[PATCH 01/15] arm64: kvm: Unify users of HVC instruction

David Brazdil
2020-04-30T14:48:51Z

From: Quentin Perret <qperret@google.com>

Currently, the arm64 KVM code provides __kvm_call_hyp assembly procedure which
does nothing but call the HVC instruction. This is used to call functions by
their pointer in EL2 under nVHE, and abused by __cpu_init_hyp_mode to pass
a data pointer. The hyp-stub code, on the other hand, has its own assembly
procedures for (re)setting hyp vectors.

In preparation for a clean-up of the KVM hypercall interface, unify all HVC
users behind __kvm_call_hyp and remove comments about expected meaning of
arguments.

No functional changes intended.

Signed-off-by: Quentin Perret <qperret@google.com>
Signed-off-by: David Brazdil <dbrazdil@google.com>
---
arch/arm64/include/asm/kvm_host.h | 12 ++++++-----
arch/arm64/include/asm/virt.h | 33 ++++++++++++++++++++++++++++--
arch/arm64/kernel/hyp-stub.S | 34 -------------------------------
arch/arm64/kvm/hyp.S | 13 +-----------
4 files changed, 39 insertions(+), 53 deletions(-)

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 32c8a675e5a4..e61143d6602d 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -25,6 +25,7 @@
#include <asm/kvm.h>
#include <asm/kvm_asm.h>
#include <asm/thread_info.h>
+#include <asm/virt.h>

#define __KVM_HAVE_ARCH_INTC_INITIALIZED

@@ -446,7 +447,8 @@ int kvm_test_age_hva(struct kvm *kvm, unsigned long hva);
void kvm_arm_halt_guest(struct kvm *kvm);
void kvm_arm_resume_guest(struct kvm *kvm);

-u64 __kvm_call_hyp(void *hypfn, ...);
+#define kvm_call_hyp_nvhe(hypfn, ...) \
+ __kvm_call_hyp((unsigned long)kvm_ksym_ref(hypfn), ##__VA_ARGS__)

/*
* The couple of isb() below are there to guarantee the same behaviour
@@ -459,7 +461,7 @@ u64 __kvm_call_hyp(void *hypfn, ...);
f(__VA_ARGS__); \
isb(); \
} else { \
- __kvm_call_hyp(kvm_ksym_ref(f), ##__VA_ARGS__); \
+ kvm_call_hyp_nvhe(f, ##__VA_ARGS__); \
} \
} while(0)

@@ -471,8 +473,7 @@ u64 __kvm_call_hyp(void *hypfn, ...);
ret = f(__VA_ARGS__); \
isb(); \
} else { \
- ret = __kvm_call_hyp(kvm_ksym_ref(f), \
- ##__VA_ARGS__); \
+ ret = kvm_call_hyp_nvhe(f, ##__VA_ARGS__); \
} \
\
ret; \
@@ -551,7 +552,8 @@ static inline void __cpu_init_hyp_mode(phys_addr_t pgd_ptr,
* cpus_have_const_cap() wrapper.
*/
BUG_ON(!system_capabilities_finalized());
- __kvm_call_hyp((void *)pgd_ptr, hyp_stack_ptr, vector_ptr, tpidr_el2);
+ __kvm_call_hyp((unsigned long)pgd_ptr, hyp_stack_ptr, vector_ptr,
+ tpidr_el2);

/*
* Disabling SSBD on a non-VHE system requires us to enable SSBS
diff --git a/arch/arm64/include/asm/virt.h b/arch/arm64/include/asm/virt.h
index 61fd26752adc..fdc11f819b06 100644
--- a/arch/arm64/include/asm/virt.h
+++ b/arch/arm64/include/asm/virt.h
@@ -62,8 +62,37 @@
*/
extern u32 __boot_cpu_mode[2];

