[PATCH v19 05/20] KVM: arm64: Track the type of VM in kvm_arch
Gavin Shan
gshan at redhat.com
Wed Sep 23 06:23:18 PDT 2026
On 9/23/26 8:24 PM, Suzuki K Poulose wrote:
> On 23/09/2026 07:19, Gavin Shan wrote:
>> On 9/23/26 4:05 PM, Gavin Shan wrote:
>>> On 9/21/26 7:28 AM, Suzuki K Poulose wrote:
>>>> KVM arm64 has different types of VMs with all the different modes in which
>>>> the hypervisor code can be run. e.g., VHE, nVHE, pKVM etc. Then there is
>>>> protected VM and normal VMs with pKVM. We might soon add other types,
>>>> e.g., Arm CCA Realm. So in an effort to make the handling of these
>>>> different types of VMs a bit more friendly to the eyes, add a VM flavor to
>>>> the kvm_arch and we could then add handlers for different operations based
>>>> on the VM type.
>>>>
>>>> Keep the flavor initialisation at the beginning to allow for the detection
>>>> early enough and fail out on any unsupported requests.
>>>>
>>>> With that, add wrappers for checking the "type" of a VM and replace the
>>>> existing users with the new wrappers.
>>>>
>>>> Given we already have the construct of "kvm_vm_is_protected" in the core
>>>> KVM code, use that for all confidential compute guests including Realms
>>>> that we are about to add.
>>>>
>>>> Adds __VM_PROTECTED marker vm flavor to generalize kvm_vm_is_protected()
>>>> to predicate all confidential guests running on KVM. In later patches, we
>>>> would add Realm VMs, which would also be classified as protected.
>>>>
>>>> Add explicit helper to detect if a given VM is a "protected" VM under pKVM.
>>>> Change the existing users that precisely want to check the VM type. These
>>>> include :
>>>> - kvm_arch_prepare_memory_region - For preventing memslot changes after
>>>> pVM creation.
>>>>
>>>> All the others are retained as a wider check for confidential guest VMs.
>>>> These are:
>>>> - kvm_vm_ioctl_set_counter_offset - For disallowing timer offset
>>>> configuration
>>>> - io_mem_abort for dabt handling without valid syndrome information
>>>>
>>>> Both of which are true for Realms too.
>>>>
>>>> Realms support is restricted to VHE host and thus "kvm_vm_is_protected()"
>>>> checks in the pkvm hyp specific code doesn't need to change, as the only
>>>> protected guests it deals with is "protected pKVM" guests. To tighten this
>>>> init_pkvm_hyp_vm() restricts the hyp copy of the vm_flavor to the ones it
>>>> supports.
>>>>
>>>> Suggested-by: Marc Zyngier <maz at kernel.org>
>>>> Signed-off-by: Suzuki K Poulose <suzuki.poulose at arm.com>
>>>> ---
>>>> Changes since v18:
>>>> - Merge the __VM_PROTECTED marker and the widening of kvm_vm_is_protected()
>>>> to this patch.
>>>> - Merge the use of kvm_vm_is_unprotected_pkvm() for ! kvm_vm_is_protected()
>>>> given the scope changes here.
>>>> - Drop Fuad's review tag, as this patch has multiple merges
>>>> - Restrict the VM flavors to the supported types in init_pkvm_hyp_vm().
>>>> - Drop kvm_vm_hyp_is_pkvm() and revert to is_protected_kvm_enabled()
>>>> - Use is_protected_kvm_enabled() to make the pKVM guest flavor checks.
>>>> - s/PKVM/pKVM for commit descriptions too
>>>>
>>>> Changes since v17:
>>>> * s/PKVM/pKVM for the comments
>>>> * Drop type argument for pkvm_init_host_vm and also drop protected variable.
>>>> * Add helpers for checking if the VM is running on pKVM (kvm_vm_hyp_is_pkvm())
>>>> * Use kvm_vm_hyp_is_pkvm() to replace is_protected_kvm_enabled() with valid
>>>> kvm instance
>>>> ---
>>>> arch/arm64/include/asm/kvm_host.h | 22 +++++++++++++++++++---
>>>> arch/arm64/include/asm/kvm_pkvm.h | 4 ++--
>>>> arch/arm64/kvm/arm.c | 31 ++++++++++++++++++++++++++-----
>>>> arch/arm64/kvm/handle_exit.c | 2 +-
>>>> arch/arm64/kvm/hyp/nvhe/pkvm.c | 6 +++++-
>>>> arch/arm64/kvm/mmu.c | 2 +-
>>>> arch/arm64/kvm/pkvm.c | 6 ++----
>>>> 7 files changed, 56 insertions(+), 17 deletions(-)
>>>>
>>>
>>> This causes broken nVHE mode. I applied PATCH[01-05] to v7.3.rc4 whose head commit
>>> is f0100363d8c3, and kselftests/kvm/guest_print causes host crash (as below). I don't
>>> see the crash if only PATCH[01-04] are applied.
