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1b6f7401e0
As the support for vcpu hotplug is on the road, I pick them up here as experimental to let user try cpu hotplug and virtio-mem on arm64. Fixes: #3280 Signed-off-by: Jianyong Wu <jianyong.wu@arm.com>
70 lines
2.5 KiB
Diff
70 lines
2.5 KiB
Diff
From e3a11f2f7ccb0dbbb8cf95944e89b34fd928107a Mon Sep 17 00:00:00 2001
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From: Jianyong Wu <jianyong.wu@arm.com>
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Date: Mon, 6 Dec 2021 10:52:37 +0800
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Subject: [PATCH 6/7] arm64/mm: avoid fixmap race condition when create pud
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mapping
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The 'fixmap' is a global resource and is used recursively by
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create pud mapping(), leading to a potential race condition in the
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presence of a concurrent call to alloc_init_pud():
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kernel_init thread virtio-mem workqueue thread
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================== ===========================
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alloc_init_pud(...) alloc_init_pud(...)
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pudp = pud_set_fixmap_offset(...) pudp = pud_set_fixmap_offset(...)
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READ_ONCE(*pudp)
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pud_clear_fixmap(...)
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READ_ONCE(*pudp) // CRASH!
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As kernel may sleep during creating pud mapping, introduce a mutex lock to
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serialise use of the fixmap entries by alloc_init_pud(). However, there is
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no need for locking in early boot stage and it doesn't work well with
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KASLR enabled when early boot. So, enable lock when system_state doesn't
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equal to "SYSTEM_BOOTING".
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Signed-off-by: Jianyong Wu <jianyong.wu@arm.com>
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Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
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Fixes: f4710445458c ("arm64: mm: use fixmap when creating page tables")
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Link: https://lore.kernel.org/r/20220201114400.56885-1-jianyong.wu@arm.com
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Signed-off-by: Will Deacon <will@kernel.org>
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---
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arch/arm64/mm/mmu.c | 7 +++++++
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1 file changed, 7 insertions(+)
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diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
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index cfd9deb347c3..432fab4ce2b4 100644
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--- a/arch/arm64/mm/mmu.c
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+++ b/arch/arm64/mm/mmu.c
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@@ -63,6 +63,7 @@ static pmd_t bm_pmd[PTRS_PER_PMD] __page_aligned_bss __maybe_unused;
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static pud_t bm_pud[PTRS_PER_PUD] __page_aligned_bss __maybe_unused;
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static DEFINE_SPINLOCK(swapper_pgdir_lock);
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+static DEFINE_SPINLOCK(fixmap_lock);
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void set_swapper_pgd(pgd_t *pgdp, pgd_t pgd)
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{
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@@ -328,6 +329,11 @@ static void alloc_init_pud(pgd_t *pgdp, unsigned long addr, unsigned long end,
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}
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BUG_ON(p4d_bad(p4d));
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+ /*
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+ * We only have one fixmap entry per page-table level, so take
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+ * the fixmap lock until we're done.
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+ */
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+ spin_lock(&fixmap_lock);
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pudp = pud_set_fixmap_offset(p4dp, addr);
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do {
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pud_t old_pud = READ_ONCE(*pudp);
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@@ -358,6 +364,7 @@ static void alloc_init_pud(pgd_t *pgdp, unsigned long addr, unsigned long end,
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} while (pudp++, addr = next, addr != end);
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pud_clear_fixmap();
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+ spin_unlock(&fixmap_lock);
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}
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static void __create_pgd_mapping(pgd_t *pgdir, phys_addr_t phys,
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--
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2.17.1
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