Re: [PATCH v3 05/15] arm64: kvm: Build hyp-entry.S separately for VHE/nVHE

David Brazdil
2020-06-25T11:54:06Z

Hey Marc,

> I'd be happy with the (maybe temporary) magic approach. It helps reasoning
> about things, and makes the transition smoother. Yes, bugs could crop up
> there, but given the static nature of obtaining a symbol's address, I'm
> fairly confident we'll get it right. The same cannot be said about pointers
> though.

Ok, so this is what it would look like:

diff --git a/arch/arm64/include/asm/kvm_asm.h b/arch/arm64/include/asm/kvm_asm.h
index 6a682d66a640..0d1b3b1946f0 100644
--- a/arch/arm64/include/asm/kvm_asm.h
+++ b/arch/arm64/include/asm/kvm_asm.h
@@ -59,13 +59,14 @@
#define DECLARE_KVM_HYP_SYM(sym) \
DECLARE_KVM_VHE_SYM(sym); \
DECLARE_KVM_NVHE_SYM(sym)
+#define CHOOSE_HYP_SYM(sym) (has_vhe() ? sym : kvm_nvhe_sym(sym))

/* Translate a kernel address of @sym into its equivalent linear mapping */
-#define kvm_ksym_ref(sym) \
+#define kvm_ksym_ref(ptr) \
({ \
- void *val = &sym; \
+ void *val = (ptr); \
if (!is_kernel_in_hyp_mode()) \
- val = lm_alias(&sym); \
+ val = lm_alias((ptr)); \
val; \
})
#define kvm_ksym_ref_nvhe(sym) kvm_ksym_ref(kvm_nvhe_sym(sym))
@@ -76,7 +77,14 @@ struct kvm_vcpu;
extern char __kvm_hyp_init[];
extern char __kvm_hyp_init_end[];

-extern char __kvm_hyp_vector[];
+DECLARE_KVM_HYP_SYM(__kvm_hyp_vector);
+#define __kvm_hyp_vector CHOOSE_HYP_SYM(__kvm_hyp_vector)
+
+#ifdef CONFIG_KVM_INDIRECT_VECTORS
+DECLARE_KVM_HYP_SYM(__bp_harden_hyp_vecs);
+#define __bp_harden_hyp_vecs CHOOSE_HYP_SYM(__bp_harden_hyp_vecs)
+extern atomic_t arm64_el2_vector_last_slot;
+#endif

extern void __kvm_flush_vm_context(void);
extern void __kvm_tlb_flush_vmid_ipa(struct kvm *kvm, phys_addr_t ipa);

Everything compiles and boots. Only existing code I had to change was:

diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index 90cb90561446..34b551385153 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -1285,7 +1285,7 @@ static void cpu_init_hyp_mode(void)
* so that we can use adr_l to access per-cpu variables in EL2.
*/
tpidr_el2 = ((unsigned long)this_cpu_ptr(&kvm_host_data) -
- (unsigned long)kvm_ksym_ref(kvm_host_data));
+ (unsigned long)kvm_ksym_ref(&kvm_host_data));

pgd_ptr = kvm_mmu_get_httbr();
hyp_stack_ptr = __this_cpu_read(kvm_arm_hyp_stack_page) + PAGE_SIZE;

WDYT?

Thanks,
-David