Re: [PATCH v17 02/13] perf/x86, KVM: Prevent host debug register leak into guest OS on NMI
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From: Peter Zijlstra <peterz@infradead.org>
Date: 2026-09-23 09:16:02
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On Tue, Sep 22, 2026 at 01:25:07PM +0900, Masami Hiramatsu (Google) wrote:
quoted hunk ↗ jump to hunk
diff --git a/arch/x86/kernel/hw_breakpoint.c b/arch/x86/kernel/hw_breakpoint.c index f846c15f21ca..0473a5c95856 100644 --- a/arch/x86/kernel/hw_breakpoint.c +++ b/arch/x86/kernel/hw_breakpoint.c@@ -102,6 +102,9 @@ int arch_install_hw_breakpoint(struct perf_event *bp) lockdep_assert_irqs_disabled(); + if (perf_guest_in_guest())
That naming is hilariously bad :-)
quoted hunk ↗ jump to hunk
+ return -EBUSY; + for (i = 0; i < HBP_NUM; i++) { struct perf_event **slot = this_cpu_ptr(&bp_per_reg[i]);
Note how the other -EBUSY return is a WARN. Why is silently not doing anything not a WARN in this case? And I suppose this is KGDB again?