Commit a6d996cb authored Aug 13, 2020 by Sebastian Andrzej Siewior Committed by Thomas Gleixner Aug 13, 2020

x86/alternatives: Acquire pte lock with interrupts enabled



pte lock is never acquired in-IRQ context so it does not require interrupts
to be disabled. The lock is a regular spinlock which cannot be acquired
with interrupts disabled on RT.

RT complains about pte_lock() in __text_poke() because it's invoked after
disabling interrupts.

__text_poke() has to disable interrupts as use_temporary_mm() expects
interrupts to be off because it invokes switch_mm_irqs_off() and uses
per-CPU (current active mm) data.

Move the PTE lock handling outside the interrupt disabled region.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by; Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20200813105026.bvugytmsso6muljw@linutronix.de

parent f29dfa53

arch/x86/kernel/alternative.c

+3 −3

Original line number	Diff line number	Diff line
		@@ -874,8 +874,6 @@ static void __text_poke(void addr, const void *opcode, size_t len)
		*/
		BUG_ON(!pages[0] \|\| (cross_page_boundary && !pages[1]));

		local_irq_save(flags);

		/*
		* Map the page without the global bit, as TLB flushing is done with
		* flush_tlb_mm_range(), which is intended for non-global PTEs.
		@@ -892,6 +890,8 @@ static void __text_poke(void addr, const void *opcode, size_t len)
		*/
		VM_BUG_ON(!ptep);

		local_irq_save(flags);

		pte = mk_pte(pages[0], pgprot);
		set_pte_at(poking_mm, poking_addr, ptep, pte);

		@@ -941,8 +941,8 @@ static void __text_poke(void addr, const void *opcode, size_t len)
		*/
		BUG_ON(memcmp(addr, opcode, len));

		pte_unmap_unlock(ptep, ptl);
		local_irq_restore(flags);
		pte_unmap_unlock(ptep, ptl);
		return addr;
		}

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