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Shutemov" X-Google-Original-From: "Kirill A. Shutemov" Received: by box.localdomain (Postfix, from userid 1000) id 03C94102F68; Tue, 20 Oct 2020 09:19:02 +0300 (+03) To: Dave Hansen , Andy Lutomirski , Peter Zijlstra , Paolo Bonzini , Sean Christopherson , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel Cc: David Rientjes , Andrea Arcangeli , Kees Cook , Will Drewry , "Edgecombe, Rick P" , "Kleen, Andi" , Liran Alon , Mike Rapoport , x86@kernel.org, kvm@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, "Kirill A. Shutemov" Subject: [RFCv2 09/16] KVM: mm: Introduce VM_KVM_PROTECTED Date: Tue, 20 Oct 2020 09:18:52 +0300 Message-Id: <20201020061859.18385-10-kirill.shutemov@linux.intel.com> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20201020061859.18385-1-kirill.shutemov@linux.intel.com> References: <20201020061859.18385-1-kirill.shutemov@linux.intel.com> MIME-Version: 1.0 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: The new VMA flag that indicate a VMA that is not accessible to userspace but usable by kernel with GUP if FOLL_KVM is specified. The FOLL_KVM is only used in the KVM code. The code has to know how to deal with such pages. Signed-off-by: Kirill A. Shutemov --- include/linux/mm.h | 8 ++++++++ mm/gup.c | 20 ++++++++++++++++---- mm/huge_memory.c | 20 ++++++++++++++++---- mm/memory.c | 3 +++ mm/mmap.c | 3 +++ virt/kvm/async_pf.c | 2 +- virt/kvm/kvm_main.c | 9 +++++---- 7 files changed, 52 insertions(+), 13 deletions(-) diff --git a/include/linux/mm.h b/include/linux/mm.h index 16b799a0522c..c8d8cdcbc425 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -342,6 +342,8 @@ extern unsigned int kobjsize(const void *objp); # define VM_MAPPED_COPY VM_ARCH_1 /* T if mapped copy of data (nommu mmap) */ #endif +#define VM_KVM_PROTECTED 0 + #ifndef VM_GROWSUP # define VM_GROWSUP VM_NONE #endif @@ -658,6 +660,11 @@ static inline bool vma_is_accessible(struct vm_area_struct *vma) return vma->vm_flags & VM_ACCESS_FLAGS; } +static inline bool vma_is_kvm_protected(struct vm_area_struct *vma) +{ + return vma->vm_flags & VM_KVM_PROTECTED; +} + #ifdef CONFIG_SHMEM /* * The vma_is_shmem is not inline because it is used only by slow @@ -2766,6 +2773,7 @@ struct page *follow_page(struct vm_area_struct *vma, unsigned long address, #define FOLL_SPLIT_PMD 0x20000 /* split huge pmd before returning */ #define FOLL_PIN 0x40000 /* pages must be released via unpin_user_page */ #define FOLL_FAST_ONLY 0x80000 /* gup_fast: prevent fall-back to slow gup */ +#define FOLL_KVM 0x100000 /* access to VM_KVM_PROTECTED VMAs */ /* * FOLL_PIN and FOLL_LONGTERM may be used in various combinations with each diff --git a/mm/gup.c b/mm/gup.c index e869c634cc9a..accf6db0c06f 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -384,10 +384,19 @@ static int follow_pfn_pte(struct vm_area_struct *vma, unsigned long address, * FOLL_FORCE can write to even unwritable pte's, but only * after we've gone through a COW cycle and they are dirty. */ -static inline bool can_follow_write_pte(pte_t pte, unsigned int flags) +static inline bool can_follow_write_pte(struct vm_area_struct *vma, + pte_t pte, unsigned int flags) { - return pte_write(pte) || - ((flags & FOLL_FORCE) && (flags & FOLL_COW) && pte_dirty(pte)); + if (pte_write(pte)) + return true; + + if ((flags & FOLL_FORCE) && (flags & FOLL_COW) && pte_dirty(pte)) + return true; + + if (!vma_is_kvm_protected(vma) || !(vma->vm_flags & VM_WRITE)) + return false; + + return (vma->vm_flags & VM_SHARED) || page_mapcount(pte_page(pte)) == 1; } static struct page *follow_page_pte(struct vm_area_struct *vma, @@ -430,7 +439,7 @@ static struct page *follow_page_pte(struct vm_area_struct *vma, } if ((flags & FOLL_NUMA) && pte_protnone(pte)) goto no_page; - if ((flags & FOLL_WRITE) && !can_follow_write_pte(pte, flags)) { + if ((flags & FOLL_WRITE) && !can_follow_write_pte(vma, pte, flags)) { pte_unmap_unlock(ptep, ptl); return NULL; } @@ -750,6 +759,9 @@ static struct page *follow_page_mask(struct vm_area_struct *vma, ctx->page_mask = 0; + if (vma_is_kvm_protected(vma) && (flags & FOLL_KVM)) + flags &= ~FOLL_NUMA; + /* make this handle hugepd */ page = follow_huge_addr(mm, address, flags & FOLL_WRITE); if (!IS_ERR(page)) { diff --git a/mm/huge_memory.c b/mm/huge_memory.c index da397779a6d4..ec8cf9a40cfd 