5.15-stable review patch. If anyone has any objections, please let me know.
------------------
From: Juergen Gross jgross@suse.com
[ 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@suse.com Tested-by: Alan Robinson Alan.Robinson@fujitsu.com Reviewed-by: Jan Beulich jbeulich@suse.com Signed-off-by: Juergen Gross jgross@suse.com Signed-off-by: Sasha Levin sashal@kernel.org --- 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 03c9ec0212c9e..f88071566cac5 100644 --- a/arch/x86/xen/mmu_pv.c +++ b/arch/x86/xen/mmu_pv.c @@ -95,6 +95,51 @@ 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: * @@ -791,6 +836,9 @@ static void __init xen_after_bootmem(void) static_branch_enable(&xen_struct_pages_ready); SetPagePinned(virt_to_page(level3_user_vsyscall)); 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, @@ -2151,10 +2199,6 @@ 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, @@ -2271,18 +2315,25 @@ 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);
@@ -2306,12 +2357,12 @@ 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); @@ -2319,6 +2370,8 @@ 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(vstart);