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KVM: arm64: Unmap 'kvm_arm_hyp_percpu_base' from the host

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When pKVM is enabled, the hypervisor at EL2 does not trust the host at
EL1 and must therefore prevent it from having unrestricted access to
internal hypervisor state.

The 'kvm_arm_hyp_percpu_base' array holds the offsets for hypervisor
per-cpu allocations, so move this this into the nVHE code where it
cannot be modified by the untrusted host at EL1.

Tested-by: Vincent Donnefort <vdonnefort@google.com>
Signed-off-by: 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/20221110190259.26861-22-will@kernel.org
This commit is contained in:
Quentin Perret 2022-11-10 19:02:54 +00:00 committed by Marc Zyngier
parent f41dff4efb
commit fe41a7f8c0
4 changed files with 8 additions and 10 deletions
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4
arch/arm64/include/asm/kvm_asm.h
View file

@ -109,7 +109,7 @@ enum __kvm_host_smccc_func {
#define per_cpu_ptr_nvhe_sym(sym, cpu) \
({ \
unsigned long base, off; \
base = kvm_arm_hyp_percpu_base[cpu]; \
base = kvm_nvhe_sym(kvm_arm_hyp_percpu_base)[cpu]; \
off = (unsigned long)&CHOOSE_NVHE_SYM(sym) - \
(unsigned long)&CHOOSE_NVHE_SYM(__per_cpu_start); \
base ? (typeof(CHOOSE_NVHE_SYM(sym))*)(base + off) : NULL; \
@ -214,7 +214,7 @@ DECLARE_KVM_HYP_SYM(__kvm_hyp_vector);
#define __kvm_hyp_init CHOOSE_NVHE_SYM(__kvm_hyp_init)
#define __kvm_hyp_vector CHOOSE_HYP_SYM(__kvm_hyp_vector)
extern unsigned long kvm_arm_hyp_percpu_base[NR_CPUS];
extern unsigned long kvm_nvhe_sym(kvm_arm_hyp_percpu_base)[];
DECLARE_KVM_NVHE_SYM(__per_cpu_start);
DECLARE_KVM_NVHE_SYM(__per_cpu_end);

3
arch/arm64/kernel/image-vars.h
View file

@ -89,9 +89,6 @@ KVM_NVHE_ALIAS(gic_nonsecure_priorities);
KVM_NVHE_ALIAS(__start___kvm_ex_table);
KVM_NVHE_ALIAS(__stop___kvm_ex_table);
/* Array containing bases of nVHE per-CPU memory regions. */
KVM_NVHE_ALIAS(kvm_arm_hyp_percpu_base);
/* PMU available static key */
#ifdef CONFIG_HW_PERF_EVENTS
KVM_NVHE_ALIAS(kvm_arm_pmu_available);

9
arch/arm64/kvm/arm.c
View file

@ -51,7 +51,6 @@ DEFINE_STATIC_KEY_FALSE(kvm_protected_mode_initialized);
DECLARE_KVM_HYP_PER_CPU(unsigned long, kvm_hyp_vector);
DEFINE_PER_CPU(unsigned long, kvm_arm_hyp_stack_page);
unsigned long kvm_arm_hyp_percpu_base[NR_CPUS];
DECLARE_KVM_NVHE_PER_CPU(struct kvm_nvhe_init_params, kvm_init_params);
static bool vgic_present;
@ -1857,13 +1856,13 @@ static void teardown_hyp_mode(void)
free_hyp_pgds();
for_each_possible_cpu(cpu) {
free_page(per_cpu(kvm_arm_hyp_stack_page, cpu));
free_pages(kvm_arm_hyp_percpu_base[cpu], nvhe_percpu_order());
free_pages(kvm_nvhe_sym(kvm_arm_hyp_percpu_base)[cpu], nvhe_percpu_order());
}
}
static int do_pkvm_init(u32 hyp_va_bits)
{
void *per_cpu_base = kvm_ksym_ref(kvm_arm_hyp_percpu_base);
void *per_cpu_base = kvm_ksym_ref(kvm_nvhe_sym(kvm_arm_hyp_percpu_base));
int ret;
preempt_disable();
@ -1967,7 +1966,7 @@ static int init_hyp_mode(void)
page_addr = page_address(page);
memcpy(page_addr, CHOOSE_NVHE_SYM(__per_cpu_start), nvhe_percpu_size());
kvm_arm_hyp_percpu_base[cpu] = (unsigned long)page_addr;
kvm_nvhe_sym(kvm_arm_hyp_percpu_base)[cpu] = (unsigned long)page_addr;
}
/*
@ -2060,7 +2059,7 @@ static int init_hyp_mode(void)
}
for_each_possible_cpu(cpu) {
char *percpu_begin = (char *)kvm_arm_hyp_percpu_base[cpu];
char *percpu_begin = (char *)kvm_nvhe_sym(kvm_arm_hyp_percpu_base)[cpu];
char *percpu_end = percpu_begin + nvhe_percpu_size();
/* Map Hyp percpu pages */

2
arch/arm64/kvm/hyp/nvhe/hyp-smp.c
View file

@ -23,6 +23,8 @@ u64 cpu_logical_map(unsigned int cpu)
return hyp_cpu_logical_map[cpu];
}
unsigned long __ro_after_init kvm_arm_hyp_percpu_base[NR_CPUS];
unsigned long __hyp_per_cpu_offset(unsigned int cpu)
{
unsigned long *cpu_base_array;