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ANDROID: KVM: arm64: Add support for custom hypercall registration

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When pKVM is in use, allow pKVM modules to register custom hypercall
handlers:

   * pkvm_register_el2_call(): Give a handler to the hypervisor and gets in
     return the newly registered hypercall number.

   * pkvm_el2_mod_call(): Call the previously registered hypercall handler.

There is a limit of 128 hypercalls that can be registered.

Bug: 357781595
Bug: 244543039
Bug: 244373730
Change-Id: I3d6c89675efe5f65f6b53c3b45ae155d1a00164c
Signed-off-by: Vincent Donnefort <vdonnefort@google.com>
Signed-off-by: Quentin Perret <qperret@google.com>
This commit is contained in:
Vincent Donnefort
2022-09-27 17:15:49 +01:00
committed by Keir Fraser
parent d5853c90aa
commit a871b30b2d
6 changed files with 141 additions and 2 deletions
Download Patch File Download Diff File Expand all files Collapse all files
arch/arm64/include/asm/kvm_asm.h
+7
View File
@@ -97,6 +97,13 @@ enum __kvm_host_smccc_func {
__KVM_HOST_SMCCC_FUNC___pkvm_swap_reader_tracing,
__KVM_HOST_SMCCC_FUNC___pkvm_enable_event,
__KVM_HOST_SMCCC_FUNC___pkvm_selftest_event,
__KVM_HOST_SMCCC_FUNC___pkvm_register_hcall,
/*
* Start of the dynamically registered hypercalls. Start a bit
* further, just in case some modules...
*/
__KVM_HOST_SMCCC_FUNC___dynamic_hcalls = 128,
};
#define DECLARE_KVM_VHE_SYM(sym) extern char sym[]
arch/arm64/include/asm/kvm_pkvm_module.h
+25 -1
View File
@@ -6,6 +6,8 @@
#include <asm/kvm_pgtable.h>
#include <linux/export.h>
typedef void (*dyn_hcall_t)(struct user_pt_regs *);
struct pkvm_module_ops {
int (*create_private_mapping)(phys_addr_t phys, size_t size,
enum kvm_pgtable_prot prot,
@@ -33,10 +35,12 @@ struct pkvm_el2_module {
int (*init)(const struct pkvm_module_ops *ops);
};
#ifdef MODULE
int __pkvm_load_el2_module(struct pkvm_el2_module *mod, struct module *this,
unsigned long *token);
int __pkvm_register_el2_call(dyn_hcall_t hfn, unsigned long token,
unsigned long hyp_text_kern_va);
#ifdef MODULE
#define pkvm_load_el2_module(init_fn, token) \
({ \
extern char __kvm_nvhe___hypmod_text_start[]; \
@@ -66,5 +70,25 @@ int __pkvm_load_el2_module(struct pkvm_el2_module *mod, struct module *this,
\
__pkvm_load_el2_module(&mod, THIS_MODULE, token); \
})
#define pkvm_register_el2_mod_call(hfn, token) \
({ \
extern char __kvm_nvhe___hypmod_text_start[]; \
unsigned long hyp_text_kern_va = \
(unsigned long)__kvm_nvhe___hypmod_text_start; \
__pkvm_register_el2_call(hfn, token, \
hyp_text_kern_va); \
})
#define pkvm_el2_mod_call(id, ...) \
({ \
struct arm_smccc_res res; \
\
arm_smccc_1_1_hvc(KVM_HOST_SMCCC_ID(id), \
##__VA_ARGS__, &res); \
WARN_ON(res.a0 != SMCCC_RET_SUCCESS); \
\
res.a1; \
})
#endif
#endif
arch/arm64/kvm/hyp/include/nvhe/modules.h
+13
View File
@@ -1,5 +1,18 @@
#include <asm/kvm_pgtable.h>
#define HCALL_HANDLED 0
#define HCALL_UNHANDLED -1
#ifdef CONFIG_MODULES
int __pkvm_init_module(void *module_init);
int __pkvm_register_hcall(unsigned long hfn_hyp_va);
int handle_host_dynamic_hcall(struct kvm_cpu_context *host_ctxt);
#else
static inline int __pkvm_init_module(void *module_init) { return -EOPNOTSUPP; }
static inline int
__pkvm_register_hcall(unsigned long hfn_hyp_va) { return -EOPNOTSUPP; }
static inline int handle_host_dynamic_hcall(struct kvm_cpu_context *host_ctxt)
{
return HCALL_UNHANDLED;
}
#endif
arch/arm64/kvm/hyp/nvhe/hyp-main.c
+11
View File
