KVM: PPC: Book3S HV: Rework secure mem slot dropping (81ab595d) · Commits · 戴 / test

When a secure memslot is dropped, all the pages backed in the secure device (aka really backed by secure memory by the Ultravisor) should be paged out to a normal page. Previously, this was achieved by triggering the page fault mechanism which is calling kvmppc_svm_page_out() on each pages. This can't work when hot unplugging a memory slot because the memory slot is flagged as invalid and gfn_to_pfn() is then not trying to access the page, so the page fault mechanism is not triggered. Since the final goal is to make a call to kvmppc_svm_page_out() it seems simpler to call directly instead of triggering such a mechanism. This way kvmppc_uvmem_drop_pages() can be called even when hot unplugging a memslot. Since kvmppc_uvmem_drop_pages() is already holding kvm->arch.uvmem_lock, the call to __kvmppc_svm_page_out() is made. As __kvmppc_svm_page_out needs the vma pointer to migrate the pages, the VMA is fetched in a lazy way, to not trigger find_vma() all the time. In addition, the mmap_sem is held in read mode during that time, not in write mode since the virual memory layout is not impacted, and kvm->arch.uvmem_lock prevents concurrent operation on the secure device. Reviewed-by:

Bharata B Rao <bharata@linux.ibm.com> Signed-off-by:

Laurent Dufour <ldufour@linux.ibm.com> [modified check on the VMA in kvmppc_uvmem_drop_pages] Signed-off-by:

Ram Pai <linuxram@us.ibm.com> [modified the changelog description] Signed-off-by:

Paul Mackerras <paulus@ozlabs.org>

arch/powerpc/kvm/book3s_hv_uvmem.c

+35 −17

Original line number	Diff line number	Diff line
		@@ -594,35 +594,53 @@ static inline int kvmppc_svm_page_out(struct vm_area_struct *vma,
		* fault on them, do fault time migration to replace the device PTEs in
		* QEMU page table with normal PTEs from newly allocated pages.
		*/
		void kvmppc_uvmem_drop_pages(const struct kvm_memory_slot *free,
		void kvmppc_uvmem_drop_pages(const struct kvm_memory_slot *slot,
		struct kvm *kvm, bool skip_page_out)
		{
		int i;
		struct kvmppc_uvmem_page_pvt *pvt;
		unsigned long pfn, uvmem_pfn;
		unsigned long gfn = free->base_gfn;

		for (i = free->npages; i; --i, ++gfn) {
		struct page *uvmem_page;
		struct vm_area_struct *vma = NULL;
		unsigned long uvmem_pfn, gfn;
		unsigned long addr;

		mutex_lock(&kvm->arch.uvmem_lock);
		if (!kvmppc_gfn_is_uvmem_pfn(gfn, kvm, &uvmem_pfn)) {
		kvmppc_gfn_remove(gfn, kvm);
		mutex_unlock(&kvm->arch.uvmem_lock);
		continue;
		mmap_read_lock(kvm->mm);

		addr = slot->userspace_addr;

		gfn = slot->base_gfn;
		for (i = slot->npages; i; --i, ++gfn, addr += PAGE_SIZE) {

		/* Fetch the VMA if addr is not in the latest fetched one */
		if (!vma \|\| addr >= vma->vm_end) {
		vma = find_vma_intersection(kvm->mm, addr, addr+1);
		if (!vma) {
		pr_err("Can't find VMA for gfn:0x%lx\n", gfn);
		break;
		}
		}

		mutex_lock(&kvm->arch.uvmem_lock);

		if (kvmppc_gfn_is_uvmem_pfn(gfn, kvm, &uvmem_pfn)) {
		uvmem_page = pfn_to_page(uvmem_pfn);
		pvt = uvmem_page->zone_device_data;
		pvt->skip_page_out = skip_page_out;
		pvt->remove_gfn = true;
		mutex_unlock(&kvm->arch.uvmem_lock);

		pfn = gfn_to_pfn(kvm, gfn);
		if (is_error_noslot_pfn(pfn))
		continue;
		kvm_release_pfn_clean(pfn);
		if (__kvmppc_svm_page_out(vma, addr, addr + PAGE_SIZE,
		PAGE_SHIFT, kvm, pvt->gpa))
		pr_err("Can't page out gpa:0x%lx addr:0x%lx\n",
		pvt->gpa, addr);
		} else {
		/* Remove the shared flag if any */
		kvmppc_gfn_remove(gfn, kvm);
		}

		mutex_unlock(&kvm->arch.uvmem_lock);
		}

		mmap_read_unlock(kvm->mm);
		}

		unsigned long kvmppc_h_svm_init_abort(struct kvm *kvm)

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