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KVM: arm64: Reject stub hypercalls after pKVM has been initialised

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The stub hypercalls provide mechanisms to reset and replace the EL2 code,
so uninstall them once pKVM has been initialised in order to ensure the
integrity of the hypervisor code.

To ensure pKVM initialisation remains functional, split cpu_hyp_reinit()
into two helper functions to separate usage of the stub from usage of
pkvm hypercalls either side of __pkvm_init on the boot CPU.

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/20211008135839.1193-4-will@kernel.org
This commit is contained in:
Will Deacon
2021-10-08 14:58:36 +01:00
committed by Marc Zyngier
parent 8f4566f18d
commit 8579a185ba
2 changed files with 41 additions and 18 deletions
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33
arch/arm64/kvm/arm.c
View File

@@ -1579,25 +1579,33 @@ static void cpu_set_hyp_vector(void)
kvm_call_hyp_nvhe(__pkvm_cpu_set_vector, data->slot);
}
static void cpu_hyp_reinit(void)
static void cpu_hyp_init_context(void)
{
kvm_init_host_cpu_context(&this_cpu_ptr_hyp_sym(kvm_host_data)->host_ctxt);
cpu_hyp_reset();
if (!is_kernel_in_hyp_mode())
cpu_init_hyp_mode();
}
static void cpu_hyp_init_features(void)
{
cpu_set_hyp_vector();
kvm_arm_init_debug();
if (is_kernel_in_hyp_mode())
kvm_timer_init_vhe();
else
cpu_init_hyp_mode();
cpu_set_hyp_vector();
kvm_arm_init_debug();
if (vgic_present)
kvm_vgic_init_cpu_hardware();
}
static void cpu_hyp_reinit(void)
{
cpu_hyp_reset();
cpu_hyp_init_context();
cpu_hyp_init_features();
}
static void _kvm_arch_hardware_enable(void *discard)
{
if (!__this_cpu_read(kvm_arm_hardware_enabled)) {
@@ -1788,10 +1796,17 @@ static int do_pkvm_init(u32 hyp_va_bits)
int ret;
preempt_disable();
hyp_install_host_vector();
cpu_hyp_init_context();
ret = kvm_call_hyp_nvhe(__pkvm_init, hyp_mem_base, hyp_mem_size,
num_possible_cpus(), kern_hyp_va(per_cpu_base),
hyp_va_bits);
cpu_hyp_init_features();
/*
* The stub hypercalls are now disabled, so set our local flag to
* prevent a later re-init attempt in kvm_arch_hardware_enable().
*/
__this_cpu_write(kvm_arm_hardware_enabled, 1);
preempt_enable();
return ret;

26
arch/arm64/kvm/hyp/nvhe/host.S
View File

@@ -110,17 +110,14 @@ SYM_FUNC_START(__hyp_do_panic)
b __host_enter_for_panic
SYM_FUNC_END(__hyp_do_panic)
.macro host_el1_sync_vect
.align 7
.L__vect_start\@:
stp x0, x1, [sp, #-16]!
mrs x0, esr_el2
lsr x0, x0, #ESR_ELx_EC_SHIFT
cmp x0, #ESR_ELx_EC_HVC64
b.ne __host_exit
SYM_FUNC_START(__host_hvc)
ldp x0, x1, [sp] // Don't fixup the stack yet
/* No stub for you, sonny Jim */
alternative_if ARM64_KVM_PROTECTED_MODE
b __host_exit
alternative_else_nop_endif
/* Check for a stub HVC call */
cmp x0, #HVC_STUB_HCALL_NR
b.hs __host_exit
@@ -137,6 +134,17 @@ SYM_FUNC_END(__hyp_do_panic)
ldr x5, =__kvm_handle_stub_hvc
hyp_pa x5, x6
br x5
SYM_FUNC_END(__host_hvc)
.macro host_el1_sync_vect
.align 7
.L__vect_start\@:
stp x0, x1, [sp, #-16]!
mrs x0, esr_el2
lsr x0, x0, #ESR_ELx_EC_SHIFT
cmp x0, #ESR_ELx_EC_HVC64
b.eq __host_hvc
b __host_exit
.L__vect_end\@:
.if ((.L__vect_end\@ - .L__vect_start\@) > 0x80)
.error "host_el1_sync_vect larger than vector entry"