Commit e93ec872 authored by Juergen Gross's avatar Juergen Gross
Browse files

x86/xen: allow larger contiguous memory regions in PV guests 



Today a PV guest (including dom0) can create 2MB contiguous memory
regions for DMA buffers at max. This has led to problems at least
with the megaraid_sas driver, which wants to allocate a 2.3MB DMA
buffer.

The limiting factor is the frame array used to do the hypercall for
making the memory contiguous, which has 512 entries and is just a
static array in mmu_pv.c.

In order to not waste memory for non-PV guests, put the initial
frame array into .init.data section and dynamically allocate an array
from the .init_after_bootmem hook of PV guests.

In case a contiguous memory area larger than the initially supported
2MB is requested, allocate a larger buffer for the frame list. Note
that such an allocation is tried only after memory management has been
initialized properly, which is tested via a flag being set in the
.init_after_bootmem hook.

Fixes: 9f40ec84 ("xen/swiotlb: add alignment check for dma buffers")
Signed-off-by: default avatarJuergen Gross <jgross@suse.com>
Tested-by: default avatarAlan Robinson <Alan.Robinson@fujitsu.com>
Reviewed-by: default avatarJan Beulich <jbeulich@suse.com>
Signed-off-by: default avatarJuergen Gross <jgross@suse.com>
parent 85fcb57c

arch/x86/xen/mmu_pv.c

+62 −9
Original line number Diff line number Diff line
@@ -111,6 +111,51 @@ static pud_t level3_user_vsyscall[PTRS_PER_PUD] __page_aligned_bss; 
 */

static DEFINE_SPINLOCK(xen_reservation_lock);



/* Protected by xen_reservation_lock. */

#define MIN_CONTIG_ORDER 9 /* 2MB */

static unsigned int discontig_frames_order = MIN_CONTIG_ORDER;

static unsigned long discontig_frames_early[1UL << MIN_CONTIG_ORDER] __initdata;

static unsigned long *discontig_frames __refdata = discontig_frames_early;

static bool discontig_frames_dyn;



static int alloc_discontig_frames(unsigned int order)

{

	unsigned long *new_array, *old_array;

	unsigned int old_order;

	unsigned long flags;



	BUG_ON(order < MIN_CONTIG_ORDER);

	BUILD_BUG_ON(sizeof(discontig_frames_early) != PAGE_SIZE);



	new_array = (unsigned long *)__get_free_pages(GFP_KERNEL,

						      order - MIN_CONTIG_ORDER);

	if (!new_array)

		return -ENOMEM;



	spin_lock_irqsave(&xen_reservation_lock, flags);



	old_order = discontig_frames_order;



	if (order > discontig_frames_order || !discontig_frames_dyn) {

		if (!discontig_frames_dyn)

			old_array = NULL;

		else

			old_array = discontig_frames;



		discontig_frames = new_array;

		discontig_frames_order = order;

		discontig_frames_dyn = true;

	} else {

		old_array = new_array;

	}



	spin_unlock_irqrestore(&xen_reservation_lock, flags);



	free_pages((unsigned long)old_array, old_order - MIN_CONTIG_ORDER);



	return 0;

}



/*

 * Note about cr3 (pagetable base) values:

 *
@@ -814,6 +859,9 @@ static void __init xen_after_bootmem(void) 
	SetPagePinned(virt_to_page(level3_user_vsyscall));

#endif

	xen_pgd_walk(&init_mm, xen_mark_pinned, FIXADDR_TOP);



	if (alloc_discontig_frames(MIN_CONTIG_ORDER))

		BUG();

}



static void xen_unpin_page(struct mm_struct *mm, struct page *page,
@@ -2203,10 +2251,6 @@ void __init xen_init_mmu_ops(void) 
	memset(dummy_mapping, 0xff, PAGE_SIZE);

}



/* Protected by xen_reservation_lock. */

#define MAX_CONTIG_ORDER 9 /* 2MB */

static unsigned long discontig_frames[1<<MAX_CONTIG_ORDER];



#define VOID_PTE (mfn_pte(0, __pgprot(0)))

static void xen_zap_pfn_range(unsigned long vaddr, unsigned int order,

				unsigned long *in_frames,
@@ -2323,18 +2367,25 @@ int xen_create_contiguous_region(phys_addr_t pstart, unsigned int order, 
				 unsigned int address_bits,

				 dma_addr_t *dma_handle)

{

	unsigned long *in_frames = discontig_frames, out_frame;

	unsigned long *in_frames, out_frame;

	unsigned long  flags;

	int            success;

	unsigned long vstart = (unsigned long)phys_to_virt(pstart);



	if (unlikely(order > MAX_CONTIG_ORDER))

	if (unlikely(order > discontig_frames_order)) {

		if (!discontig_frames_dyn)

			return -ENOMEM;



		if (alloc_discontig_frames(order))

			return -ENOMEM;

	}



	memset((void *) vstart, 0, PAGE_SIZE << order);



	spin_lock_irqsave(&xen_reservation_lock, flags);



	in_frames = discontig_frames;



	/* 1. Zap current PTEs, remembering MFNs. */

	xen_zap_pfn_range(vstart, order, in_frames, NULL);
@@ -2358,12 +2409,12 @@ int xen_create_contiguous_region(phys_addr_t pstart, unsigned int order, 


void xen_destroy_contiguous_region(phys_addr_t pstart, unsigned int order)

{

	unsigned long *out_frames = discontig_frames, in_frame;

	unsigned long *out_frames, in_frame;

	unsigned long  flags;

	int success;

	unsigned long vstart;



	if (unlikely(order > MAX_CONTIG_ORDER))

	if (unlikely(order > discontig_frames_order))

		return;



	vstart = (unsigned long)phys_to_virt(pstart);
@@ -2371,6 +2422,8 @@ void xen_destroy_contiguous_region(phys_addr_t pstart, unsigned int order) 


	spin_lock_irqsave(&xen_reservation_lock, flags);



	out_frames = discontig_frames;



	/* 1. Find start MFN of contiguous extent. */

	in_frame = virt_to_mfn((void *)vstart);