* [PATCH] KVM: arm64: Fix debug checking for np-guests using huge mappings
@ 2025-08-15 16:26 Ben Horgan
2025-08-18 13:03 ` Vincent Donnefort
0 siblings, 1 reply; 2+ messages in thread
From: Ben Horgan @ 2025-08-15 16:26 UTC (permalink / raw)
To: catalin.marinas, will, maz, oliver.upton, joey.gouly,
suzuki.poulose, yuzenghui, linux-arm-kernel, kvmarm
Cc: james.morse, tabba, Ben Horgan, Vincent Donnefort, Quentin Perret,
Ryan Roberts, stable
When running with transparent huge pages and CONFIG_NVHE_EL2_DEBUG then
the debug checking in assert_host_shared_guest() fails on the launch of an
np-guest. This WARN_ON() causes a panic and generates the stack below.
In __pkvm_host_relax_perms_guest() the debug checking assumes the mapping
is a single page but it may be a block map. Update the checking so that
the size is not checked and just assumes the correct size.
While we're here make the same fix in __pkvm_host_mkyoung_guest().
Info: # lkvm run -k /share/arch/arm64/boot/Image -m 704 -c 8 --name guest-128
Info: Removed ghost socket file "/.lkvm//guest-128.sock".
[ 1406.521757] kvm [141]: nVHE hyp BUG at: arch/arm64/kvm/hyp/nvhe/mem_protect.c:1088!
[ 1406.521804] kvm [141]: nVHE call trace:
[ 1406.521828] kvm [141]: [<ffff8000811676b4>] __kvm_nvhe_hyp_panic+0xb4/0xe8
[ 1406.521946] kvm [141]: [<ffff80008116d12c>] __kvm_nvhe_assert_host_shared_guest+0xb0/0x10c
[ 1406.522049] kvm [141]: [<ffff80008116f068>] __kvm_nvhe___pkvm_host_relax_perms_guest+0x48/0x104
[ 1406.522157] kvm [141]: [<ffff800081169df8>] __kvm_nvhe_handle___pkvm_host_relax_perms_guest+0x64/0x7c
[ 1406.522250] kvm [141]: [<ffff800081169f0c>] __kvm_nvhe_handle_trap+0x8c/0x1a8
[ 1406.522333] kvm [141]: [<ffff8000811680fc>] __kvm_nvhe___skip_pauth_save+0x4/0x4
[ 1406.522454] kvm [141]: ---[ end nVHE call trace ]---
[ 1406.522477] kvm [141]: Hyp Offset: 0xfffece8013600000
[ 1406.522554] Kernel panic - not syncing: HYP panic:
[ 1406.522554] PS:834003c9 PC:0000b1806db6d170 ESR:00000000f2000800
[ 1406.522554] FAR:ffff8000804be420 HPFAR:0000000000804be0 PAR:0000000000000000
[ 1406.522554] VCPU:0000000000000000
[ 1406.523337] CPU: 3 UID: 0 PID: 141 Comm: kvm-vcpu-0 Not tainted 6.16.0-rc7 #97 PREEMPT
[ 1406.523485] Hardware name: FVP Base RevC (DT)
[ 1406.523566] Call trace:
[ 1406.523629] show_stack+0x18/0x24 (C)
[ 1406.523753] dump_stack_lvl+0xd4/0x108
[ 1406.523899] dump_stack+0x18/0x24
[ 1406.524040] panic+0x3d8/0x448
[ 1406.524184] nvhe_hyp_panic_handler+0x10c/0x23c
[ 1406.524325] kvm_handle_guest_abort+0x68c/0x109c
[ 1406.524500] handle_exit+0x60/0x17c
[ 1406.524630] kvm_arch_vcpu_ioctl_run+0x2e0/0x8c0
[ 1406.524794] kvm_vcpu_ioctl+0x1a8/0x9cc
[ 1406.524919] __arm64_sys_ioctl+0xac/0x104
[ 1406.525067] invoke_syscall+0x48/0x10c
[ 1406.525189] el0_svc_common.constprop.0+0x40/0xe0
[ 1406.525322] do_el0_svc+0x1c/0x28
[ 1406.525441] el0_svc+0x38/0x120
[ 1406.525588] el0t_64_sync_handler+0x10c/0x138
