Messages in this thread Patch in this message | | | From | Uros Bizjak <> | Subject | [PATCH] x86/apic: Fix atomic update of offset in reserve_eilvt_offset | Date | Mon, 27 Feb 2023 17:09:17 +0100 |
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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: a68c439b1966c ("apic, x86: Check if EILVT APIC registers are available (AMD only)") Signed-off-by: Uros Bizjak <ubizjak@gmail.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@redhat.com> Cc: Borislav Petkov <bp@alien8.de> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: "H. Peter Anvin" <hpa@zytor.com> --- arch/x86/kernel/apic/apic.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-)
diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c index 20d9a604da7c..770557110051 100644 --- a/arch/x86/kernel/apic/apic.c +++ b/arch/x86/kernel/apic/apic.c @@ -422,10 +422,9 @@ static unsigned int reserve_eilvt_offset(int offset, unsigned int new) if (vector && !eilvt_entry_is_changeable(vector, new)) /* may not change if vectors are different */ return rsvd; - rsvd = atomic_cmpxchg(&eilvt_offsets[offset], rsvd, new); - } while (rsvd != new); + } while (!atomic_try_cmpxchg(&eilvt_offsets[offset], &rsvd, new)); - rsvd &= ~APIC_EILVT_MASKED; + rsvd = new & ~APIC_EILVT_MASKED; if (rsvd && rsvd != vector) pr_info("LVT offset %d assigned for vector 0x%02x\n", offset, rsvd); -- 2.39.2
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