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-b824-4c24-8ac0-6821e5cc890...
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