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SubjectRe: [PATCH v6 03/11] mm, x86: Add support for eXclusive Page Frame Ownership (XPFO)
Hi all,

On Thu, Sep 07, 2017 at 11:36:01AM -0600, Tycho Andersen wrote:
>
> +inline void xpfo_flush_kernel_tlb(struct page *page, int order)
> +{
> + int level;
> + unsigned long size, kaddr;
> +
> + kaddr = (unsigned long)page_address(page);
> +
> + if (unlikely(!lookup_address(kaddr, &level))) {
> + WARN(1, "xpfo: invalid address to flush %lx %d\n", kaddr, level);
> + return;
> + }
> +
> + switch (level) {
> + case PG_LEVEL_4K:
> + size = PAGE_SIZE;
> + break;
> + case PG_LEVEL_2M:
> + size = PMD_SIZE;
> + break;
> + case PG_LEVEL_1G:
> + size = PUD_SIZE;
> + break;
> + default:
> + WARN(1, "xpfo: unsupported page level %x\n", level);
> + return;
> + }
> +
> + flush_tlb_kernel_range(kaddr, kaddr + (1 << order) * size);

Marco was testing and got the stack trace below. The issue is that on x86,
flush_tlb_kernel_range uses on_each_cpu, which causes the WARN() below. Since
this is called from xpfo_kmap/unmap in this interrupt handler, the WARN()
triggers.

I'm not sure what to do about this -- based on the discussion in v6 we need to
flush the TLBs for all CPUs -- but we can't do that with interrupts disabled,
which basically means with this we wouldn't be able to map/unmap pages in
interrupts.

Any thoughts?

Tycho

[ 2.712912] ------------[ cut here ]------------
[ 2.712922] WARNING: CPU: 0 PID: 0 at kernel/smp.c:414
smp_call_function_many+0x9a/0x270
[ 2.712923] Modules linked in: sd_mod ata_generic pata_acpi qxl
drm_kms_helper syscopyarea sysfillrect virtio_console sysimgblt
virtio_blk fb_sys_fops ttm drm 8139too ata_piix libata 8139cp
virtio_pci virtio_ring virtio mii crc32c_intel i2c_core serio_raw
floppy dm_mirror dm_region_hash dm_log dm_mod
[ 2.712939] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.13.0+ #8
[ 2.712940] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996),
BIOS 1.9.3-1.fc25 04/01/2014
[ 2.712941] task: ffffffff81c10480 task.stack: ffffffff81c00000
[ 2.712943] RIP: 0010:smp_call_function_many+0x9a/0x270
[ 2.712944] RSP: 0018:ffff88023fc03b38 EFLAGS: 00010046
[ 2.712945] RAX: 0000000000000000 RBX: ffffffff81072a50 RCX: 0000000000000001
[ 2.712946] RDX: ffff88023fc03ba8 RSI: ffffffff81072a50 RDI: ffffffff81e22320
[ 2.712947] RBP: ffff88023fc03b70 R08: 0000000000000970 R09: 0000000000000063
[ 2.712948] R10: ffff880000000970 R11: 0000000000000000 R12: ffff88023fc03ba8
[ 2.712949] R13: 0000000000000000 R14: ffff8802332b8e18 R15: ffffffff81e22320
[ 2.712950] FS: 0000000000000000(0000) GS:ffff88023fc00000(0000)
knlGS:0000000000000000
[ 2.712951] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 2.712951] CR2: 00007fde22f6b000 CR3: 000000022727b000 CR4: 00000000003406f0
[ 2.712954] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[ 2.712955] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[ 2.712955] Call Trace:
[ 2.712959] <IRQ>
[ 2.712964] ? x86_configure_nx+0x50/0x50
[ 2.712966] on_each_cpu+0x2d/0x60
[ 2.712967] flush_tlb_kernel_range+0x79/0x80
[ 2.712969] xpfo_flush_kernel_tlb+0xaa/0xe0
[ 2.712975] xpfo_kunmap+0xa8/0xc0
[ 2.712981] swiotlb_bounce+0xd1/0x1c0
[ 2.712982] swiotlb_tbl_unmap_single+0x10f/0x120
[ 2.712984] unmap_single+0x20/0x30
[ 2.712985] swiotlb_unmap_sg_attrs+0x46/0x70
[ 2.712991] __ata_qc_complete+0xfa/0x150 [libata]
[ 2.712994] ata_qc_complete+0xd2/0x2e0 [libata]
[ 2.712998] ata_hsm_qc_complete+0x6f/0x90 [libata]
[ 2.713004] ata_sff_hsm_move+0xae/0x6b0 [libata]
[ 2.713009] __ata_sff_port_intr+0x8e/0x100 [libata]
[ 2.713013] ata_bmdma_port_intr+0x2f/0xd0 [libata]
[ 2.713019] ata_bmdma_interrupt+0x161/0x1b0 [libata]
[ 2.713022] __handle_irq_event_percpu+0x3c/0x190
[ 2.713024] handle_irq_event_percpu+0x32/0x80
[ 2.713026] handle_irq_event+0x3b/0x60
[ 2.713027] handle_edge_irq+0x8f/0x190
[ 2.713029] handle_irq+0xab/0x120
[ 2.713032] ? _local_bh_enable+0x21/0x30
[ 2.713039] do_IRQ+0x48/0xd0
[ 2.713040] common_interrupt+0x93/0x93
[ 2.713042] RIP: 0010:native_safe_halt+0x6/0x10
[ 2.713043] RSP: 0018:ffffffff81c03de0 EFLAGS: 00000246 ORIG_RAX:
ffffffffffffffc1
[ 2.713044] RAX: 0000000000000000 RBX: ffffffff81c10480 RCX: 0000000000000000
[ 2.713045] RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
[ 2.713046] RBP: ffffffff81c03de0 R08: 00000000b656100b R09: 0000000000000000
[ 2.713047] R10: 0000000000000006 R11: 0000000000000005 R12: 0000000000000000
[ 2.713047] R13: ffffffff81c10480 R14: 0000000000000000 R15: 0000000000000000
[ 2.713048] </IRQ>
[ 2.713050] default_idle+0x1e/0x100
[ 2.713052] arch_cpu_idle+0xf/0x20
[ 2.713053] default_idle_call+0x2c/0x40
[ 2.713055] do_idle+0x158/0x1e0
[ 2.713056] cpu_startup_entry+0x73/0x80
[ 2.713058] rest_init+0xb8/0xc0
[ 2.713070] start_kernel+0x4a2/0x4c3
[ 2.713072] ? set_init_arg+0x5a/0x5a
[ 2.713074] ? early_idt_handler_array+0x120/0x120
[ 2.713075] x86_64_start_reservations+0x2a/0x2c
[ 2.713077] x86_64_start_kernel+0x14c/0x16f
[ 2.713079] secondary_startup_64+0x9f/0x9f
[ 2.713080] Code: 44 3b 35 1e 6f d0 00 7c 26 48 83 c4 10 5b 41 5c
41 5d 41 5e 41 5f 5d c3 8b 05 63 38 fc 00 85 c0 75 be 80 3d 20 0d d0
00 00 75 b5 <0f> ff eb b1 48 c7 c2 20 23 e2 81 4c 89 fe 44 89 f7 e8 20
b5 62
[ 2.713105] ---[ end trace 4d101d4c176c16b0 ]---

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