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charset="utf-8" Avoid a NULL pointer dereference if the memslot table changes between the exit and the call to kvmppc_e500_shadow_map(). Cc: stable@vger.kernel.org Signed-off-by: Paolo Bonzini --- arch/powerpc/kvm/e500_mmu_host.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/arch/powerpc/kvm/e500_mmu_host.c b/arch/powerpc/kvm/e500_mmu_h= ost.c index e5a145b578a4..732335444d68 100644 --- a/arch/powerpc/kvm/e500_mmu_host.c +++ b/arch/powerpc/kvm/e500_mmu_host.c @@ -349,6 +349,11 @@ static inline int kvmppc_e500_shadow_map(struct kvmppc= _vcpu_e500 *vcpu_e500, * pointer through from the first lookup. */ slot =3D gfn_to_memslot(vcpu_e500->vcpu.kvm, gfn); + if (!slot) { + ret =3D -EAGAIN; + goto out; + } + hva =3D gfn_to_hva_memslot(slot, gfn); =20 if (tlbsel =3D=3D 1) { --=20 2.47.1 From nobody Sat Feb 7 06:28:11 2026 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id DBA9E2206B6 for ; Thu, 9 Jan 2025 13:38:29 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; 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charset="utf-8" kvmppc_e500_ref_setup is returning whether the guest TLB entry is writable, which is than passed to kvm_release_faultin_page. This makes little sense for two reasons: first, because the function sets up the private data for the page and the return value feels like it has been bolted on the side; second, because what really matters is whether the _shadow_ TLB entry is writable. If it is not writable, the page can be released as non-dirty. Shift from using tlbe_is_writable(gtlbe) to doing the same check on the shadow TLB entry. Signed-off-by: Paolo Bonzini --- arch/powerpc/kvm/e500_mmu_host.c | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-) diff --git a/arch/powerpc/kvm/e500_mmu_host.c b/arch/powerpc/kvm/e500_mmu_h= ost.c index 732335444d68..06e23c625be0 100644 --- a/arch/powerpc/kvm/e500_mmu_host.c +++ b/arch/powerpc/kvm/e500_mmu_host.c @@ -242,7 +242,7 @@ static inline int tlbe_is_writable(struct kvm_book3e_20= 6_tlb_entry *tlbe) return tlbe->mas7_3 & (MAS3_SW|MAS3_UW); } =20 -static inline bool kvmppc_e500_ref_setup(struct tlbe_ref *ref, +static inline void kvmppc_e500_ref_setup(struct tlbe_ref *ref, struct kvm_book3e_206_tlb_entry *gtlbe, kvm_pfn_t pfn, unsigned int wimg) { @@ -251,8 +251,6 @@ static inline bool kvmppc_e500_ref_setup(struct tlbe_re= f *ref, =20 /* Use guest supplied MAS2_G and MAS2_E */ ref->flags |=3D (gtlbe->mas2 & MAS2_ATTRIB_MASK) | wimg; - - return tlbe_is_writable(gtlbe); } =20 static inline void kvmppc_e500_ref_release(struct tlbe_ref *ref) @@ -493,10 +491,11 @@ static inline int kvmppc_e500_shadow_map(struct kvmpp= c_vcpu_e500 *vcpu_e500, goto out; 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charset="utf-8" Add the possibility of marking a page so that the UW and SW bits are force-cleared. This is stored in the private info so that it persists across multiple calls to kvmppc_e500_setup_stlbe. Signed-off-by: Paolo Bonzini --- arch/powerpc/kvm/e500.h | 2 ++ arch/powerpc/kvm/e500_mmu_host.c | 15 +++++++++++---- 2 files changed, 13 insertions(+), 4 deletions(-) diff --git a/arch/powerpc/kvm/e500.h b/arch/powerpc/kvm/e500.h index 6d0d329cbb35..f9acf866c709 100644 --- a/arch/powerpc/kvm/e500.h +++ b/arch/powerpc/kvm/e500.h @@ -34,6 +34,8 @@ enum vcpu_ftr { #define E500_TLB_BITMAP (1 << 30) /* TLB1 entry is mapped by host TLB0 */ #define E500_TLB_TLB0 (1 << 29) +/* entry is writable on the host */ +#define E500_TLB_WRITABLE (1 << 28) /* bits [6-5] MAS2_X1 and MAS2_X0 and [4-0] bits for WIMGE */ #define E500_TLB_MAS2_ATTR (0x7f) =20 diff --git a/arch/powerpc/kvm/e500_mmu_host.c b/arch/powerpc/kvm/e500_mmu_h= ost.c index 06e23c625be0..e332a10fff00 100644 --- a/arch/powerpc/kvm/e500_mmu_host.c +++ b/arch/powerpc/kvm/e500_mmu_host.c @@ -45,11 +45,14 @@ static inline unsigned int tlb1_max_shadow_size(void) return host_tlb_params[1].entries - tlbcam_index - 1; } =20 -static inline u32 e500_shadow_mas3_attrib(u32 mas3, int usermode) +static inline u32 e500_shadow_mas3_attrib(u32 mas3, bool writable, int use= rmode) { /* Mask off reserved bits. */ mas3 &=3D MAS3_ATTRIB_MASK; =20 + if (!writable) + mas3 &=3D ~(MAS3_UW|MAS3_SW); + #ifndef CONFIG_KVM_BOOKE_HV if (!usermode) { /* Guest is in supervisor mode, @@ -244,10 +247,13 @@ static inline int tlbe_is_writable(struct kvm_book3e_= 206_tlb_entry *tlbe) =20 static inline void kvmppc_e500_ref_setup(struct tlbe_ref *ref, struct kvm_book3e_206_tlb_entry *gtlbe, - kvm_pfn_t pfn, unsigned int wimg) + kvm_pfn_t pfn, unsigned int wimg, + bool writable) { ref->pfn =3D pfn; ref->flags =3D E500_TLB_VALID; + if (writable) + ref->flags |=3D E500_TLB_WRITABLE; =20 /* Use guest supplied MAS2_G and MAS2_E */ ref->flags |=3D (gtlbe->mas2 & MAS2_ATTRIB_MASK) | wimg; @@ -303,6 +309,7 @@ static void kvmppc_e500_setup_stlbe( { kvm_pfn_t pfn =3D ref->pfn; u32 pr =3D vcpu->arch.shared->msr & MSR_PR; + bool writable =3D !!(ref->flags & E500_TLB_WRITABLE); =20 BUG_ON(!(ref->flags & E500_TLB_VALID)); =20 @@ -310,7 +317,7 @@ static void kvmppc_e500_setup_stlbe( stlbe->mas1 =3D MAS1_TSIZE(tsize) | get_tlb_sts(gtlbe) | MAS1_VALID; stlbe->mas2 =3D (gvaddr & MAS2_EPN) | (ref->flags & E500_TLB_MAS2_ATTR); 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charset="utf-8" The new __kvm_faultin_pfn() function is upset by the fact that e500 KVM ignores host page permissions - __kvm_faultin requires a "writable" outgoing argument, but e500 KVM is nonchalantly passing NULL. If the host page permissions do not include writability, the shadow TLB entry is forcibly mapped read-only. Reported-by: Christian Zigotzky Signed-off-by: Paolo Bonzini --- arch/powerpc/kvm/e500_mmu_host.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/arch/powerpc/kvm/e500_mmu_host.c b/arch/powerpc/kvm/e500_mmu_h= ost.c index e332a10fff00..7752b7f24c51 100644 --- a/arch/powerpc/kvm/e500_mmu_host.c +++ b/arch/powerpc/kvm/e500_mmu_host.c @@ -379,6 +379,7 @@ static inline int kvmppc_e500_shadow_map(struct kvmppc_= vcpu_e500 *vcpu_e500, unsigned long slot_start, slot_end; =20 pfnmap =3D 1; + writable =3D vma->vm_flags & VM_WRITE; =20 start =3D vma->vm_pgoff; end =3D start + @@ -454,7 +455,7 @@ static inline int kvmppc_e500_shadow_map(struct kvmppc_= vcpu_e500 *vcpu_e500, =20 if (likely(!pfnmap)) { tsize_pages =3D 1UL << (tsize + 10 - PAGE_SHIFT); - pfn =3D __kvm_faultin_pfn(slot, gfn, FOLL_WRITE, NULL, &page); + pfn =3D __kvm_faultin_pfn(slot, gfn, FOLL_WRITE, &writable, &page); if (is_error_noslot_pfn(pfn)) { if (printk_ratelimit()) pr_err("%s: real page not found for gfn %lx\n", @@ -499,7 +500,7 @@ static inline int kvmppc_e500_shadow_map(struct kvmppc_= vcpu_e500 *vcpu_e500, } } =20 - kvmppc_e500_ref_setup(ref, gtlbe, pfn, wimg, true); 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Thu, 09 Jan 2025 05:38:33 -0800 (PST) X-Google-Smtp-Source: AGHT+IEvrvZyCjR9P8H1XfDQSbpZ1ii019x3nOmgFJfPU4BSjpH27IgNbkbMhVv45gD16B6Iwt+Skw== X-Received: by 2002:a05:6402:5251:b0:5d0:bf5e:eb8 with SMTP id 4fb4d7f45d1cf-5d972e63ddfmr13854906a12.23.1736429912705; Thu, 09 Jan 2025 05:38:32 -0800 (PST) Received: from [192.168.10.47] ([151.62.105.73]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-ab2c90d6a4csm73856966b.71.2025.01.09.05.38.31 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 09 Jan 2025 05:38:32 -0800 (PST) From: Paolo Bonzini To: linux-kernel@vger.kernel.org, kvm@vger.kernel.org Cc: oliver.upton@linux.dev, Will Deacon , Anup Patel , Andrew Jones , seanjc@google.com, linuxppc-dev@lists.ozlabs.org, regressions@lists.linux.dev Subject: [PATCH 5/5] KVM: e500: perform hugepage check after looking up the PFN Date: Thu, 9 Jan 2025 14:38:17 +0100 Message-ID: <20250109133817.314401-6-pbonzini@redhat.com> X-Mailer: git-send-email 2.47.1 In-Reply-To: <20250109133817.314401-1-pbonzini@redhat.com> References: <20250109133817.314401-1-pbonzini@redhat.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" e500 KVM tries to bypass __kvm_faultin_pfn() in order to map VM_PFNMAP VMAs as huge pages. This is a Bad Idea because VM_PFNMAP VMAs could become noncontiguous as a result of callsto remap_pfn_range(). Instead, use the already existing host PTE lookup to retrieve a valid host-side mapping level after __kvm_faultin_pfn() has returned. Then find the largest size that will satisfy the guest's request while staying within a single host PTE. Signed-off-by: Paolo Bonzini --- arch/powerpc/kvm/e500_mmu_host.c | 180 ++++++++++++------------------- 1 file changed, 70 insertions(+), 110 deletions(-) diff --git a/arch/powerpc/kvm/e500_mmu_host.c b/arch/powerpc/kvm/e500_mmu_h= ost.c index 7752b7f24c51..0457bbc2526f 100644 --- a/arch/powerpc/kvm/e500_mmu_host.c +++ b/arch/powerpc/kvm/e500_mmu_host.c @@ -326,15 +326,14 @@ static inline int kvmppc_e500_shadow_map(struct kvmpp= c_vcpu_e500 *vcpu_e500, struct tlbe_ref *ref) { struct kvm_memory_slot *slot; - unsigned long pfn =3D 0; /* silence GCC warning */ + unsigned int psize; + unsigned long pfn; struct page *page =3D NULL; unsigned long hva; - int pfnmap =3D 0; int tsize =3D BOOK3E_PAGESZ_4K; int ret =3D 0; unsigned long mmu_seq; struct kvm *kvm =3D vcpu_e500->vcpu.kvm; - unsigned long tsize_pages =3D 0; pte_t *ptep; unsigned int wimg =3D 0; pgd_t *pgdir; @@ -361,111 +360,12 @@ static inline int kvmppc_e500_shadow_map(struct kvmp= pc_vcpu_e500 *vcpu_e500, =20 hva =3D gfn_to_hva_memslot(slot, gfn); =20 - if (tlbsel =3D=3D 1) { - struct vm_area_struct *vma; - mmap_read_lock(kvm->mm); - - vma =3D find_vma(kvm->mm, hva); - if (vma && hva >=3D vma->vm_start && - (vma->vm_flags & VM_PFNMAP)) { - /* - * This VMA is a physically contiguous region (e.g. - * /dev/mem) that bypasses normal Linux page - * management. Find the overlap between the - * vma and the memslot. - */ - - unsigned long start, end; - unsigned long slot_start, slot_end; - - pfnmap =3D 1; - writable =3D vma->vm_flags & VM_WRITE; - - start =3D vma->vm_pgoff; - end =3D start + - vma_pages(vma); - - pfn =3D start + ((hva - vma->vm_start) >> PAGE_SHIFT); - - slot_start =3D pfn - (gfn - slot->base_gfn); - slot_end =3D slot_start + slot->npages; - - if (start < slot_start) - start =3D slot_start; - if (end > slot_end) - end =3D slot_end; - - tsize =3D (gtlbe->mas1 & MAS1_TSIZE_MASK) >> - MAS1_TSIZE_SHIFT; - - /* - * e500 doesn't implement the lowest tsize bit, - * or 1K pages. - */ - tsize =3D max(BOOK3E_PAGESZ_4K, tsize & ~1); - - /* - * Now find the largest tsize (up to what the guest - * requested) that will cover gfn, stay within the - * range, and for which gfn and pfn are mutually - * aligned. - */ - - for (; tsize > BOOK3E_PAGESZ_4K; tsize -=3D 2) { - unsigned long gfn_start, gfn_end; - tsize_pages =3D 1UL << (tsize - 2); - - gfn_start =3D gfn & ~(tsize_pages - 1); - gfn_end =3D gfn_start + tsize_pages; - - if (gfn_start + pfn - gfn < start) - continue; - if (gfn_end + pfn - gfn > end) - continue; - if ((gfn & (tsize_pages - 1)) !