@@ -1311,6 +1311,13 @@ static void handle___pkvm_init_module(struct kvm_cpu_context *host_ctxt)
cpu_reg(host_ctxt, 1) = __pkvm_init_module(ptr);
}
static void handle___pkvm_register_hcall(struct kvm_cpu_context *host_ctxt)
{
DECLARE_REG(unsigned long, hfn_hyp_va, host_ctxt, 1);
cpu_reg(host_ctxt, 1) = __pkvm_register_hcall(hfn_hyp_va);
}
typedef void (*hcall_t)(struct kvm_cpu_context *);
#define HANDLE_FUNC(x) [__KVM_HOST_SMCCC_FUNC_##x] = (hcall_t)handle_##x
@@ -1360,6 +1367,7 @@ static const hcall_t host_hcall[] = {
HANDLE_FUNC(__pkvm_map_module_page),
HANDLE_FUNC(__pkvm_unmap_module_page),
HANDLE_FUNC(__pkvm_init_module),
HANDLE_FUNC(__pkvm_register_hcall),
};
static void handle_host_hcall(struct kvm_cpu_context *host_ctxt)
@@ -1368,6 +1376,9 @@ static void handle_host_hcall(struct kvm_cpu_context *host_ctxt)
unsigned long hcall_min = 0;
hcall_t hfn;
if (handle_host_dynamic_hcall(host_ctxt) == HCALL_HANDLED)
return;
/*
* If pKVM has been initialised then reject any calls to the
* early "privileged" hypercalls. Note that we cannot reject
arch/arm64/kvm/hyp/nvhe/modules.c
+70 -1
View File
@@ -8,6 +8,8 @@
#include <nvhe/modules.h>
#include <nvhe/mm.h>
#include <nvhe/serial.h>
#include <nvhe/spinlock.h>
#include <nvhe/trap_handler.h>
const struct pkvm_module_ops module_ops = {
.create_private_mapping = __pkvm_create_private_mapping,
@@ -23,6 +25,73 @@ int __pkvm_init_module(void *module_init)
int ret;
ret = do_module_init(&module_ops);
return ret;
}
#define MAX_DYNAMIC_HCALLS 128
atomic_t num_dynamic_hcalls = ATOMIC_INIT(0);
DEFINE_HYP_SPINLOCK(dyn_hcall_lock);
static dyn_hcall_t host_dynamic_hcalls[MAX_DYNAMIC_HCALLS];
int handle_host_dynamic_hcall(struct kvm_cpu_context *host_ctxt)
{
DECLARE_REG(unsigned long, id, host_ctxt, 0);
dyn_hcall_t hfn;
int dyn_id;
/*
* TODO: static key to protect when no dynamic hcall is registered?
*/
dyn_id = (int)(id - KVM_HOST_SMCCC_ID(0)) -
__KVM_HOST_SMCCC_FUNC___dynamic_hcalls;
if (dyn_id < 0)
return HCALL_UNHANDLED;
cpu_reg(host_ctxt, 0) = SMCCC_RET_NOT_SUPPORTED;
/*
* Order access to num_dynamic_hcalls and host_dynamic_hcalls. Paired
* with __pkvm_register_hcall().
*/
if (dyn_id >= atomic_read_acquire(&num_dynamic_hcalls))
goto end;
hfn = READ_ONCE(host_dynamic_hcalls[dyn_id]);
if (!hfn)
goto end;
cpu_reg(host_ctxt, 0) = SMCCC_RET_SUCCESS;
hfn(&host_ctxt->regs);
end:
return HCALL_HANDLED;
}
int __pkvm_register_hcall(unsigned long hvn_hyp_va)
{
dyn_hcall_t hfn = (void *)hvn_hyp_va;
int reserved_id;
hyp_spin_lock(&dyn_hcall_lock);
reserved_id = atomic_read(&num_dynamic_hcalls);
if (reserved_id >= MAX_DYNAMIC_HCALLS) {
hyp_spin_unlock(&dyn_hcall_lock);
return -ENOMEM;
}
WRITE_ONCE(host_dynamic_hcalls[reserved_id], hfn);
/*
* Order access to num_dynamic_hcalls and host_dynamic_hcalls. Paired
* with handle_host_dynamic_hcall.
*/
atomic_set_release(&num_dynamic_hcalls, reserved_id + 1);
hyp_spin_unlock(&dyn_hcall_lock);
return reserved_id + __KVM_HOST_SMCCC_FUNC___dynamic_hcalls;
};
arch/arm64/kvm/pkvm.c
+15
View File
@@ -637,3 +637,18 @@ int __pkvm_load_el2_module(struct pkvm_el2_module *mod, struct module *this,
return 0;
}
EXPORT_SYMBOL(__pkvm_load_el2_module);
int __pkvm_register_el2_call(dyn_hcall_t hfn, unsigned long token,
unsigned long hyp_text_kern_va)
{
unsigned long hfn_hyp_va, offset, text_hyp_va = token;
int ret;
offset = (unsigned long)hfn - hyp_text_kern_va;
hfn_hyp_va = text_hyp_va + offset;
ret = kvm_call_hyp_nvhe(__pkvm_register_hcall,
(unsigned long)hfn_hyp_va);
return ret;
}
EXPORT_SYMBOL(__pkvm_register_el2_call);