-void __hyp_set_vectors(phys_addr_t phys_vector_base);
-void __hyp_reset_vectors(void);
+/* Make HVC call into the hypervisor. */
+extern u64 __kvm_call_hyp(unsigned long arg, ...);
+
+/*
+ * __hyp_set_vectors: Call this after boot to set the initial hypervisor
+ * vectors as part of hypervisor installation. On an SMP system, this should
+ * be called on each CPU.
+ *
+ * @phys_vector_base must be the physical address of the new vector table, and
+ * must be 2KB aligned.
+ *
+ * Before calling this, you must check that the stub hypervisor is installed
+ * everywhere, by waiting for any secondary CPUs to be brought up and then
+ * checking that is_hyp_mode_available() is true.
+ *
+ * If not, there is a pre-existing hypervisor, some CPUs failed to boot, or
+ * something else went wrong... in such cases, trying to install a new
+ * hypervisor is unlikely to work as desired.
+ *
+ * When you call into your shiny new hypervisor, sp_el2 will contain junk,
+ * so you will need to set that to something sensible at the new hypervisor's
+ * initialisation entry point.
+ */
+static inline void __hyp_set_vectors(phys_addr_t phys_vector_base)
+{
+ __kvm_call_hyp(HVC_SET_VECTORS, phys_vector_base);
+}
+static inline void __hyp_reset_vectors(void)
+{
+ __kvm_call_hyp(HVC_RESET_VECTORS);
+}

/* Reports the availability of HYP mode */
static inline bool is_hyp_mode_available(void)
diff --git a/arch/arm64/kernel/hyp-stub.S b/arch/arm64/kernel/hyp-stub.S
index e473ead806ed..78d4ec5c4290 100644
--- a/arch/arm64/kernel/hyp-stub.S
+++ b/arch/arm64/kernel/hyp-stub.S
@@ -84,37 +84,3 @@ ENDPROC(\label)
invalid_vector el1_irq_invalid
invalid_vector el1_fiq_invalid
invalid_vector el1_error_invalid
-
-/*
- * __hyp_set_vectors: Call this after boot to set the initial hypervisor
- * vectors as part of hypervisor installation. On an SMP system, this should
- * be called on each CPU.
- *
- * x0 must be the physical address of the new vector table, and must be
- * 2KB aligned.
- *
- * Before calling this, you must check that the stub hypervisor is installed
- * everywhere, by waiting for any secondary CPUs to be brought up and then
- * checking that is_hyp_mode_available() is true.
- *
- * If not, there is a pre-existing hypervisor, some CPUs failed to boot, or
- * something else went wrong... in such cases, trying to install a new
- * hypervisor is unlikely to work as desired.
- *
- * When you call into your shiny new hypervisor, sp_el2 will contain junk,
- * so you will need to set that to something sensible at the new hypervisor's
- * initialisation entry point.
- */
-
-ENTRY(__hyp_set_vectors)
- mov x1, x0
- mov x0, #HVC_SET_VECTORS
- hvc #0
- ret
-ENDPROC(__hyp_set_vectors)
-
-ENTRY(__hyp_reset_vectors)
- mov x0, #HVC_RESET_VECTORS
- hvc #0
- ret
-ENDPROC(__hyp_reset_vectors)
diff --git a/arch/arm64/kvm/hyp.S b/arch/arm64/kvm/hyp.S
index 3c79a1124af2..f6c9501ddfc9 100644
--- a/arch/arm64/kvm/hyp.S
+++ b/arch/arm64/kvm/hyp.S
@@ -11,22 +11,11 @@
#include <asm/cpufeature.h>

/*
- * u64 __kvm_call_hyp(void *hypfn, ...);
+ * u64 __kvm_call_hyp(unsigned long arg, ...);
*
* This is not really a variadic function in the classic C-way and care must
* be taken when calling this to ensure parameters are passed in registers
* only, since the stack will change between the caller and the callee.
- *
- * Call the function with the first argument containing a pointer to the
- * function you wish to call in Hyp mode, and subsequent arguments will be
- * passed as x0, x1, and x2 (a maximum of 3 arguments in addition to the
- * function pointer can be passed). The function being called must be mapped
- * in Hyp mode (see init_hyp_mode in arch/arm/kvm/arm.c). Return values are
- * passed in x0.
- *
- * A function pointer with a value less than 0xfff has a special meaning,
- * and is used to implement hyp stubs in the same way as in
- * arch/arm64/kernel/hyp_stub.S.
*/
SYM_FUNC_START(__kvm_call_hyp)
hvc #0
--
2.26.1