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[34.34.182.0]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-48fece998absm9721233f8f.22.2026.11.05.01.45.24 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 05 Nov 2026 01:45:24 -0800 (PST) Date: Thu, 5 Nov 2026 09:45:20 +0000 From: Vincent Donnefort To: Fuad Tabba Cc: Marc Zyngier , Oliver Upton , kvmarm@lists.linux.dev, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Joey Gouly , Steffen Eiden , Suzuki K Poulose , Zenghui Yu , Catalin Marinas , Will Deacon , Mark Rutland , Raghavendra Rao Ananta , Fuad Tabba Subject: Re: [PATCH v2 2/2] KVM: arm64: Resume a pKVM stage-2 teardown at the next mapping Message-ID: References: <20261104124451.2148724-1-fuad.tabba@linux.dev> <20261104124451.2148724-3-fuad.tabba@linux.dev> X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20261104124451.2148724-3-fuad.tabba@linux.dev> On Wed, Nov 04, 2026 at 12:44:51PM +0000, Fuad Tabba wrote: > pKVM keeps a VM's stage-2 mappings in an interval tree, and > pkvm_pgtable_stage2_destroy_range() releases the ones in its range. > stage2_destroy_range() still calls it for every block-sized chunk of the > IPA space. As pKVM gives every VM the host's IPA limit, a teardown with > LPA2 makes 2^27 calls with 16K pages (2^22 with 4K), however little the > VM maps. > > Return the address of the next mapping instead, or U64_MAX when none is > left, so that the teardown skips the space between mappings. No mapping > crosses a chunk boundary, as pKVM maps at most PMD_SIZE, so the next one > starts at or above the end of the range. A VM without a handle doesn't > have anything mapped, so return U64_MAX for it straight away. > > Signed-off-by: Fuad Tabba > --- > arch/arm64/kvm/pkvm.c | 8 ++++++-- > 1 file changed, 6 insertions(+), 2 deletions(-) > > diff --git a/arch/arm64/kvm/pkvm.c b/arch/arm64/kvm/pkvm.c > index f21c3326dda68..77315c83c61b3 100644 > --- a/arch/arm64/kvm/pkvm.c > +++ b/arch/arm64/kvm/pkvm.c > @@ -504,9 +504,10 @@ u64 pkvm_pgtable_stage2_destroy_range(struct kvm_pgtable *pgt, > { > struct kvm *kvm = kvm_s2_mmu_to_kvm(pgt->mmu); > pkvm_handle_t handle = kvm->arch.pkvm.handle; > + struct pkvm_mapping *mapping; > > if (!handle) > - return addr + size; > + return U64_MAX; > > if (pkvm_hyp_vm_is_created(kvm) && !kvm->arch.pkvm.is_dying) { > WARN_ON(kvm_call_hyp_nvhe(__pkvm_start_teardown_vm, handle)); > @@ -518,7 +519,10 @@ u64 pkvm_pgtable_stage2_destroy_range(struct kvm_pgtable *pgt, > else > __pkvm_pgtable_stage2_unshare(pgt, addr, addr + size); > > - return addr + size; > + /* Mappings left by a failed release are still in the tree, so look past the range. */ Hum, not sure I understand that comment. Which release are we talking about? The _reclaim or _unshare? If yes, we don't propagate the error and WARN if any of them fails. So we don't expect any failure here and I'd say there's nothing special to do? Additionally, in any case, iter_first(addr + size) seems like the right thing to do and is self-explanatory. > + mapping = pkvm_mapping_iter_first(&pgt->pkvm_mappings, addr + size, U64_MAX); > + > + return mapping ? gfn_to_gpa(mapping->gfn) : U64_MAX; > } > > void pkvm_pgtable_stage2_destroy_pgd(struct kvm_pgtable *pgt) > -- > 2.47.3 > Reviewed-by: Vincent Donnefort -- Vincent