
goto inval;
hfn = host_hcall[id];