[PATCH v19 05/20] KVM: arm64: Track the type of VM in kvm_arch
Suzuki K Poulose
suzuki.poulose at arm.com
Wed Sep 23 14:37:03 PDT 2026
On 23/09/2026 17:27, Suzuki K Poulose wrote:
> On 23/09/2026 14:23, Gavin Shan wrote:
>> 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()) \
This needs to be :
if (is_nvhe_hyp_code() && !is_protected_kvm_enabled())
>> + __kvm = kern_hyp_va(__kvm); \
Otherwise, we unnecessarily convert the vcpu->kvm for a hyp_vcpu and
that is not going to end well for pKVM.
Cheers
Suzuki
>> + __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, that works and looks neat. I will incorporate it.
>
> Cheers
> Suzuki
>
>> Thanks,
>> Gavin
>>
>
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