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[35.195.29.211]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-afcdcfcce69sm785410866b.82.2025.08.18.06.04.00 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 18 Aug 2025 06:04:01 -0700 (PDT) Date: Mon, 18 Aug 2025 14:03:57 +0100 From: Vincent Donnefort To: Ben Horgan Cc: catalin.marinas@arm.com, will@kernel.org, maz@kernel.org, oliver.upton@linux.dev, joey.gouly@arm.com, suzuki.poulose@arm.com, yuzenghui@huawei.com, linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, james.morse@arm.com, tabba@google.com, Quentin Perret , Ryan Roberts , stable@vger.kernel.org Subject: Re: [PATCH] KVM: arm64: Fix debug checking for np-guests using huge mappings Message-ID: References: <20250815162655.121108-1-ben.horgan@arm.com> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250815162655.121108-1-ben.horgan@arm.com> 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]: [] __kvm_nvhe_hyp_panic+0xb4/0xe8 > [ 1406.521946] kvm [141]: [] __kvm_nvhe_assert_host_shared_guest+0xb0/0x10c > [ 1406.522049] kvm [141]: [] __kvm_nvhe___pkvm_host_relax_perms_guest+0x48/0x104 > [ 1406.522157] kvm [141]: [] __kvm_nvhe_handle___pkvm_host_relax_perms_guest+0x64/0x7c > [ 1406.522250] kvm [141]: [] __kvm_nvhe_handle_trap+0x8c/0x1a8 > [ 1406.522333] kvm [141]: [] __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 > 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 > Cc: Quentin Perret > Cc: Ryan Roberts > Cc: stable@vger.kernel.org Reviewed-by: Vincent Donnefort > > --- > > 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 >