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

Marc Zyngier
2020-06-18T17:17:20Z

Hi David,

On 2020-06-18 13:25, David Brazdil wrote:
> This patch is part of a series which builds KVM's non-VHE hyp code
> separately
> from VHE and the rest of the kernel.

The above comment doesn't really belong here, and us only fit for the
cover letter.

>
> hyp-entry.S contains implementation of KVM hyp vectors. This code is
> mostly
> shared between VHE/nVHE, therefore compile it under both VHE and nVHE
> build
> rules. nVHE-specific host HVC handler is hidden behind
> __KVM_NVHE_HYPERVISOR__.
>
> Adjust code which selects which KVM hyp vecs to install to choose the
> correct
> VHE/nVHE symbol.
>
> Signed-off-by: David Brazdil <dbrazdil@google.com>
> ---
> arch/arm64/include/asm/kvm_asm.h | 7 ++++++-
> arch/arm64/include/asm/kvm_mmu.h | 16 ++++++++++------
> arch/arm64/include/asm/mmu.h | 7 -------
> arch/arm64/kernel/cpu_errata.c | 4 +++-
> arch/arm64/kernel/image-vars.h | 12 ++++++++++++
> arch/arm64/kvm/hyp/hyp-entry.S | 2 ++
> arch/arm64/kvm/hyp/nvhe/Makefile | 2 +-
> arch/arm64/kvm/va_layout.c | 2 +-
> 8 files changed, 35 insertions(+), 17 deletions(-)
>
> diff --git a/arch/arm64/include/asm/kvm_asm.h
> b/arch/arm64/include/asm/kvm_asm.h
> index 6a682d66a640..2baa69324cc9 100644
> --- a/arch/arm64/include/asm/kvm_asm.h
> +++ b/arch/arm64/include/asm/kvm_asm.h
> @@ -76,7 +76,12 @@ 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);
> +
> +#ifdef CONFIG_KVM_INDIRECT_VECTORS
> +DECLARE_KVM_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);
> diff --git a/arch/arm64/include/asm/kvm_mmu.h
> b/arch/arm64/include/asm/kvm_mmu.h
> index b12bfc1f051a..5bfc7ee61997 100644
> --- a/arch/arm64/include/asm/kvm_mmu.h
> +++ b/arch/arm64/include/asm/kvm_mmu.h
> @@ -461,11 +461,15 @@ extern int __kvm_harden_el2_vector_slot;
> static inline void *kvm_get_hyp_vector(void)
> {
> struct bp_hardening_data *data = arm64_get_bp_hardening_data();
> - void *vect = kern_hyp_va(kvm_ksym_ref(__kvm_hyp_vector));
> int slot = -1;
> + void *vect = kern_hyp_va(has_vhe()
> + ? kvm_ksym_ref(__kvm_hyp_vector)
> + : kvm_ksym_ref_nvhe(__kvm_hyp_vector));

If you are introducing has_vhe() at this stage, then you might as well
not apply kernel_hyp_va() to the address. This also make the declaration
block look a bit ugly (yes, I'm a bit of a maniac). I'd rather see
something like:

diff --git a/arch/arm64/include/asm/kvm_mmu.h
b/arch/arm64/include/asm/kvm_mmu.h
index 5bfc7ee61997..e915c47744bc 100644
--- a/arch/arm64/include/asm/kvm_mmu.h
+++ b/arch/arm64/include/asm/kvm_mmu.h
@@ -457,19 +457,25 @@ static inline int kvm_write_guest_lock(struct kvm
*kvm, gpa_t gpa,
extern void *__kvm_bp_vect_base;
extern int __kvm_harden_el2_vector_slot;

+#define get_hyp_vector_address(v) \
+({ \
+ void *__v; \
+ if (has_vhe()) \
+ __v = kvm_ksym_ref(v); \
+ else \
+ __v = kern_hyp_va(kvm_ksym_ref_nvhe(v)); \
+ __v; \
+})
+
/* This is called on both VHE and !VHE systems */
static inline void *kvm_get_hyp_vector(void)
{
struct bp_hardening_data *data = arm64_get_bp_hardening_data();
+ void *vect = get_hyp_vector_address(__kvm_hyp_vector);
int slot = -1;
- void *vect = kern_hyp_va(has_vhe()
- ? kvm_ksym_ref(__kvm_hyp_vector)
- : kvm_ksym_ref_nvhe(__kvm_hyp_vector));

if (cpus_have_const_cap(ARM64_HARDEN_BRANCH_PREDICTOR) && data->fn) {
- vect = kern_hyp_va(has_vhe()
- ? kvm_ksym_ref(__bp_harden_hyp_vecs)
- : kvm_ksym_ref_nvhe(__bp_harden_hyp_vecs));
+ vect = get_hyp_vector_address(__bp_harden_hyp_vecs);
slot = data->hyp_vectors_slot;
}