[ 1406.525750] el0t_64_sync+0x1ac/0x1b0
[ 1406.525876] SMP: stopping secondary CPUs
[ 1406.525965] Kernel Offset: disabled
[ 1406.526032] CPU features: 0x0000,00000080,8e134ca1,9446773f
[ 1406.526130] Memory Limit: none
[ 1406.959099] ---[ end Kernel panic - not syncing: HYP panic:
[ 1406.959099] PS:834003c9 PC:0000b1806db6d170 ESR:00000000f2000800
[ 1406.959099] FAR:ffff8000804be420 HPFAR:0000000000804be0 PAR:0000000000000000
[ 1406.959099] VCPU:0000000000000000 ]
Signed-off-by: Ben Horgan <ben.horgan@arm.com>
Fixes: db14091d8f75 ("KVM: arm64: Stage-2 huge mappings for np-guests")
Cc: Vincent Donnefort <vdonnefort@google.com>
Cc: Quentin Perret <qperret@google.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: stable@vger.kernel.org
---
This addresses the bug I raised here:
https://lore.kernel.org/linux-arm-kernel/17b526ff-b824-4c24-8ac0-6821e5cc8900@arm.com/
---
arch/arm64/kvm/hyp/nvhe/mem_protect.c | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)
diff --git a/arch/arm64/kvm/hyp/nvhe/mem_protect.c b/arch/arm64/kvm/hyp/nvhe/mem_protect.c
index 8957734d6183..ddc8beb55eee 100644
--- a/arch/arm64/kvm/hyp/nvhe/mem_protect.c
+++ b/arch/arm64/kvm/hyp/nvhe/mem_protect.c
@@ -1010,9 +1010,12 @@ static int __check_host_shared_guest(struct pkvm_hyp_vm *vm, u64 *__phys, u64 ip
return ret;
if (!kvm_pte_valid(pte))
return -ENOENT;
- if (kvm_granule_size(level) != size)
+ if (size && kvm_granule_size(level) != size)
return -E2BIG;
+ if (!size)
+ size = kvm_granule_size(level);
+
state = guest_get_page_state(pte, ipa);
if (state != PKVM_PAGE_SHARED_BORROWED)
return -EPERM;
@@ -1100,7 +1103,7 @@ int __pkvm_host_relax_perms_guest(u64 gfn, struct pkvm_hyp_vcpu *vcpu, enum kvm_
if (prot & ~KVM_PGTABLE_PROT_RWX)
return -EINVAL;
- assert_host_shared_guest(vm, ipa, PAGE_SIZE);
+ assert_host_shared_guest(vm, ipa, 0);
guest_lock_component(vm);
ret = kvm_pgtable_stage2_relax_perms(&vm->pgt, ipa, prot, 0);
guest_unlock_component(vm);
@@ -1156,7 +1159,7 @@ int __pkvm_host_mkyoung_guest(u64 gfn, struct pkvm_hyp_vcpu *vcpu)
if (pkvm_hyp_vm_is_protected(vm))
return -EPERM;
- assert_host_shared_guest(vm, ipa, PAGE_SIZE);
+ assert_host_shared_guest(vm, ipa, 0);
guest_lock_component(vm);
kvm_pgtable_stage2_mkyoung(&vm->pgt, ipa, 0);
guest_unlock_component(vm);
--
2.43.0
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH] KVM: arm64: Fix debug checking for np-guests using huge mappings
2025-08-15 16:26 [PATCH] KVM: arm64: Fix debug checking for np-guests using huge mappings Ben Horgan
@ 2025-08-18 13:03 ` Vincent Donnefort
0 siblings, 0 replies; 2+ messages in thread
From: Vincent Donnefort @ 2025-08-18 13:03 UTC (permalink / raw)
To: Ben Horgan
Cc: catalin.marinas, will, maz, oliver.upton, joey.gouly,
suzuki.poulose, yuzenghui, linux-arm-kernel, kvmarm, james.morse,
tabba, Quentin Perret, Ryan Roberts, stable
Thanks for the fix!