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -1322,10 +1322,19 @@ vm_fault_t do_huge_pmd_wp_page(struct vm_fault *vmf, pmd_t orig_pmd) * FOLL_FORCE can write to even unwritable pmd's, but only * after we've gone through a COW cycle and they are dirty. */ -static inline bool can_follow_write_pmd(pmd_t pmd, unsigned int flags) +static inline bool can_follow_write_pmd(struct vm_area_struct *vma, + pmd_t pmd, unsigned int flags) { - return pmd_write(pmd) || - ((flags & FOLL_FORCE) && (flags & FOLL_COW) && pmd_dirty(pmd)); + if (pmd_write(pmd)) + return true; + + if ((flags & FOLL_FORCE) && (flags & FOLL_COW) && pmd_dirty(pmd)) + return true; + + if (!vma_is_kvm_protected(vma) || !(vma->vm_flags & VM_WRITE)) + return false; + + return (vma->vm_flags & VM_SHARED) || page_mapcount(pmd_page(pmd)) == 1; } struct page *follow_trans_huge_pmd(struct vm_area_struct *vma, @@ -1338,7 +1347,7 @@ struct page *follow_trans_huge_pmd(struct vm_area_struct *vma, assert_spin_locked(pmd_lockptr(mm, pmd)); - if (flags & FOLL_WRITE && !can_follow_write_pmd(*pmd, flags)) + if (flags & FOLL_WRITE && !can_follow_write_pmd(vma, *pmd, flags)) goto out; /* Avoid dumping huge zero page */ @@ -1412,6 +1421,9 @@ vm_fault_t do_huge_pmd_numa_page(struct vm_fault *vmf, pmd_t pmd) bool was_writable; int flags = 0; + if (vma_is_kvm_protected(vma)) + return VM_FAULT_SIGBUS; + vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd); if (unlikely(!pmd_same(pmd, *vmf->pmd))) goto out_unlock; diff --git a/mm/memory.c b/mm/memory.c index eeae590e526a..2c9756b4e52f 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -4165,6 +4165,9 @@ static vm_fault_t do_numa_page(struct vm_fault *vmf) bool was_writable = pte_savedwrite(vmf->orig_pte); int flags = 0; + if (vma_is_kvm_protected(vma)) + return VM_FAULT_SIGBUS; + /* * The "pte" at this point cannot be used safely without * validation through pte_unmap_same(). It's of NUMA type but diff --git a/mm/mmap.c b/mm/mmap.c index bdd19f5b994e..be699f688b6c 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -112,6 +112,9 @@ pgprot_t vm_get_page_prot(unsigned long vm_flags) (VM_READ|VM_WRITE|VM_EXEC|VM_SHARED)]) | pgprot_val(arch_vm_get_page_prot(vm_flags))); + if (vm_flags & VM_KVM_PROTECTED) + ret = PAGE_NONE; + return arch_filter_pgprot(ret); } EXPORT_SYMBOL(vm_get_page_prot); diff --git a/virt/kvm/async_pf.c b/virt/kvm/async_pf.c index dd777688d14a..85a2f99f6e9b 100644 --- a/virt/kvm/async_pf.c +++ b/virt/kvm/async_pf.c @@ -61,7 +61,7 @@ static void async_pf_execute(struct work_struct *work) * access remotely. */ mmap_read_lock(mm); - get_user_pages_remote(mm, addr, 1, FOLL_WRITE, NULL, NULL, + get_user_pages_remote(mm, addr, 1, FOLL_WRITE | FOLL_KVM, NULL, NULL, &locked); if (locked) mmap_read_unlock(mm); diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index a9884cb8c867..125db5a73e10 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -1794,7 +1794,7 @@ unsigned long kvm_vcpu_gfn_to_hva_prot(struct kvm_vcpu *vcpu, gfn_t gfn, bool *w static inline int check_user_page_hwpoison(unsigned long addr) { - int rc, flags = FOLL_HWPOISON | FOLL_WRITE; + int rc, flags = FOLL_HWPOISON | FOLL_WRITE | FOLL_KVM; rc = get_user_pages(addr, 1, flags, NULL, NULL); return rc == -EHWPOISON; @@ -1836,7 +1836,7 @@ static bool hva_to_pfn_fast(unsigned long addr, bool write_fault, static int hva_to_pfn_slow(unsigned long addr, bool *async, bool write_fault, bool *writable, kvm_pfn_t *pfn) { - unsigned int flags = FOLL_HWPOISON; + unsigned int flags = FOLL_HWPOISON | FOLL_KVM; struct page *page; int npages = 0; @@ -2327,7 +2327,7 @@ int copy_from_guest(void *data, unsigned long hva, int len, bool protected) check_object_size(data, len, false); while ((seg = next_segment(len, offset)) != 0) { - npages = get_user_pages_unlocked(hva, 1, &page, 0); + npages = get_user_pages_unlocked(hva, 1, &page, FOLL_KVM); if (npages != 1) return -EFAULT; memcpy(data, page_address(page) + offset, seg); @@ -2354,7 +2354,8 @@ int copy_to_guest(unsigned long hva, const void *data, int len, bool protected) check_object_size(data, len, true); while ((seg = next_segment(len, offset)) != 0) { - npages = get_user_pages_unlocked(hva, 1, &page, FOLL_WRITE); + npages = get_user_pages_unlocked(hva, 1, &page, + FOLL_WRITE | FOLL_KVM); if (npages != 1) return -EFAULT; memcpy(page_address(page) + offset, data, seg);