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[2003:d8:2f1d:ed00:1769:dd7c:7208:eb33]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4562e8027f9sm17107415e9.14.2025.07.16.03.36.44 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 16 Jul 2025 03:36:46 -0700 (PDT) Message-ID: <39a217c1-29a9-4497-b3b6-bc0459e75a91@redhat.com> Date: Wed, 16 Jul 2025 12:36:43 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v14 15/21] KVM: arm64: Refactor user_mem_abort() To: Fuad Tabba , kvm@vger.kernel.org, linux-arm-msm@vger.kernel.org, linux-mm@kvack.org, kvmarm@lists.linux.dev Cc: pbonzini@redhat.com, chenhuacai@kernel.org, mpe@ellerman.id.au, anup@brainfault.org, paul.walmsley@sifive.com, palmer@dabbelt.com, aou@eecs.berkeley.edu, seanjc@google.com, viro@zeniv.linux.org.uk, brauner@kernel.org, willy@infradead.org, akpm@linux-foundation.org, xiaoyao.li@intel.com, yilun.xu@intel.com, chao.p.peng@linux.intel.com, jarkko@kernel.org, amoorthy@google.com, dmatlack@google.com, isaku.yamahata@intel.com, mic@digikod.net, vbabka@suse.cz, vannapurve@google.com, ackerleytng@google.com, mail@maciej.szmigiero.name, michael.roth@amd.com, wei.w.wang@intel.com, liam.merwick@oracle.com, isaku.yamahata@gmail.com, kirill.shutemov@linux.intel.com, suzuki.poulose@arm.com, steven.price@arm.com, quic_eberman@quicinc.com, quic_mnalajal@quicinc.com, quic_tsoni@quicinc.com, quic_svaddagi@quicinc.com, quic_cvanscha@quicinc.com, quic_pderrin@quicinc.com, quic_pheragu@quicinc.com, catalin.marinas@arm.com, james.morse@arm.com, yuzenghui@huawei.com, oliver.upton@linux.dev, maz@kernel.org, will@kernel.org, qperret@google.com, keirf@google.com, roypat@amazon.co.uk, shuah@kernel.org, hch@infradead.org, jgg@nvidia.com, rientjes@google.com, jhubbard@nvidia.com, fvdl@google.com, hughd@google.com, jthoughton@google.com, peterx@redhat.com, pankaj.gupta@amd.com, ira.weiny@intel.com References: <20250715093350.2584932-1-tabba@google.com> <20250715093350.2584932-16-tabba@google.com> From: David Hildenbrand Autocrypt: addr=david@redhat.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 98BF418000A X-Stat-Signature: imfmfm1nf6pt1fdjp4gzrdxkhxfrtzzp X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1752662211-218969 X-HE-Meta: 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 lQhoXVO6 HndTvna8aDJ6KN6OQcVuXevRXv+3FDxLZH5kYmWrZ5iv7ZWP+R3ctiTYMMGvUkQUpsqO4M/xTiFV0TmBAHdYPhCBBaze/5PckE2lKeZxJYDsdk6r31YjMrGr/orziOvBAZMy85f8M2PGlq/Xg1xXXJUPeSJARxSDn2h2yaixd+Jj5aUMo8hiuGT9fN23rRiwiVqIQWr7zP3Yp8RM4lFAxTt7VixW0+Z4acz3fb6x5RHtH/Vs6lIPboVTseaq7vu86lGQNhjaUHn/Z444dXV4Nh/5kM6lRhmFSfHSqKn1CTw9VvucHz5H3R57cLIXwMMDHbaSONSPtIkLVzXLf7vxQkav0gwump7JNvvGHAhIcjY7hvfe8S0xce+fZ7hSRWd92hmhUiTZmoxUJxJzJoPkQbgJ4xHk74eh8CGnS8g+s3UzpGjozMdhzQIJ+UmNalp7mFyl+hbR88Bh11JoO7BoQ0UoqCEHzwRzU/DDo9L4q0S0pKTXs2n5qMbsrNrm84WofolsiPSiFmV0KXJBfF77ru3UzEF3Kz2I1FltXWjZ8SpuzaFcOVYl3PrJqigWs1N9Otue3xXM6+kjrhoxbewTTvFpsiaH/a1uTXm3Rn4lQxqSroY4= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 15.07.25 11:33, Fuad Tabba wrote: > Refactor user_mem_abort() to improve code clarity and simplify > assumptions within the function. > > Key changes include: > > * Immediately set force_pte to true at the beginning of the function if > logging_active is true. This simplifies the flow and makes the > condition for forcing a PTE more explicit. > > * Remove the misleading comment stating that logging_active is > guaranteed to never be true for VM_PFNMAP memslots, as this assertion > is not entirely correct. > > * Extract reusable code blocks into new helper functions: > * prepare_mmu_memcache(): Encapsulates