[PATCH v19 05/20] KVM: arm64: Track the type of VM in kvm_arch
Suzuki K Poulose
suzuki.poulose at arm.com
Thu Sep 24 01:48:14 PDT 2026
On 24/09/2026 02:11, Gavin Shan wrote:
> On 9/24/26 7:37 AM, Suzuki K Poulose wrote:
>> 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())
>>
>
> Yes.
>
>>>> + __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.
>>
>
> Yes. kern_hyp_va() isn't needed when is_protected_kvm_enabled() is true.
nit : It is not that it is needed, but it is incorrect to convert the
vcpu->kvm which is already a HYP VA via kern_hyp_va() which is not
idempotent and thus we end up accessing something junk.
> Besides, vcpu_is_protected_pkvm() can be further simplifed by fully
> exploiting
> the check (is_protected_kvm_enabled()) done in vcpu_is_protected_pkvm(),
> see below.
Good point.
>
>> 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; \
>>>> + })
>
> This can be further simplified by fully expliting the check
> (is_protected_kvm_enabled())
> in kvm_vm_is_protected_pkvm(), as below. The point is that the check
> is_protected_kvm_enabled()
> gurantees that kern_hyp_va() isn't needed.
>
> #define vcpu_is_protected_pkvm(vcpu) \
> ({ \
> struct kvm *__kvm = READ_ONCE((vcpu)->kvm); \
> bool __protected = false; \
> \
> if (__kvm) \
> __protected = kvm_vm_is_protected_pkvm(__kvm); \
> \
> __protected; \
> })
>
Ack, I have reduced this to:
/*
* Rely on is_protected_kvm_enabled() check in
kvm_vm_is_protected_pkvm() to
* make sure the vcpu->kvm is always valid VA in the context
*/
#define vcpu_is_protected_pkvm(vcpu) \
({ \
struct kvm *__kvm = READ_ONCE((vcpu)->kvm); \
\
(__kvm) && kvm_vm_is_protected_pkvm(__kvm)); \
})
Cheers
Suzuki
>>>>
>>>> #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.
>>>
>
> Thanks,
> Gavin
>
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