powerpc/64s: Fix compiler store ordering to SLB shadow area (926bc2f1) · Commits · 戴 / test

The stores to update the SLB shadow area must be made as they appear in the C code, so that the hypervisor does not see an entry with mismatched vsid and esid. Use WRITE_ONCE for this. GCC has been observed to elide the first store to esid in the update, which means that if the hypervisor interrupts the guest after storing to vsid, it could see an entry with old esid and new vsid, which may possibly result in memory corruption. Signed-off-by:

Nicholas Piggin <npiggin@gmail.com> Signed-off-by:

Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/mm/slb.c

+4 −4

Original line number	Diff line number	Diff line
		@@ -63,14 +63,14 @@ static inline void slb_shadow_update(unsigned long ea, int ssize,
		* updating it. No write barriers are needed here, provided
		* we only update the current CPU's SLB shadow buffer.
		*/
		p->save_area[index].esid = 0;
		p->save_area[index].vsid = cpu_to_be64(mk_vsid_data(ea, ssize, flags));
		p->save_area[index].esid = cpu_to_be64(mk_esid_data(ea, ssize, index));
		WRITE_ONCE(p->save_area[index].esid, 0);
		WRITE_ONCE(p->save_area[index].vsid, cpu_to_be64(mk_vsid_data(ea, ssize, flags)));
		WRITE_ONCE(p->save_area[index].esid, cpu_to_be64(mk_esid_data(ea, ssize, index)));
		}

		static inline void slb_shadow_clear(enum slb_index index)
		{
		get_slb_shadow()->save_area[index].esid = 0;
		WRITE_ONCE(get_slb_shadow()->save_area[index].esid, 0);
		}

		static inline void create_shadowed_slbe(unsigned long ea, int ssize,

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