On Fri, Aug 15, 2025 at 05:26:55PM +0100, Ben Horgan wrote:
> When running with transparent huge pages and CONFIG_NVHE_EL2_DEBUG then
> the debug checking in assert_host_shared_guest() fails on the launch of an
> np-guest. This WARN_ON() causes a panic and generates the stack below.
>
> In __pkvm_host_relax_perms_guest() the debug checking assumes the mapping
> is a single page but it may be a block map. Update the checking so that
> the size is not checked and just assumes the correct size.
>
> While we're here make the same fix in __pkvm_host_mkyoung_guest().
>
> Info: # lkvm run -k /share/arch/arm64/boot/Image -m 704 -c 8 --name guest-128
> Info: Removed ghost socket file "/.lkvm//guest-128.sock".
> [ 1406.521757] kvm [141]: nVHE hyp BUG at: arch/arm64/kvm/hyp/nvhe/mem_protect.c:1088!
> [ 1406.521804] kvm [141]: nVHE call trace:
> [ 1406.521828] kvm [141]: [<ffff8000811676b4>] __kvm_nvhe_hyp_panic+0xb4/0xe8
> [ 1406.521946] kvm [141]: [<ffff80008116d12c>] __kvm_nvhe_assert_host_shared_guest+0xb0/0x10c
> [ 1406.522049] kvm [141]: [<ffff80008116f068>] __kvm_nvhe___pkvm_host_relax_perms_guest+0x48/0x104
> [ 1406.522157] kvm [141]: [<ffff800081169df8>] __kvm_nvhe_handle___pkvm_host_relax_perms_guest+0x64/0x7c
> [ 1406.522250] kvm [141]: [<ffff800081169f0c>] __kvm_nvhe_handle_trap+0x8c/0x1a8
> [ 1406.522333] kvm [141]: [<ffff8000811680fc>] __kvm_nvhe___skip_pauth_save+0x4/0x4
> [ 1406.522454] kvm [141]: ---[ end nVHE call trace ]---
> [ 1406.522477] kvm [141]: Hyp Offset: 0xfffece8013600000
> [ 1406.522554] Kernel panic - not syncing: HYP panic:
> [ 1406.522554] PS:834003c9 PC:0000b1806db6d170 ESR:00000000f2000800
> [ 1406.522554] FAR:ffff8000804be420 HPFAR:0000000000804be0 PAR:0000000000000000
> [ 1406.522554] VCPU:0000000000000000
> [ 1406.523337] CPU: 3 UID: 0 PID: 141 Comm: kvm-vcpu-0 Not tainted 6.16.0-rc7 #97 PREEMPT
> [ 1406.523485] Hardware name: FVP Base RevC (DT)
> [ 1406.523566] Call trace:
> [ 1406.523629] show_stack+0x18/0x24 (C)
> [ 1406.523753] dump_stack_lvl+0xd4/0x108
> [ 1406.523899] dump_stack+0x18/0x24
> [ 1406.524040] panic+0x3d8/0x448
> [ 1406.524184] nvhe_hyp_panic_handler+0x10c/0x23c
> [ 1406.524325] kvm_handle_guest_abort+0x68c/0x109c
> [ 1406.524500] handle_exit+0x60/0x17c
> [ 1406.524630] kvm_arch_vcpu_ioctl_run+0x2e0/0x8c0
> [ 1406.524794] kvm_vcpu_ioctl+0x1a8/0x9cc
> [ 1406.524919] __arm64_sys_ioctl+0xac/0x104
> [ 1406.525067] invoke_syscall+0x48/0x10c
> [ 1406.525189] el0_svc_common.constprop.0+0x40/0xe0
> [ 1406.525322] do_el0_svc+0x1c/0x28
> [ 1406.525441] el0_svc+0x38/0x120
> [ 1406.525588] el0t_64_sync_handler+0x10c/0x138
> [ 1406.525750] el0t_64_sync+0x1ac/0x1b0
> [ 1406.525876] SMP: stopping secondary CPUs
