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Message-ID: <20201023123712.GC392079@kernel.org>
Date: Fri, 23 Oct 2020 15:37:12 +0300
From: Mike Rapoport <rppt@...nel.org>
To: "Kirill A. Shutemov" <kirill@...temov.name>
Cc: Dave Hansen <dave.hansen@...ux.intel.com>,
Andy Lutomirski <luto@...nel.org>,
Peter Zijlstra <peterz@...radead.org>,
Paolo Bonzini <pbonzini@...hat.com>,
Sean Christopherson <sean.j.christopherson@...el.com>,
Vitaly Kuznetsov <vkuznets@...hat.com>,
Wanpeng Li <wanpengli@...cent.com>,
Jim Mattson <jmattson@...gle.com>,
Joerg Roedel <joro@...tes.org>,
David Rientjes <rientjes@...gle.com>,
Andrea Arcangeli <aarcange@...hat.com>,
Kees Cook <keescook@...omium.org>,
Will Drewry <wad@...omium.org>,
"Edgecombe, Rick P" <rick.p.edgecombe@...el.com>,
"Kleen, Andi" <andi.kleen@...el.com>,
Liran Alon <liran.alon@...cle.com>, x86@...nel.org,
kvm@...r.kernel.org, linux-mm@...ck.org,
linux-kernel@...r.kernel.org,
"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Subject: Re: [RFCv2 15/16] KVM: Unmap protected pages from direct mapping
On Tue, Oct 20, 2020 at 09:18:58AM +0300, Kirill A. Shutemov wrote:
> If the protected memory feature enabled, unmap guest memory from
> kernel's direct mappings.
>
> Migration and KSM is disabled for protected memory as it would require a
> special treatment.
>
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
> ---
> include/linux/mm.h | 3 +++
> mm/huge_memory.c | 8 ++++++++
> mm/ksm.c | 2 ++
> mm/memory.c | 12 ++++++++++++
> mm/rmap.c | 4 ++++
> virt/lib/mem_protected.c | 21 +++++++++++++++++++++
> 6 files changed, 50 insertions(+)
>
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index ee274d27e764..74efc51e63f0 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -671,6 +671,9 @@ static inline bool vma_is_kvm_protected(struct vm_area_struct *vma)
> return vma->vm_flags & VM_KVM_PROTECTED;
> }
>
> +void kvm_map_page(struct page *page, int nr_pages);
> +void kvm_unmap_page(struct page *page, int nr_pages);
This still does not seem right ;-)
And I still think that map/unmap primitives shoud be a part of the
generic mm rather than exported by KVM.
> +
> #ifdef CONFIG_SHMEM
> /*
> * The vma_is_shmem is not inline because it is used only by slow
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index ec8cf9a40cfd..40974656cb43 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -627,6 +627,10 @@ static vm_fault_t __do_huge_pmd_anonymous_page(struct vm_fault *vmf,
> spin_unlock(vmf->ptl);
> count_vm_event(THP_FAULT_ALLOC);
> count_memcg_event_mm(vma->vm_mm, THP_FAULT_ALLOC);
> +
> + /* Unmap page from direct mapping */
> + if (vma_is_kvm_protected(vma))
> + kvm_unmap_page(page, HPAGE_PMD_NR);
> }
>
> return 0;
> @@ -1689,6 +1693,10 @@ int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
> page_remove_rmap(page, true);
> VM_BUG_ON_PAGE(page_mapcount(page) < 0, page);
> VM_BUG_ON_PAGE(!PageHead(page), page);
> +
> + /* Map the page back to the direct mapping */
> + if (vma_is_kvm_protected(vma))
> + kvm_map_page(page, HPAGE_PMD_NR);
> } else if (thp_migration_supported()) {
> swp_entry_t entry;
>
> diff --git a/mm/ksm.c b/mm/ksm.c
