On 8/21/25 12:55 AM, Steven Price wrote:
Query the RMI version number and check if it is a compatible version. A
static key is also provided to signal that a supported RMM is available.
Functions are provided to query if a VM or VCPU is a realm (or rec)
which currently will always return false.
Later patches make use of struct realm and the states as the ioctls
interfaces are added to support realm and REC creation and destruction.
Reviewed-by: Gavin Shan <gshan@xxxxxxxxxx>
Reviewed-by: Suzuki K Poulose <suzuki.poulose@xxxxxxx>
Signed-off-by: Steven Price <steven.price@xxxxxxx>
---
Changes since v8:
* No need to guard kvm_init_rme() behind 'in_hyp_mode'.
Changes since v6:
* Improved message for an unsupported RMI ABI version.
Changes since v5:
* Reword "unsupported" message from "host supports" to "we want" to
clarify that 'we' are the 'host'.
Changes since v2:
* Drop return value from kvm_init_rme(), it was always 0.
* Rely on the RMM return value to identify whether the RSI ABI is
compatible.
---
arch/arm64/include/asm/kvm_emulate.h | 18 +++++++++
arch/arm64/include/asm/kvm_host.h | 4 ++
arch/arm64/include/asm/kvm_rme.h | 56 ++++++++++++++++++++++++++++
arch/arm64/include/asm/virt.h | 1 +
arch/arm64/kvm/Makefile | 2 +-
arch/arm64/kvm/arm.c | 5 +++
arch/arm64/kvm/rme.c | 56 ++++++++++++++++++++++++++++
7 files changed, 141 insertions(+), 1 deletion(-)
create mode 100644 arch/arm64/include/asm/kvm_rme.h
create mode 100644 arch/arm64/kvm/rme.c
[...]
diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index 888f7c7abf54..76177c56f1ef 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -40,6 +40,7 @@
#include <asm/kvm_nested.h>
#include <asm/kvm_pkvm.h>
#include <asm/kvm_ptrauth.h>
+#include <asm/kvm_rme.h>
#include <asm/sections.h>
Nit: The header file <asm/kvm_rme.h> has been included to <asm/kvm_host.h> and
<linux/kvm_host.h>, which has been included to arm.c. So this explicit inclusion
can be dropped.
#include <kvm/arm_hypercalls.h>
@@ -59,6 +60,8 @@ enum kvm_wfx_trap_policy {
static enum kvm_wfx_trap_policy kvm_wfi_trap_policy __read_mostly = KVM_WFX_NOTRAP_SINGLE_TASK;
static enum kvm_wfx_trap_policy kvm_wfe_trap_policy __read_mostly = KVM_WFX_NOTRAP_SINGLE_TASK;
+DEFINE_STATIC_KEY_FALSE(kvm_rme_is_available);
+
DECLARE_KVM_HYP_PER_CPU(unsigned long, kvm_hyp_vector);
DEFINE_PER_CPU(unsigned long, kvm_arm_hyp_stack_base);
@@ -2836,6 +2839,8 @@ static __init int kvm_arm_init(void)
in_hyp_mode = is_kernel_in_hyp_mode();
+ kvm_init_rme();
+
if (cpus_have_final_cap(ARM64_WORKAROUND_DEVICE_LOAD_ACQUIRE) ||
cpus_have_final_cap(ARM64_WORKAROUND_1508412))
kvm_info("Guests without required CPU erratum workarounds can deadlock system!\n" \
diff --git a/arch/arm64/kvm/rme.c b/arch/arm64/kvm/rme.c
new file mode 100644
index 000000000000..67cf2d94cb2d
--- /dev/null
+++ b/arch/arm64/kvm/rme.c
@@ -0,0 +1,56 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2023 ARM Ltd.
+ */
+
+#include <linux/kvm_host.h>
+
+#include <asm/rmi_cmds.h>
+#include <asm/virt.h>
+
+static int rmi_check_version(void)
+{
+ struct arm_smccc_res res;
+ unsigned short version_major, version_minor;
+ unsigned long host_version = RMI_ABI_VERSION(RMI_ABI_MAJOR_VERSION,
+ RMI_ABI_MINOR_VERSION);
+
+ arm_smccc_1_1_invoke(SMC_RMI_VERSION, host_version, &res);
+
+ if (res.a0 == SMCCC_RET_NOT_SUPPORTED)
+ return -ENXIO;
+
+ version_major = RMI_ABI_VERSION_GET_MAJOR(res.a1);
+ version_minor = RMI_ABI_VERSION_GET_MINOR(res.a1);
+
+ if (res.a0 != RMI_SUCCESS) {
+ unsigned short high_version_major, high_version_minor;
+
+ high_version_major = RMI_ABI_VERSION_GET_MAJOR(res.a2);
+ high_version_minor = RMI_ABI_VERSION_GET_MINOR(res.a2);
+
+ kvm_err("Unsupported RMI ABI (v%d.%d - v%d.%d) we want v%d.%d\n",
+ version_major, version_minor,
+ high_version_major, high_version_minor,
+ RMI_ABI_MAJOR_VERSION,
+ RMI_ABI_MINOR_VERSION);
+ return -ENXIO;
+ }
+
+ kvm_info("RMI ABI version %d.%d\n", version_major, version_minor);
+
+ return 0;
+}
+
+void kvm_init_rme(void)
+{
+ if (PAGE_SIZE != SZ_4K)
+ /* Only 4k page size on the host is supported */
+ return;
Nit: The comment can be moved before the check, something like below. Otherwise,
{} is needed here.
/* Only 4kB page size is supported */
if (PAGE_SIZE != SZ_4K)
return;
+
+ if (rmi_check_version())
+ /* Continue without realm support */
+ return;
Nit: same as above.
+
+ /* Future patch will enable static branch kvm_rme_is_available */
+}
Thanks,
Gavin