the logic for preparing and > topping up the MMU page cache. > * adjust_nested_fault_perms(): Isolates the adjustments to shadow S2 > permissions and the encoding of nested translation levels. > > * Update min(a, (long)b) to min_t(long, a, b) for better type safety and > consistency. > > * Perform other minor tidying up of the code. > > These changes primarily aim to simplify user_mem_abort() and make its > logic easier to understand and maintain, setting the stage for future > modifications. > > Reviewed-by: Gavin Shan > Reviewed-by: Marc Zyngier > Signed-off-by: Fuad Tabba > --- > arch/arm64/kvm/mmu.c | 110 +++++++++++++++++++++++-------------------- > 1 file changed, 59 insertions(+), 51 deletions(-) > > diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c > index 2942ec92c5a4..b3eacb400fab 100644 > --- a/arch/arm64/kvm/mmu.c > +++ b/arch/arm64/kvm/mmu.c > @@ -1470,13 +1470,56 @@ static bool kvm_vma_mte_allowed(struct vm_area_struct *vma) > return vma->vm_flags & VM_MTE_ALLOWED; > } > > +static int prepare_mmu_memcache(struct kvm_vcpu *vcpu, bool topup_memcache, > + void **memcache) > +{ > + int min_pages; > + > + if (!is_protected_kvm_enabled()) > + *memcache = &vcpu->arch.mmu_page_cache; > + else > + *memcache = &vcpu->arch.pkvm_memcache; > + > + if (!topup_memcache) > + return 0; > + > + min_pages = kvm_mmu_cache_min_pages(vcpu->arch.hw_mmu); > + > + if (!is_protected_kvm_enabled()) > + return kvm_mmu_topup_memory_cache(*memcache, min_pages); > + > + return topup_hyp_memcache(*memcache, min_pages); > +} > + > +/* > + * Potentially reduce shadow S2 permissions to match the guest's own S2. For > + * exec faults, we'd only reach this point if the guest actually allowed it (see > + * kvm_s2_handle_perm_fault). > + * > + * Also encode the level of the original translation in the SW bits of the leaf > + * entry as a proxy for the span of that translation. This will be retrieved on > + * TLB invalidation from the guest and used to limit the invalidation scope if a > + * TTL hint or a range isn't provided. > + */ > +static void adjust_nested_fault_perms(struct kvm_s2_trans *nested, > + enum kvm_pgtable_prot *prot, > + bool *writable) > +{ > + *writable &= kvm_s2_trans_writable(nested); > + if (!kvm_s2_trans_readable(nested)) > + *prot &= ~KVM_PGTABLE_PROT_R; > + > + *prot |= kvm_encode_nested_level(nested); > +} > + > static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa, > struct kvm_s2_trans *nested, > struct kvm_memory_slot *memslot, unsigned long hva, > bool fault_is_perm) > { > int ret = 0; > - bool write_fault, writable, force_pte = false; > + bool topup_memcache; > + bool write_fault, writable; > bool exec_fault, mte_allowed; > bool device = false, vfio_allow_any_uc = false; > unsigned long mmu_seq; > @@ -1488,6 +1531,7 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa, > gfn_t gfn; > kvm_pfn_t pfn; > bool logging_active = memslot_is_logging(memslot); > + bool force_pte = logging_active; > long vma_pagesize, fault_granule; > enum kvm_pgtable_prot prot = KVM_PGTABLE_PROT_R; > struct kvm_pgtable *pgt; > @@ -1498,17 +1542,7 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa, > fault_granule = kvm_vcpu_trap_get_perm_fault_granule(vcpu); > write_fault = kvm_is_write_fault(vcpu); > exec_fault = kvm_vcpu_trap_is_exec_fault(vcpu); > - VM_BUG_ON(write_fault && exec_fault); > - > - if (fault_is_perm && !write_fault && !exec_fault) { > - kvm_err("Unexpected L2 read permission error\n"); > - return -EFAULT; > - } > - > - if (!is_protected_kvm_enabled()) > - memcache = &vcpu->arch.mmu_page_cache; > - else > - memcache = &vcpu->arch.pkvm_memcache; > + VM_WARN_ON_ONCE(write_fault && exec_fault); > > /* > * Permission faults just need to update the existing leaf entry, > @@ -1516,17 +1550,10 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa, > * only exception to this is when dirty logging is enabled at runtime > * and a write fault needs to collapse a block entry into a table. > */ > - if (!fault_is_perm || (logging_active && write_fault)) { > - int min_pages = kvm_mmu_cache_min_pages(vcpu->arch.hw_mmu); > - > - if (!is_protected_kvm_enabled()) > - ret = kvm_mmu_topup_memory_cache(memcache, min_pages); > - else > - ret = topup_hyp_memcache(memcache, min_pages); > - > - if (ret) > - return ret; > - } > + topup_memcache = !fault_is_perm || (logging_active && write_fault); > + ret = prepare_mmu_memcache(vcpu, topup_memcache, &memcache); > + if (ret) > + return ret; > > /* > * Let's check if we will get back a huge page backed by hugetlbfs, or > @@ -1540,16 +1567,10 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa, > return -EFAULT; > } > > - /* > - * logging_active is guaranteed to never be true for VM_PFNMAP > - * memslots. > - */ > - if (logging_active) { > - force_pte = true; > + if (force_pte) > vma_shift = PAGE_SHIFT; > - } else { > + else > vma_shift = get_vma_page_shift(vma, hva); > - } > > switch (vma_shift) { > #ifndef __PAGETABLE_PMD_FOLDED > @@ -1601,7 +1622,7 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa, > max_map_size = PAGE_SIZE; > > force_pte = (max_map_size == PAGE_SIZE); > - vma_pagesize = min(vma_pagesize, (long)max_map_size); > + vma_pagesize = min_t(long, vma_pagesize, max_map_size); > } > > /* > @@ -1630,7 +1651,7 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa, > * Rely on mmap_read_unlock() for an implicit smp_rmb(), which pairs > * with the smp_wmb() in kvm_mmu_invalidate_end(). > */ > - mmu_seq = vcpu->kvm->mmu_invalidate_seq; > + mmu_seq = kvm->mmu_invalidate_seq; > mmap_read_unlock(current->mm); > > pfn = __kvm_faultin_pfn(memslot, gfn, write_fault ? FOLL_WRITE : 0, > @@ -1665,24 +1686,8 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa, > if (exec_fault && device) > return -ENOEXEC; > > - /* > - * Potentially reduce shadow S2 permissions to match the guest's own > - * S2. For exec faults, we'd only reach this point if the guest > - * actually allowed it (see kvm_s2_handle_perm_fault). > - * > - * Also encode the level of the original translation in the SW bits > - * of the leaf entry as a proxy for the span of that translation. > - * This will be retrieved on TLB invalidation from the guest and > - * used to limit the invalidation scope if a TTL hint or a range > - * isn't provided. > - */ > - if (nested) { > - writable &= kvm_s2_trans_writable(nested); > - if (!kvm_s2_trans_readable(nested)) > - prot &= ~KVM_PGTABLE_PROT_R; > - > - prot |= kvm_encode_nested_level(nested); > - } > + if (nested) > + adjust_nested_fault_perms(nested, &prot, &writable); > > kvm_fault_lock(kvm); > pgt = vcpu->arch.hw_mmu->pgt; > @@ -1953,6 +1958,9 @@ int kvm_handle_guest_abort(struct kvm_vcpu *vcpu) > goto out_unlock; > } > > + VM_WARN_ON_ONCE(kvm_vcpu_trap_is_permission_fault(vcpu) && > + !write_fault && !kvm_vcpu_trap_is_exec_fault(vcpu)); > + > ret = user_mem_abort(vcpu, fault_ipa, nested, memslot, hva, > esr_fsc_is_permission_fault(esr)); > if (ret == 0) A note that on the KVM arm next tree https://git.kernel.org/pub/scm/linux/kernel/git/kvmarm/kvmarm.git/log/?h=next there are some user_mem_abort() changes. IIUC, only smaller conflicts. -- Cheers, David / dhildenb