Commit aa3ade42 authored by Balbir Singh's avatar Balbir Singh Committed by Andrew Morton
Browse files

lib/test_hmm: add large page allocation failure testing 

Add HMM_DMIRROR_FLAG_FAIL_ALLOC flag to simulate large page allocation
failures, enabling testing of split migration code paths.

This test flag allows validation of the fallback behavior when destination
device cannot allocate compound pages.  This is useful for testing the
split migration functionality.

Link: https://lkml.kernel.org/r/20251001065707.920170-13-balbirs@nvidia.com


Signed-off-by: default avatarBalbir Singh <balbirs@nvidia.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Zi Yan <ziy@nvidia.com>
Cc: Joshua Hahn <joshua.hahnjy@gmail.com>
Cc: Rakie Kim <rakie.kim@sk.com>
Cc: Byungchul Park <byungchul@sk.com>
Cc: Gregory Price <gourry@gourry.net>
Cc: Ying Huang <ying.huang@linux.alibaba.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: "Liam R. Howlett" <Liam.Howlett@oracle.com>
Cc: Nico Pache <npache@redhat.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Dev Jain <dev.jain@arm.com>
Cc: Barry Song <baohua@kernel.org>
Cc: Lyude Paul <lyude@redhat.com>
Cc: Danilo Krummrich <dakr@kernel.org>
Cc: David Airlie <airlied@gmail.com>
Cc: Simona Vetter <simona@ffwll.ch>
Cc: Ralph Campbell <rcampbell@nvidia.com>
Cc: Mika Penttilä <mpenttil@redhat.com>
Cc: Matthew Brost <matthew.brost@intel.com>
Cc: Francois Dugast <francois.dugast@intel.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 4265d67e

lib/test_hmm.c

+41 −20
Original line number Diff line number Diff line
@@ -92,6 +92,7 @@ struct dmirror { 
	struct xarray			pt;

	struct mmu_interval_notifier	notifier;

	struct mutex			mutex;

	__u64			flags;

};



/*
@@ -699,7 +700,12 @@ static void dmirror_migrate_alloc_and_copy(struct migrate_vma *args, 
		     page_to_pfn(spage)))

			goto next;



		if (dmirror->flags & HMM_DMIRROR_FLAG_FAIL_ALLOC) {

			dmirror->flags &= ~HMM_DMIRROR_FLAG_FAIL_ALLOC;

			dpage = NULL;

		} else

			dpage = dmirror_devmem_alloc_page(dmirror, is_large);



		if (!dpage) {

			struct folio *folio;

			unsigned long i;
@@ -959,44 +965,55 @@ static vm_fault_t dmirror_devmem_fault_alloc_and_copy(struct migrate_vma *args, 


		spage = BACKING_PAGE(spage);

		order = folio_order(page_folio(spage));



		if (order)

			*dst = MIGRATE_PFN_COMPOUND;

		if (*src & MIGRATE_PFN_WRITE)

			*dst |= MIGRATE_PFN_WRITE;



		if (dmirror->flags & HMM_DMIRROR_FLAG_FAIL_ALLOC) {

			dmirror->flags &= ~HMM_DMIRROR_FLAG_FAIL_ALLOC;

			*dst &= ~MIGRATE_PFN_COMPOUND;

			dpage = NULL;

		} else if (order) {

			dpage = folio_page(vma_alloc_folio(GFP_HIGHUSER_MOVABLE,

						order, args->vma, addr), 0);

		else

		} else {

			dpage = alloc_page_vma(GFP_HIGHUSER_MOVABLE, args->vma, addr);

		}



		/* Try with smaller pages if large allocation fails */

		if (!dpage && order) {

			dpage = alloc_page_vma(GFP_HIGHUSER_MOVABLE, args->vma, addr);

			if (!dpage)

		if (!dpage && !order)

			return VM_FAULT_OOM;

			order = 0;

		}



		pr_debug("migrating from sys to dev pfn src: 0x%lx pfn dst: 0x%lx\n",

				page_to_pfn(spage), page_to_pfn(dpage));



		if (dpage) {

			lock_page(dpage);

		xa_erase(&dmirror->pt, addr >> PAGE_SHIFT);

		copy_highpage(dpage, spage);

		*dst = migrate_pfn(page_to_pfn(dpage));

		if (*src & MIGRATE_PFN_WRITE)

			*dst |= MIGRATE_PFN_WRITE;

		if (order)

			*dst |= MIGRATE_PFN_COMPOUND;

			*dst |= migrate_pfn(page_to_pfn(dpage));

		}



		for (i = 0; i < (1 << order); i++) {

			struct page *src_page;

			struct page *dst_page;



			src_page = pfn_to_page(page_to_pfn(spage) + i);

			/* Try with smaller pages if large allocation fails */

			if (!dpage && order) {

				dpage = alloc_page_vma(GFP_HIGHUSER_MOVABLE, args->vma, addr);

				lock_page(dpage);

				dst[i] = migrate_pfn(page_to_pfn(dpage));

				dst_page = pfn_to_page(page_to_pfn(dpage));

				dpage = NULL; /* For the next iteration */

			} else {

				dst_page = pfn_to_page(page_to_pfn(dpage) + i);

			}



			src_page = pfn_to_page(page_to_pfn(spage) + i);



			xa_erase(&dmirror->pt, addr >> PAGE_SHIFT);

			addr += PAGE_SIZE;

			copy_highpage(dst_page, src_page);

		}

next:

		addr += PAGE_SIZE << order;

		src += 1 << order;

		dst += 1 << order;

	}
@@ -1514,6 +1531,10 @@ static long dmirror_fops_unlocked_ioctl(struct file *filp, 
		dmirror_device_remove_chunks(dmirror->mdevice);

		ret = 0;

		break;

	case HMM_DMIRROR_FLAGS:

		dmirror->flags = cmd.npages;

		ret = 0;

		break;



	default:

		return -EINVAL;

lib/test_hmm_uapi.h

+3 −0
Original line number Diff line number Diff line
@@ -37,6 +37,9 @@ struct hmm_dmirror_cmd { 
#define HMM_DMIRROR_EXCLUSIVE		_IOWR('H', 0x05, struct hmm_dmirror_cmd)

#define HMM_DMIRROR_CHECK_EXCLUSIVE	_IOWR('H', 0x06, struct hmm_dmirror_cmd)

#define HMM_DMIRROR_RELEASE		_IOWR('H', 0x07, struct hmm_dmirror_cmd)

#define HMM_DMIRROR_FLAGS		_IOWR('H', 0x08, struct hmm_dmirror_cmd)



#define HMM_DMIRROR_FLAG_FAIL_ALLOC	(1ULL << 0)



/*

 * Values returned in hmm_dmirror_cmd.ptr for HMM_DMIRROR_SNAPSHOT.