From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pl1-f202.google.com (mail-pl1-f202.google.com [209.85.214.202]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 5B28419CD1B for ; Wed, 28 Jan 2026 01:34:36 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.214.202 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769564077; cv=none; b=ngyOTFlgobUFXGQm8IhI2OTKQxzZZvp+BIer4+mqbhyMrEYBbdtPnImqYznGSvL9WG1s+JgkBtjm4IaafmmlEc0h0rRP6wh5gmJ8YSFzjoVam5t638XvvJN38UXKXxMheEvOeMHRkehcsngD+bibmNKxlAPZFGHC4RYdNPBlgRQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769564077; c=relaxed/simple; bh=wd67Q8E7iEfUm452Gf4C1aKqkFtBYleXVqc6Md8EpjQ=; h=Date:Mime-Version:Message-ID:Subject:From:To:Cc:Content-Type; b=NLYxXAe350rTsWZeUv+QFe8XkwgResvs0uJYKlgSw2DmSuQn8wlgHHMS/gl2BHZSN1pNomXvgI8EbWukfrre7Y9GaKs5uMI/flxGbdPqYhvsK2MiBY9YwqH8gVjFE5GWP+nKJVXcfIzlm0q6EkfPWnll3BtyhPiqBIz3MCXyR+k= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--seanjc.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=lAP/77Qj; arc=none smtp.client-ip=209.85.214.202 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--seanjc.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="lAP/77Qj" Received: by mail-pl1-f202.google.com with SMTP id d9443c01a7336-2a08cbeb87eso63702165ad.3 for ; Tue, 27 Jan 2026 17:34:36 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1769564075; x=1770168875; darn=vger.kernel.org; h=cc:to:from:subject:message-id:mime-version:date:reply-to:from:to:cc :subject:date:message-id:reply-to; bh=rXzFCjFTGBb3gpweOqVYwB52bwIvtgPfUI0kePmSE6w=; b=lAP/77Qjug/GPiMO514camtKa9+mdJxrDTGO+O5qIAckxasg5pKFF68CpqQXrjaYvq DuL9l8aSHF1mrX3eUEPOpxWXHVe8Zgb0/Ol1eXCdmUcoutbr1vD7+ABeLG+l8JrxLA/3 kLLVkJs+xRfXUIR0QukyAg+ICb7A3ILjKgtHLTQLx1pHCIpDU9dx2ZxRPuKuczNdGI+u xx5toP1gyhUyWV1H4rH3i0AE8Xn+IJFOO0yOWxdeWDGmVOTC8Y5SAfHfDpT3ZIqR48TY mwWOg566gL9lzqeYU3B/Mlhn3BjG6G6Oa+muFdbtvIAq62+Q34yBtyadUliewP4oMpMd +fnQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1769564075; x=1770168875; h=cc:to:from:subject:message-id:mime-version:date:reply-to :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=rXzFCjFTGBb3gpweOqVYwB52bwIvtgPfUI0kePmSE6w=; b=QbveGbc2fQ7kAX3F/IspGldGIKwuvSskJMRsF0/Yr4m3vvYP5tBIifDUbDaAAXJklR BvEbNgOj/2y2FGvKMK+IKo3hErnL9j9hUzZNzRtXCxDd5nBezQM8RpGkY+Fevr2BRovJ vZAlyqNxLCom5gFRBWuJKRpi/XBBr7IqCqVeIFSDj1H9ZqIirkTqvV04cMBtzPz3RDz6 NdKaWMODrJTyt3uqpAnbCv++ydJQnDQ3/+RfR+wYAy/187fYfqacVAOIZ0c+t0DYOZxc PS31Emd0D62Lo1BOM/MlxL+Ta9COaqHy129VlIDHQuFBW6nHeDHSjQvo5n7mp2MuzJk9 39Yg== X-Forwarded-Encrypted: i=1; AJvYcCX8G6QSr/btpIh6BLQpGwH3bXh77MBiUmCPpeuOFCnd3m6MkB0wDEErl9BrvdoBQZgrItUWGWDwZgf9b7Y=@vger.kernel.org X-Gm-Message-State: AOJu0YylySTU/hCTdRUZFe24zkcr+jk+pEdYvlLq/RqZGBPpx9ayLj5S GwycF+MkOVb88iEYTRO7gPLZUzlqBUA2ZpTYnP4Cjb7qWEbljwk8WPs8vxkout3WJ6z8+wHTyML PU6KGUw== X-Received: from pgax20.prod.google.com ([2002:a05:6a02:2e54:b0:bd9:a349:94c0]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6a21:e8c:b0:352:7cc0:93b7 with SMTP id adf61e73a8af0-38ec640bbc3mr3516060637.40.1769564075555; Tue, 27 Jan 2026 17:34:35 -0800 (PST) Reply-To: Sean Christopherson Date: Tue, 27 Jan 2026 17:34:30 -0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 X-Mailer: git-send-email 2.52.0.457.g6b5491de43-goog Message-ID: <20260128013432.3250805-1-seanjc@google.com> Subject: [PATCH 0/2] KVM: x86: Plug an intra-guest Spectre v2 hole From: Sean Christopherson To: Sean Christopherson , Paolo Bonzini Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Yosry Ahmed , Jim Mattson , David Kaplan Content-Type: text/plain; charset="UTF-8" Fix a bug where KVM neglects to emit IBPB when a vCPU is migrated *back* to a previous pCPU, in which case a misbehaving task B in the guest can unduly infuence e.g. the BTB of task A in the guest (running in the same vCPU). FWIW, I've had the first patch sitting around for several months as a micro-optimization, but was never posted it as I wasn't 100% confident my analysis was correct. But it makes plugging this hole much easier, so here it is... Reviews most definitely welcome. Sean Christopherson (2): KVM: x86: Defer IBPBs for vCPU and nested transitions until core run loop KVM: x86: Emit IBPB on pCPU migration if IBPB is advertised to guest arch/x86/include/asm/kvm_host.h | 1 + arch/x86/kvm/x86.c | 20 +++++++++++++++++++- arch/x86/kvm/x86.h | 2 +- 3 files changed, 21 insertions(+), 2 deletions(-) base-commit: e81f7c908e1664233974b9f20beead78cde6343a -- 2.52.0.457.g6b5491de43-goog