x86/apic: Fix atomic update of offset in reserve_eilvt_offset()

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[ Upstream commit f96fb2df3e ]

The detection of atomic update failure in reserve_eilvt_offset() is
not correct. The value returned by atomic_cmpxchg() should be compared
to the old value from the location to be updated.

If these two are the same, then atomic update succeeded and
"eilvt_offsets[offset]" location is updated to "new" in an atomic way.

Otherwise, the atomic update failed and it should be retried with the
value from "eilvt_offsets[offset]" - exactly what atomic_try_cmpxchg()
does in a correct and more optimal way.

Fixes: a68c439b19 ("apic, x86: Check if EILVT APIC registers are available (AMD only)")
Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20230227160917.107820-1-ubizjak@gmail.com
Signed-off-by: Sasha Levin <sashal@kernel.org>

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Uros Bizjak 2023-02-27 17:09:17 +01:00 • committed by Greg Kroah-Hartman

parent 849ab4cf18

commit 7eaa457d1e

1 changed files with 2 additions and 3 deletions

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arch/x86/kernel/apic/apic.c

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