6.6-stable review patch. If anyone has any objections, please let me know.
------------------
From: Juergen Gross <jgross@xxxxxxxx>
[ Upstream commit e93ec87286bd1fd30b7389e7a387cfb259f297e3 ]
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: 9f40ec84a797 ("xen/swiotlb: add alignment check for dma buffers")
Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
Tested-by: Alan Robinson <Alan.Robinson@xxxxxxxxxxx>
Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
arch/x86/xen/mmu_pv.c | 71 +++++++++++++++++++++++++++++++++++++------
1 file changed, 62 insertions(+), 9 deletions(-)
diff --git a/arch/x86/xen/mmu_pv.c b/arch/x86/xen/mmu_pv.c
index 6b201e64d8abc..2db46626acea2 100644
--- a/arch/x86/xen/mmu_pv.c
+++ b/arch/x86/xen/mmu_pv.c
@@ -113,6 +113,51 @@ 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:
*
@@ -813,6 +858,9 @@ 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,
@@ -2199,10 +2247,6 @@ 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,
@@ -2319,18 +2363,25 @@ 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))
- return -ENOMEM;
+ 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);
@@ -2354,12 +2405,12 @@ 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);
@@ -2367,6 +2418,8 @@ 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);
--
2.39.5
