linux-kernel - Re: [syzbot ci] Re: KVM: x86: Unify L1TF flushing under per-CPU variable

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Message-ID: <DDHX5G54GS7D.1YC8514SPRGQF@google.com>
Date: Tue, 14 Oct 2025 08:57:32 +0000
From: Brendan Jackman <jackmanb@...gle.com>
To: syzbot ci <syzbot+ci693402a94575bcb2@...kaller.appspotmail.com>, <bp@...en8.de>, 
	<dave.hansen@...ux.intel.com>, <hpa@...or.com>, <jackmanb@...gle.com>, 
	<kvm@...r.kernel.org>, <linux-kernel@...r.kernel.org>, <mingo@...hat.com>, 
	<pbonzini@...hat.com>, <seanjc@...gle.com>, <tglx@...utronix.de>, 
	<x86@...nel.org>
Cc: <syzbot@...ts.linux.dev>, <syzkaller-bugs@...glegroups.com>
Subject: Re: [syzbot ci] Re: KVM: x86: Unify L1TF flushing under per-CPU variable

On Tue Oct 14, 2025 at 6:13 AM UTC, syzbot ci wrote:
> BUG: using __this_cpu_write() in preemptible code in x86_emulate_instruction

Ah. And now I realise I never booted my debug config on an actual
Skylake host, I'd better do that, presumably running the KVM selftests
with DEBUG_PREEMPT etc would have been enough to catch this earlier.

Anyway, I guest we just want to use vcpu->arch.last_vmentry_cpu instead
of smp_processor_id()?