From 2cd1c8d4dc7ecca9e9431e2dabe41ae9c7d89e51 Mon Sep 17 00:00:00 2001 From: Konrad Rzeszutek Wilk Date: Tue, 15 Nov 2011 14:49:09 -0800 Subject: x86/paravirt: PTE updates in k(un)map_atomic need to be synchronous, regardless of lazy_mmu mode Fix an outstanding issue that has been reported since 2.6.37. Under a heavy loaded machine processing "fork()" calls could crash with: BUG: unable to handle kernel paging request at f573fc8c IP: [] swap_count_continued+0x104/0x180 *pdpt = 000000002a3b9027 *pde = 0000000001bed067 *pte = 0000000000000000 Oops: 0000 [#1] SMP Modules linked in: Pid: 1638, comm: apache2 Not tainted 3.0.4-linode37 #1 EIP: 0061:[] EFLAGS: 00210246 CPU: 3 EIP is at swap_count_continued+0x104/0x180 .. snip.. Call Trace: [] ? __swap_duplicate+0xc2/0x160 [] ? pte_mfn_to_pfn+0x87/0xe0 [] ? swap_duplicate+0x14/0x40 [] ? copy_pte_range+0x45b/0x500 [] ? copy_page_range+0x195/0x200 [] ? dup_mmap+0x1c6/0x2c0 [] ? dup_mm+0xa8/0x130 [] ? copy_process+0x98a/0xb30 [] ? do_fork+0x4f/0x280 [] ? getnstimeofday+0x43/0x100 [] ? sys_clone+0x30/0x40 [] ? ptregs_clone+0x15/0x48 [] ? syscall_call+0x7/0xb The problem is that in copy_page_range() we turn lazy mode on, and then in swap_entry_free() we call swap_count_continued() which ends up in: map = kmap_atomic(page, KM_USER0) + offset; and then later we touch *map. Since we are running in batched mode (lazy) we don't actually set up the PTE mappings and the kmap_atomic is not done synchronously and ends up trying to dereference a page that has not been set. Looking at kmap_atomic_prot_pfn(), it uses 'arch_flush_lazy_mmu_mode' and doing the same in kmap_atomic_prot() and __kunmap_atomic() makes the problem go away. Interestingly, commit b8bcfe997e4615 ("x86/paravirt: remove lazy mode in interrupts") removed part of this to fix an interrupt issue - but it went to far and did not consider this scenario. Signed-off-by: Konrad Rzeszutek Wilk Cc: Peter Zijlstra Cc: Jeremy Fitzhardinge Cc: Signed-off-by: Andrew Morton Signed-off-by: Ingo Molnar --- arch/x86/mm/highmem_32.c | 2 ++ 1 file changed, 2 insertions(+) (limited to 'arch/x86/mm') diff --git a/arch/x86/mm/highmem_32.c b/arch/x86/mm/highmem_32.c index b49962662101..f4f29b19fac5 100644 --- a/arch/x86/mm/highmem_32.c +++ b/arch/x86/mm/highmem_32.c @@ -45,6 +45,7 @@ void *kmap_atomic_prot(struct page *page, pgprot_t prot) vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx); BUG_ON(!pte_none(*(kmap_pte-idx))); set_pte(kmap_pte-idx, mk_pte(page, prot)); + arch_flush_lazy_mmu_mode(); return (void *)vaddr; } @@ -88,6 +89,7 @@ void __kunmap_atomic(void *kvaddr) */ kpte_clear_flush(kmap_pte-idx, vaddr); kmap_atomic_idx_pop(); + arch_flush_lazy_mmu_mode(); } #ifdef CONFIG_DEBUG_HIGHMEM else { -- cgit v1.2.3 From b6999b19120931ede364fa3b685e698a61fed31d Mon Sep 17 00:00:00 2001 From: Youquan Song Date: Thu, 8 Dec 2011 14:34:16 -0800 Subject: thp: add compound tail page _mapcount when mapped With the 3.2-rc kernel, IOMMU 2M pages in KVM works. But when I tried to use IOMMU 1GB pages in KVM, I encountered an oops and the 1GB page failed to be used. The root cause is that 1GB page allocation calls gup_huge_pud() while 2M page calls gup_huge_pmd. If compound pages are used and the page is a tail page, gup_huge_pmd() increases _mapcount to record tail page are mapped while gup_huge_pud does not do that. So when the mapped page is relesed, it will result in kernel oops because the page is not marked mapped. This patch add tail process for compound page in 1GB huge page which keeps the same process as 2M page. Reproduce like: 1. Add grub boot option: hugepagesz=1G hugepages=8 2. mount -t hugetlbfs -o pagesize=1G hugetlbfs /dev/hugepages 3. qemu-kvm -m 2048 -hda os-kvm.img -cpu kvm64 -smp 4 -mem-path /dev/hugepages -net none -device pci-assign,host=07:00.1 kernel BUG at mm/swap.c:114! invalid opcode: 0000 [#1] SMP Call Trace: put_page+0x15/0x37 kvm_release_pfn_clean+0x31/0x36 kvm_iommu_put_pages+0x94/0xb1 kvm_iommu_unmap_memslots+0x80/0xb6 kvm_assign_device+0xba/0x117 kvm_vm_ioctl_assigned_device+0x301/0xa47 kvm_vm_ioctl+0x36c/0x3a2 do_vfs_ioctl+0x49e/0x4e4 sys_ioctl+0x5a/0x7c system_call_fastpath+0x16/0x1b RIP put_compound_page+0xd4/0x168 Signed-off-by: Youquan Song Reviewed-by: Andrea Arcangeli Cc: Andi Kleen Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- arch/x86/mm/gup.c | 2 ++ 1 file changed, 2 insertions(+) (limited to 'arch/x86/mm') diff --git a/arch/x86/mm/gup.c b/arch/x86/mm/gup.c index ea305856151c..dd74e46828c0 100644 --- a/arch/x86/mm/gup.c +++ b/arch/x86/mm/gup.c @@ -201,6 +201,8 @@ static noinline int gup_huge_pud(pud_t pud, unsigned long addr, do { VM_BUG_ON(compound_head(page) != head); pages[*nr] = page; + if (PageTail(page)) + get_huge_page_tail(page); (*nr)++; page++; refs++; -- cgit v1.2.3