=3D - (pfn & (tsize_pages - 1))) - continue; - - gvaddr &=3D ~((tsize_pages << PAGE_SHIFT) - 1); - pfn &=3D ~(tsize_pages - 1); - break; - } - } else if (vma && hva >=3D vma->vm_start && - is_vm_hugetlb_page(vma)) { - unsigned long psize =3D vma_kernel_pagesize(vma); - - tsize =3D (gtlbe->mas1 & MAS1_TSIZE_MASK) >> - MAS1_TSIZE_SHIFT; - - /* - * Take the largest page size that satisfies both host - * and guest mapping - */ - tsize =3D min(__ilog2(psize) - 10, tsize); - - /* - * e500 doesn't implement the lowest tsize bit, - * or 1K pages. - */ - tsize =3D max(BOOK3E_PAGESZ_4K, tsize & ~1); - } - - mmap_read_unlock(kvm->mm); - } - - if (likely(!pfnmap)) { - tsize_pages =3D 1UL << (tsize + 10 - PAGE_SHIFT); - pfn =3D __kvm_faultin_pfn(slot, gfn, FOLL_WRITE, &writable, &page); - if (is_error_noslot_pfn(pfn)) { - if (printk_ratelimit()) - pr_err("%s: real page not found for gfn %lx\n", - __func__, (long)gfn); - return -EINVAL; - } - - /* Align guest and physical address to page map boundaries */ - pfn &=3D ~(tsize_pages - 1); - gvaddr &=3D ~((tsize_pages << PAGE_SHIFT) - 1); + pfn =3D __kvm_faultin_pfn(slot, gfn, FOLL_WRITE, &writable, &page); + if (is_error_noslot_pfn(pfn)) { + if (printk_ratelimit()) + pr_err("%s: real page not found for gfn %lx\n", + __func__, (long)gfn); + return -EINVAL; } =20 spin_lock(&kvm->mmu_lock); @@ -483,7 +383,7 @@ static inline int kvmppc_e500_shadow_map(struct kvmppc_= vcpu_e500 *vcpu_e500, * can't run hence pfn won't change. */ local_irq_save(flags); - ptep =3D find_linux_pte(pgdir, hva, NULL, NULL); + ptep =3D find_linux_pte(pgdir, hva, NULL, &psize); if (ptep) { pte_t pte =3D READ_ONCE(*ptep); =20 @@ -500,6 +400,66 @@ static inline int kvmppc_e500_shadow_map(struct kvmppc= _vcpu_e500 *vcpu_e500, } } =20 + if (psize && tlbsel =3D=3D 1) { + unsigned long psize_pages, tsize_pages; + unsigned long start, end; + unsigned long slot_start, slot_end; + + psize_pages =3D 1UL << (psize - PAGE_SHIFT); + start =3D pfn & ~(psize_pages - 1); + end =3D start + psize_pages; + + slot_start =3D pfn - (gfn - slot->base_gfn); + slot_end =3D slot_start + slot->npages; + + if (start < slot_start) + start =3D slot_start; + if (end > slot_end) + end =3D slot_end; + + tsize =3D (gtlbe->mas1 & MAS1_TSIZE_MASK) >> + MAS1_TSIZE_SHIFT; + + /* + * Any page size that doesn't satisfy the host mapping + * will fail the start and end tests. + */ + tsize =3D min(psize - PAGE_SHIFT + BOOK3E_PAGESZ_4K, tsize); + + /* + * e500 doesn't implement the lowest tsize bit, + * or 1K pages. + */ + tsize =3D max(BOOK3E_PAGESZ_4K, tsize & ~1); + + /* + * Now find the largest tsize (up to what the guest + * requested) that will cover gfn, stay within the + * range, and for which gfn and pfn are mutually + * aligned. + */ + + for (; tsize > BOOK3E_PAGESZ_4K; tsize -=3D 2) { + unsigned long gfn_start, gfn_end; + tsize_pages =3D 1UL << (tsize - 2); + + gfn_start =3D gfn & ~(tsize_pages - 1); + gfn_end =3D gfn_start + tsize_pages; + + if (gfn_start + pfn - gfn < start) + continue; + if (gfn_end + pfn - gfn > end) + continue; + if ((gfn & (tsize_pages - 1)) !=3D + (pfn & (tsize_pages - 1))) + continue; + + gvaddr &=3D ~((tsize_pages << PAGE_SHIFT) - 1); + pfn &=3D ~(tsize_pages - 1); + break; + } + } + kvmppc_e500_ref_setup(ref, gtlbe, pfn, wimg, writable); kvmppc_e500_setup_stlbe(&vcpu_e500->vcpu, gtlbe, tsize, ref, gvaddr, stlbe); --=20 2.47.1