> [ 1406.525965] Kernel Offset: disabled
> [ 1406.526032] CPU features: 0x0000,00000080,8e134ca1,9446773f
> [ 1406.526130] Memory Limit: none
> [ 1406.959099] ---[ end Kernel panic - not syncing: HYP panic:
> [ 1406.959099] PS:834003c9 PC:0000b1806db6d170 ESR:00000000f2000800
> [ 1406.959099] FAR:ffff8000804be420 HPFAR:0000000000804be0 PAR:0000000000000000
> [ 1406.959099] VCPU:0000000000000000 ]
>
> Signed-off-by: Ben Horgan <ben.horgan@arm.com>
> Fixes: db14091d8f75 ("KVM: arm64: Stage-2 huge mappings for np-guests")
Not sure if it really matters but it's more about fixing f28f1d02f4ea (KVM: arm64: Add a range
to __pkvm_host_unshare_guest()) which introduced the check size !=
kvm_granule_size(). Even though this is noop until db14091d8f75
> Cc: Vincent Donnefort <vdonnefort@google.com>
> Cc: Quentin Perret <qperret@google.com>
> Cc: Ryan Roberts <ryan.roberts@arm.com>
> Cc: stable@vger.kernel.org
Reviewed-by: Vincent Donnefort <vdonnefort@google.com>
>
> ---
>
> This addresses the bug I raised here:
> https://lore.kernel.org/linux-arm-kernel/17b526ff-b824-4c24-8ac0-6821e5cc8900@arm.com/
>
> ---
> arch/arm64/kvm/hyp/nvhe/mem_protect.c | 9 ++++++---
> 1 file changed, 6 insertions(+), 3 deletions(-)
>
> diff --git a/arch/arm64/kvm/hyp/nvhe/mem_protect.c b/arch/arm64/kvm/hyp/nvhe/mem_protect.c
> index 8957734d6183..ddc8beb55eee 100644
> --- a/arch/arm64/kvm/hyp/nvhe/mem_protect.c
> +++ b/arch/arm64/kvm/hyp/nvhe/mem_protect.c
> @@ -1010,9 +1010,12 @@ static int __check_host_shared_guest(struct pkvm_hyp_vm *vm, u64 *__phys, u64 ip
> return ret;
> if (!kvm_pte_valid(pte))
> return -ENOENT;
> - if (kvm_granule_size(level) != size)
> + if (size && kvm_granule_size(level) != size)
> return -E2BIG;
>
> + if (!size)
> + size = kvm_granule_size(level);
> +
> state = guest_get_page_state(pte, ipa);
> if (state != PKVM_PAGE_SHARED_BORROWED)
> return -EPERM;
> @@ -1100,7 +1103,7 @@ int __pkvm_host_relax_perms_guest(u64 gfn, struct pkvm_hyp_vcpu *vcpu, enum kvm_
> if (prot & ~KVM_PGTABLE_PROT_RWX)
> return -EINVAL;
>
> - assert_host_shared_guest(vm, ipa, PAGE_SIZE);
> + assert_host_shared_guest(vm, ipa, 0);
> guest_lock_component(vm);
> ret = kvm_pgtable_stage2_relax_perms(&vm->pgt, ipa, prot, 0);
> guest_unlock_component(vm);
> @@ -1156,7 +1159,7 @@ int __pkvm_host_mkyoung_guest(u64 gfn, struct pkvm_hyp_vcpu *vcpu)
> if (pkvm_hyp_vm_is_protected(vm))
> return -EPERM;
>
> - assert_host_shared_guest(vm, ipa, PAGE_SIZE);
> + assert_host_shared_guest(vm, ipa, 0);
> guest_lock_component(vm);
> kvm_pgtable_stage2_mkyoung(&vm->pgt, ipa, 0);
> guest_unlock_component(vm);
> --
> 2.43.0
>
^ permalink raw reply [flat|nested] 2+ messages in thread
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