>
> if (cpus_have_const_cap(ARM64_HARDEN_BRANCH_PREDICTOR) && data->fn) {
> - vect = kern_hyp_va(kvm_ksym_ref(__bp_harden_hyp_vecs));
> + vect = kern_hyp_va(has_vhe()
> + ? kvm_ksym_ref(__bp_harden_hyp_vecs)
> + : kvm_ksym_ref_nvhe(__bp_harden_hyp_vecs));
> slot = data->hyp_vectors_slot;
> }
>
> @@ -494,12 +498,11 @@ static inline int kvm_map_vectors(void)
> * HBP + HEL2 -> use hardened vertors and use exec mapping
> */
> if (cpus_have_const_cap(ARM64_HARDEN_BRANCH_PREDICTOR)) {
> - __kvm_bp_vect_base = kvm_ksym_ref(__bp_harden_hyp_vecs);
> - __kvm_bp_vect_base = kern_hyp_va(__kvm_bp_vect_base);
> + __kvm_bp_vect_base =
> kern_hyp_va(kvm_ksym_ref_nvhe(__bp_harden_hyp_vecs));
> }
>
> if (cpus_have_const_cap(ARM64_HARDEN_EL2_VECTORS)) {
> - phys_addr_t vect_pa = __pa_symbol(__bp_harden_hyp_vecs);
> + phys_addr_t vect_pa =
> __pa_symbol(kvm_nvhe_sym(__bp_harden_hyp_vecs));
> unsigned long size = __BP_HARDEN_HYP_VECS_SZ;
>
> /*
> @@ -518,7 +521,8 @@ static inline int kvm_map_vectors(void)
> #else
> static inline void *kvm_get_hyp_vector(void)
> {
> - return kern_hyp_va(kvm_ksym_ref(__kvm_hyp_vector));
> + return kern_hyp_va(has_vhe() ? kvm_ksym_ref(__kvm_hyp_vector)
> + : kvm_ksym_ref_nvhe(__kvm_hyp_vector));
> }
>
> static inline int kvm_map_vectors(void)
> diff --git a/arch/arm64/include/asm/mmu.h
> b/arch/arm64/include/asm/mmu.h
> index 68140fdd89d6..4d913f6dd366 100644
> --- a/arch/arm64/include/asm/mmu.h
> +++ b/arch/arm64/include/asm/mmu.h
> @@ -42,13 +42,6 @@ struct bp_hardening_data {
> bp_hardening_cb_t fn;
> };
>
> -#if (defined(CONFIG_HARDEN_BRANCH_PREDICTOR) || \
> - defined(CONFIG_HARDEN_EL2_VECTORS))
> -
> -extern char __bp_harden_hyp_vecs[];
> -extern atomic_t arm64_el2_vector_last_slot;
> -#endif /* CONFIG_HARDEN_BRANCH_PREDICTOR || CONFIG_HARDEN_EL2_VECTORS
> */
> -
> #ifdef CONFIG_HARDEN_BRANCH_PREDICTOR
> DECLARE_PER_CPU_READ_MOSTLY(struct bp_hardening_data,
> bp_hardening_data);
>
> diff --git a/arch/arm64/kernel/cpu_errata.c
> b/arch/arm64/kernel/cpu_errata.c
> index ad06d6802d2e..318b76a62c56 100644
> --- a/arch/arm64/kernel/cpu_errata.c
> +++ b/arch/arm64/kernel/cpu_errata.c
> @@ -117,7 +117,9 @@ DEFINE_PER_CPU_READ_MOSTLY(struct
> bp_hardening_data, bp_hardening_data);
> static void __copy_hyp_vect_bpi(int slot, const char *hyp_vecs_start,
> const char *hyp_vecs_end)
> {
> - void *dst = lm_alias(__bp_harden_hyp_vecs + slot * SZ_2K);
> + char *vec = has_vhe() ? __bp_harden_hyp_vecs
> + : kvm_nvhe_sym(__bp_harden_hyp_vecs);

If we get this construct often, then something that abstracts
the uggliness of the symbol duality would be nice...