>>>
>>> host$ cat /proc/cmdline | grep kvm-arm\.mode
>>> BOOT_IMAGE=(hd0,gpt2)/vmlinuz-7.3.0-rc4-gavin+ root=/dev/mapper/ rhel_nvidia--grace--hopper--01-root ro crashkernel=2G-4G:406M,4G-64G:470M,64G-:726M rd.lvm.lv=rhel_nvidia- grace-hopper-01/root rd.lvm.lv=rhel_nvidia-grace-hopper-01/swap video=simplefb:off kvm-arm.mode=nvhe
>>>
>>> host$ cd linux/tools/testing/selftests/kvm
>>> host$ ./guest_print_test
>>> Random seed: 0x193a0ed3
>>> [ 192.754328] kvm [6674]: nVHE hyp panic at: [<ffff8000811da044>] __kvm_nvhe___timer_enable_traps+0x4/0x160!
>>> [ 192.754338] kvm [6674]: nVHE call trace:
>>> [ 192.754339] kvm [6674]: [<ffff8000811dcf34>] __kvm_nvhe_hyp_panic+0xb4/0xe0
>>> [ 192.754342] kvm [6674]: [<ffff8000811dcba4>] __kvm_nvhe___kvm_vcpu_run+0x164/0x440
>>> [ 192.754344] kvm [6674]: [<ffff8000811dfe90>] __kvm_nvhe_handle___kvm_vcpu_run+0x40/0x1f0
>>> [ 192.754346] kvm [6674]: [<ffff8000811e0238>] __kvm_nvhe_handle_trap+0x158/0x280
>>> [ 192.754347] kvm [6674]: [<ffff8000811dd8fc>] __kvm_nvhe___skip_pauth_save+0x4/0x4
>>> [ 192.754348] kvm [6674]: ---[ end nVHE call trace ]---
>>> [ 192.754350] Code: d2818002 17fffff7 d503201f f9400001 (b94a6821)
>>> [ 192.754350] kvm [6674]: Hyp Offset: 0xfffeb0d7fe2e0000
>>> [ 192.754351] Kernel panic - not syncing: HYP panic:
>>> [ 192.754351] PS:834003c9 PC:0000cf2882efa044 ESR:0000000096000004
>>> [ 192.754351] FAR:ffff00009b286a68 HPFAR:8000000000000000 PAR:1d00ec7edbadc8de
>>> [ 192.754351] VCPU:0000cf011848a350
>>> [ 192.845154] CPU: 12 UID: 0 PID: 6674 Comm: guest_print_tes Kdump: loaded Not tainted 7.3.0-rc4-gavin+ #7 PREEMPT(full)
>>> [ 192.856182] Hardware name: GH200 P5042, BIOS 02.04.01 20250422
>>> [ 192.862231] Call trace:
>>> [ 192.864725] show_stack+0x20/0x38 (C)
>>> [ 192.868471] dump_stack_lvl+0x88/0xb8
>>> [ 192.872215] dump_stack+0x18/0x30
>>> [ 192.875598] vpanic+0x280/0x498
>>> [ 192.878806] panic+0x68/0x70
>>> [ 192.881745] nvhe_hyp_panic_handler+0x184/0x190
>>> [ 192.886372] kvm_arm_vcpu_enter_exit+0x24/0x100
>>> [ 192.891003] kvm_arch_vcpu_ioctl_run+0x254/0x7c0
>>> [ 192.895726] kvm_vcpu_ioctl+0x174/0xb40
>>> [ 192.899645] __arm64_sys_ioctl+0xb0/0x120
>>> [ 192.903745] invoke_syscall.constprop.0+0xa8/0x100
>>> [ 192.908639] do_el0_svc+0xb8/0xe0
>>> [ 192.912022] el0_svc+0x48/0x1f8
>>> [ 192.915228] el0t_64_sync_handler+0xa0/0xe8
>>> [ 192.919500] el0t_64_sync+0x1ac/0x1b0
>>> [ 192.923243] SMP: stopping secondary CPUs
>>> [ 192.927653] Starting crashdump kernel...
>>> [ 192.931658] Bye!
>>>
>>
>> With the following changes applied after PATCH[01-05] on top of v7.3.rc4, the crash
>> is avoided.
