Arm CCA Realms cannot issue Hyper-V hypercalls via HVC; the guest must route them through the RSI_HOST_CALL interface, which takes the IPA of a per-CPU rsi_host_call structure as its argument.
Add hyperv_pcpu_hostcall_struct as a per-CPU pointer to that buffer and allocate it for the boot CPU during hyperv_init() and for each secondary CPU in hv_cpu_init(). The allocation is gated on is_realm_world() so non-Realm arm64 Hyper-V guests pay no memory cost. Signed-off-by: Kameron Carr <[email protected]> --- arch/arm64/hyperv/mshyperv.c | 78 ++++++++++++++++++++++++++++++- arch/arm64/include/asm/mshyperv.h | 3 ++ 2 files changed, 79 insertions(+), 2 deletions(-) diff --git a/arch/arm64/hyperv/mshyperv.c b/arch/arm64/hyperv/mshyperv.c index 4fdc26ade1d74..08fec82691683 100644 --- a/arch/arm64/hyperv/mshyperv.c +++ b/arch/arm64/hyperv/mshyperv.c @@ -15,10 +15,16 @@ #include <linux/errno.h> #include <linux/version.h> #include <linux/cpuhotplug.h> +#include <linux/slab.h> +#include <linux/percpu.h> #include <asm/mshyperv.h> +#include <asm/rsi.h> static bool hyperv_initialized; +void * __percpu *hyperv_pcpu_hostcall_struct; +EXPORT_SYMBOL_GPL(hyperv_pcpu_hostcall_struct); + int hv_get_hypervisor_version(union hv_hypervisor_version_info *info) { hv_get_vpreg_128(HV_REGISTER_HYPERVISOR_VERSION, @@ -60,6 +66,46 @@ static bool __init hyperv_detect_via_acpi(void) #endif +static void hv_hostcall_free(void) +{ + int cpu; + + if (!hyperv_pcpu_hostcall_struct) + return; + + for_each_possible_cpu(cpu) + kfree(*per_cpu_ptr(hyperv_pcpu_hostcall_struct, cpu)); + free_percpu(hyperv_pcpu_hostcall_struct); + hyperv_pcpu_hostcall_struct = NULL; +} + +static int hv_cpu_init(unsigned int cpu) +{ + void **hostcall_struct; + gfp_t flags; + void *mem; + + if (hyperv_pcpu_hostcall_struct) { + /* hv_cpu_init() can be called with IRQs disabled from hv_resume() */ + flags = irqs_disabled() ? GFP_ATOMIC : GFP_KERNEL; + + hostcall_struct = (void **)this_cpu_ptr(hyperv_pcpu_hostcall_struct); + /* + * The hostcall_struct memory is not freed when the CPU + * goes offline. If a previously offlined CPU is brought + * back online, the memory is reused here. + */ + if (!*hostcall_struct) { + mem = kzalloc_obj(struct rsi_host_call, flags); + if (!mem) + return -ENOMEM; + *hostcall_struct = mem; + } + } + + return hv_common_cpu_init(cpu); +} + static bool __init hyperv_detect_via_smccc(void) { uuid_t hyperv_uuid = UUID_INIT( @@ -73,6 +119,8 @@ static bool __init hyperv_detect_via_smccc(void) static int __init hyperv_init(void) { struct hv_get_vp_registers_output result; + void **hostcall_struct; + void *mem; u64 guest_id; int ret; @@ -85,6 +133,27 @@ static int __init hyperv_init(void) if (!hyperv_detect_via_acpi() && !hyperv_detect_via_smccc()) return 0; + /* + * The RSI host-call buffer is only ever used when + * is_realm_world() is true. Skip the per-CPU allocation on + * non-Realm guests. + */ + if (is_realm_world()) { + hyperv_pcpu_hostcall_struct = alloc_percpu(void *); + if (!hyperv_pcpu_hostcall_struct) + return -ENOMEM; + + hostcall_struct = (void **)this_cpu_ptr(hyperv_pcpu_hostcall_struct); + if (!*hostcall_struct) { + mem = kzalloc_obj(struct rsi_host_call); + if (!mem) { + ret = -ENOMEM; + goto free_hostcall_mem; + } + *hostcall_struct = mem; + } + } + /* Setup the guest ID */ guest_id = hv_generate_guest_id(LINUX_VERSION_CODE); hv_set_vpreg(HV_REGISTER_GUEST_OS_ID, guest_id); @@ -106,12 +175,13 @@ static int __init hyperv_init(void) ret = hv_common_init(); if (ret) - return ret; + goto free_hostcall_mem; ret = cpuhp_setup_state(CPUHP_AP_HYPERV_ONLINE, "arm64/hyperv_init:online", - hv_common_cpu_init, hv_common_cpu_die); + hv_cpu_init, hv_common_cpu_die); if (ret < 0) { hv_common_free(); + hv_hostcall_free(); return ret; } @@ -125,6 +195,10 @@ static int __init hyperv_init(void) hyperv_initialized = true; return 0; + +free_hostcall_mem: + hv_hostcall_free(); + return ret; } early_initcall(hyperv_init); diff --git a/arch/arm64/include/asm/mshyperv.h b/arch/arm64/include/asm/mshyperv.h index b721d3134ab66..65a00bd14c6cb 100644 --- a/arch/arm64/include/asm/mshyperv.h +++ b/arch/arm64/include/asm/mshyperv.h @@ -63,4 +63,7 @@ static inline u64 hv_get_non_nested_msr(unsigned int reg) #include <asm-generic/mshyperv.h> +/* Per-CPU RSI host call structure for CCA Realms */ +extern void *__percpu *hyperv_pcpu_hostcall_struct; + #endif -- 2.45.4