> index 9afccc36dbd2..c720e271448f 100644
> --- a/mm/ksm.c
> +++ b/mm/ksm.c
> @@ -528,6 +528,8 @@ static struct vm_area_struct *find_mergeable_vma(struct mm_struct *mm,
> return NULL;
> if (!(vma->vm_flags & VM_MERGEABLE) || !vma->anon_vma)
> return NULL;
> + if (vma_is_kvm_protected(vma))
> + return NULL;
> return vma;
> }
>
> diff --git a/mm/memory.c b/mm/memory.c
> index 2c9756b4e52f..e28bd5f902a7 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -1245,6 +1245,11 @@ static unsigned long zap_pte_range(struct mmu_gather *tlb,
> likely(!(vma->vm_flags & VM_SEQ_READ)))
> mark_page_accessed(page);
> }
> +
> + /* Map the page back to the direct mapping */
> + if (vma_is_anonymous(vma) && vma_is_kvm_protected(vma))
> + kvm_map_page(page, 1);
> +
> rss[mm_counter(page)]--;
> page_remove_rmap(page, false);
> if (unlikely(page_mapcount(page) < 0))
> @@ -3466,6 +3471,7 @@ static vm_fault_t do_anonymous_page(struct vm_fault *vmf)
> struct page *page;
> vm_fault_t ret = 0;
> pte_t entry;
> + bool set = false;
>
> /* File mapping without ->vm_ops ? */
> if (vma->vm_flags & VM_SHARED)
> @@ -3554,6 +3560,7 @@ static vm_fault_t do_anonymous_page(struct vm_fault *vmf)
> inc_mm_counter_fast(vma->vm_mm, MM_ANONPAGES);
> page_add_new_anon_rmap(page, vma, vmf->address, false);
> lru_cache_add_inactive_or_unevictable(page, vma);
> + set = true;
> setpte:
> set_pte_at(vma->vm_mm, vmf->address, vmf->pte, entry);
>
> @@ -3561,6 +3568,11 @@ static vm_fault_t do_anonymous_page(struct vm_fault *vmf)
> update_mmu_cache(vma, vmf->address, vmf->pte);
> unlock:
> pte_unmap_unlock(vmf->pte, vmf->ptl);
> +
> + /* Unmap page from direct mapping */
> + if (vma_is_kvm_protected(vma) && set)
> + kvm_unmap_page(page, 1);
> +
> return ret;
> release:
> put_page(page);
> diff --git a/mm/rmap.c b/mm/rmap.c
> index 9425260774a1..247548d6d24b 100644
> --- a/mm/rmap.c
> +++ b/mm/rmap.c
> @@ -1725,6 +1725,10 @@ static bool try_to_unmap_one(struct page *page, struct vm_area_struct *vma,
>
> static bool invalid_migration_vma(struct vm_area_struct *vma, void *arg)
> {
> + /* TODO */
> + if (vma_is_kvm_protected(vma))
> + return true;
> +
> return vma_is_temporary_stack(vma);
> }
>
> diff --git a/virt/lib/mem_protected.c b/virt/lib/mem_protected.c
> index 1dfe82534242..9d2ef99285e5 100644
> --- a/virt/lib/mem_protected.c
> +++ b/virt/lib/mem_protected.c
> @@ -30,6 +30,27 @@ void kvm_unmap_page_atomic(void *vaddr)
> }
> EXPORT_SYMBOL_GPL(kvm_unmap_page_atomic);
>
> +void kvm_map_page(struct page *page, int nr_pages)
> +{
> + int i;
> +
> + /* Clear page before returning it to the direct mapping */
> + for (i = 0; i < nr_pages; i++) {
> + void *p = kvm_map_page_atomic(page + i);
> + memset(p, 0, PAGE_SIZE);
> + kvm_unmap_page_atomic(p);
> + }
> +
> + kernel_map_pages(page, nr_pages, 1);
> +}
> +EXPORT_SYMBOL_GPL(kvm_map_page);
> +
> +void kvm_unmap_page(struct page *page, int nr_pages)
> +{
> + kernel_map_pages(page, nr_pages, 0);
> +}
> +EXPORT_SYMBOL_GPL(kvm_unmap_page);
> +
> int kvm_init_protected_memory(void)
> {
> guest_map_ptes = kmalloc_array(num_possible_cpus(),
> --
> 2.26.2
>
>
--
Sincerely yours,
Mike.
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