> + void *dst = lm_alias(vec + slot * SZ_2K);
> int i;
>
> for (i = 0; i < SZ_2K; i += 0x80)
> diff --git a/arch/arm64/kernel/image-vars.h
> b/arch/arm64/kernel/image-vars.h
> index 89affa38b143..dc7ee85531f5 100644
> --- a/arch/arm64/kernel/image-vars.h
> +++ b/arch/arm64/kernel/image-vars.h
> @@ -61,9 +61,11 @@ __efistub__ctype = _ctype;
> * memory mappings.
> */
>
> +__kvm_nvhe___guest_exit = __guest_exit;
> __kvm_nvhe___kvm_enable_ssbs = __kvm_enable_ssbs;
> __kvm_nvhe___kvm_flush_vm_context = __kvm_flush_vm_context;
> __kvm_nvhe___kvm_get_mdcr_el2 = __kvm_get_mdcr_el2;
> +__kvm_nvhe___kvm_handle_stub_hvc = __kvm_handle_stub_hvc;
> __kvm_nvhe___kvm_timer_set_cntvoff = __kvm_timer_set_cntvoff;
> __kvm_nvhe___kvm_tlb_flush_local_vmid = __kvm_tlb_flush_local_vmid;
> __kvm_nvhe___kvm_tlb_flush_vmid = __kvm_tlb_flush_vmid;
> @@ -75,6 +77,16 @@ __kvm_nvhe___vgic_v3_read_vmcr =
> __vgic_v3_read_vmcr;
> __kvm_nvhe___vgic_v3_restore_aprs = __vgic_v3_restore_aprs;
> __kvm_nvhe___vgic_v3_save_aprs = __vgic_v3_save_aprs;
> __kvm_nvhe___vgic_v3_write_vmcr = __vgic_v3_write_vmcr;
> +__kvm_nvhe_abort_guest_exit_end = abort_guest_exit_end;
> +__kvm_nvhe_abort_guest_exit_start = abort_guest_exit_start;
> +__kvm_nvhe_arm64_enable_wa2_handling = arm64_enable_wa2_handling;
> +__kvm_nvhe_arm64_ssbd_callback_required =
> arm64_ssbd_callback_required;
> +__kvm_nvhe_hyp_panic = hyp_panic;
> +__kvm_nvhe_kimage_voffset = kimage_voffset;
> +__kvm_nvhe_kvm_host_data = kvm_host_data;
> +__kvm_nvhe_kvm_patch_vector_branch = kvm_patch_vector_branch;
> +__kvm_nvhe_kvm_update_va_mask = kvm_update_va_mask;
> +__kvm_nvhe_panic = panic;
>
> #endif /* CONFIG_KVM */
>
> diff --git a/arch/arm64/kvm/hyp/hyp-entry.S
> b/arch/arm64/kvm/hyp/hyp-entry.S
> index d362fad97cc8..7e3c72fa634f 100644
> --- a/arch/arm64/kvm/hyp/hyp-entry.S
> +++ b/arch/arm64/kvm/hyp/hyp-entry.S
> @@ -40,6 +40,7 @@ el1_sync: // Guest trapped into EL2
> ccmp x0, #ESR_ELx_EC_HVC32, #4, ne
> b.ne el1_trap
>
> +#ifdef __KVM_NVHE_HYPERVISOR__
> mrs x1, vttbr_el2 // If vttbr is valid, the guest
> cbnz x1, el1_hvc_guest // called HVC
>
> @@ -74,6 +75,7 @@ el1_sync: // Guest trapped into EL2
>
> eret
> sb
> +#endif /* __KVM_NVHE_HYPERVISOR__ */
>
> el1_hvc_guest:
> /*
> diff --git a/arch/arm64/kvm/hyp/nvhe/Makefile
> b/arch/arm64/kvm/hyp/nvhe/Makefile
> index 7d64235dba62..c68801e24950 100644
> --- a/arch/arm64/kvm/hyp/nvhe/Makefile
> +++ b/arch/arm64/kvm/hyp/nvhe/Makefile
> @@ -7,7 +7,7 @@ asflags-y := -D__KVM_NVHE_HYPERVISOR__
> ccflags-y := -D__KVM_NVHE_HYPERVISOR__ -fno-stack-protector \
> -DDISABLE_BRANCH_PROFILING $(DISABLE_STACKLEAK_PLUGIN)
>
> -obj-y :=
> +obj-y := ../hyp-entry.o
>
> obj-y := $(patsubst %.o,%.hyp.o,$(obj-y))
> extra-y := $(patsubst %.hyp.o,%.hyp.tmp.o,$(obj-y))
> diff --git a/arch/arm64/kvm/va_layout.c b/arch/arm64/kvm/va_layout.c
> index a4f48c1ac28c..157d106235f7 100644
> --- a/arch/arm64/kvm/va_layout.c
> +++ b/arch/arm64/kvm/va_layout.c
> @@ -150,7 +150,7 @@ void kvm_patch_vector_branch(struct alt_instr *alt,
> /*
> * Compute HYP VA by using the same computation as kern_hyp_va()
> */
> - addr = (uintptr_t)kvm_ksym_ref(__kvm_hyp_vector);
> + addr = (uintptr_t)kvm_ksym_ref_nvhe(__kvm_hyp_vector);
> addr &= va_mask;
> addr |= tag_val << tag_lsb;

Thanks,

M.
--
Jazz is not dead. It just smells funny...