>>
>> In arch/arm64/include/asm/kvm_host.h:
>>
>> -#define kvm_vm_is_protected(kvm) ((kvm)->arch.vm_flavor >= __VM_PROTECTED)
>> +#define kvm_vm_is_protected(kvm) \
>> + (is_protected_kvm_enabled() && (kvm)->arch.vm_flavor >= __VM_PROTECTED)
>
> That only papers over the problem. We can't use the vcpu_is_*
> constructs from nvhe hyp, without converting the vcpu->kvm to
> the hyp address, before accessing it. The fix is a bit more
> involved. One option is to define the vcpu_is_* helpers only
> for the !NVHE hyp code in the kvm_host.h (to avoid pulling
> in the asm/kvm_mmu.h in to kvm_host.h and then make a mess
> with header dependencies) and define the NVHE version in
> asm/kvm_hyp.h. Something like :
>
>
> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
> index 46a7f6c1e426c..4016d09ed39c3 100644
> --- a/arch/arm64/include/asm/kvm_host.h
> +++ b/arch/arm64/include/asm/kvm_host.h
> @@ -1545,11 +1545,14 @@ struct kvm *kvm_arch_alloc_vm(void);
> #define __KVM_HAVE_ARCH_FLUSH_REMOTE_TLBS_RANGE
>
> #define kvm_vm_is_protected(kvm) ((kvm)->arch.vm_flavor >= __VM_PROTECTED)
> +
> +#ifndef __KVM_NVHE_HYPERVISOR__
> #define vcpu_is_protected(vcpu) kvm_vm_is_protected((vcpu)->kvm)
> +#define vcpu_is_protected_pkvm(vcpu) kvm_vm_is_protected_pkvm((vcpu)->kvm)
> +#endif
>
> #define kvm_vm_is_protected_pkvm(kvm) \
> (is_protected_kvm_enabled() && ((kvm)->arch.vm_flavor == VM_PROTECTED_PKVM))
> -#define vcpu_is_protected_pkvm(vcpu) kvm_vm_is_protected_pkvm(vcpu->kvm)
>
> #define kvm_vm_is_unprotected_pkvm(kvm) \
> (is_protected_kvm_enabled() && ((kvm)->arch.vm_flavor == VM_PKVM))
> diff --git a/arch/arm64/include/asm/kvm_hyp.h b/arch/arm64/include/asm/kvm_hyp.h
> index 4974492744cc8..3bf87e81af430 100644
> --- a/arch/arm64/include/asm/kvm_hyp.h
> +++ b/arch/arm64/include/asm/kvm_hyp.h
> @@ -137,6 +137,19 @@ int __pkvm_init(phys_addr_t phys, unsigned long size, unsigned long *per_cpu_bas
> void __noreturn __host_enter(struct kvm_cpu_context *host_ctxt);
> #endif
>
> +#ifdef __KVM_NVHE_HYPERVISOR__
> +#define vcpu_is_protected(vcpu) \
> + ({ \
> + struct kvm *__kvm = READ_ONCE((vcpu)->kvm); \
> + __kvm && kvm_vm_is_protected((kern_hyp_va(__kvm))); \
> + })
> +#define vcpu_is_protected_pkvm(vcpu) \
> + ({ \
> + struct kvm *__kvm = READ_ONCE((vcpu)->kvm); \
> + __kvm && kvm_vm_is_protected_pkvm((kern_hyp_va(__kvm)));\
> + })
> +#endif
> +
>
>
> Or explicitly convert all nvhe accessors to a new "nvhe_vcpu_is_protected"
>
> The second one sounds like a better option to me.
>
We just need to include "asm/kvm_mmu.h" to "arch/arm64/mmio.c". With it,
we can have unified functions (macros) in kvm_host.h to accomodate all
cases, like below.
diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 9b1cf9c59e81..b9c9a9f203f9 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -1514,11 +1514,36 @@ struct kvm *kvm_arch_alloc_vm(void);
#define __KVM_HAVE_ARCH_FLUSH_REMOTE_TLBS_RANGE
#define kvm_vm_is_protected(kvm) ((kvm)->arch.vm_flavor >= __VM_PROTECTED)
-#define vcpu_is_protected(vcpu) kvm_vm_is_protected((vcpu)->kvm)
+#define vcpu_is_protected(vcpu) \
+ ({ \
+ struct kvm *__kvm = READ_ONCE((vcpu)->kvm); \
+ bool __protected = false; \
+ \
+ if (__kvm) { \
+ if (is_nvhe_hyp_code()) \
+ __kvm = kern_hyp_va(__kvm); \
+ __protected = kvm_vm_is_protected(__kvm); \
+ } \
+ \
+ __protected; \
+ })
+
#define kvm_vm_is_protected_pkvm(kvm) \
(is_protected_kvm_enabled() && ((kvm)->arch.vm_flavor == VM_PROTECTED_PKVM))
-#define vcpu_is_protected_pkvm(vcpu) kvm_vm_is_protected_pkvm(vcpu->kvm)
+#define vcpu_is_protected_pkvm(vcpu) \
+ ({ \
+ struct kvm *__kvm = READ_ONCE((vcpu)->kvm); \
+ bool __protected = false; \
+ \
+ if (__kvm) { \
+ if (is_nvhe_hyp_code()) \
+ __kvm = kern_hyp_va(__kvm); \
+ __protected = kvm_vm_is_protected_pkvm(__kvm); \
+ } \
+ \
+ __protected; \
+ })
#define kvm_vm_is_unprotected_pkvm(kvm) \
(is_protected_kvm_enabled() && ((kvm)->arch.vm_flavor == VM_PKVM))
diff --git a/arch/arm64/kvm/mmio.c b/arch/arm64/kvm/mmio.c
index d1c3a352d5a2..ab1d2fef9a52 100644
--- a/arch/arm64/kvm/mmio.c
+++ b/arch/arm64/kvm/mmio.c
@@ -6,6 +6,7 @@
#include <linux/kvm_host.h>
#include <asm/kvm_emulate.h>
+#include <asm/kvm_mmu.h>
#include <trace/events/kvm.h>
#include "trace.h"
Thanks,
Gavin
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