From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 2E7EA15C82 for ; Mon, 5 Dec 2022 19:21:50 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id A605AC433C1; Mon, 5 Dec 2022 19:21:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1670268110; bh=iCR9tVPFb3GyNrpEFTYZErPW4yeXucjC05FSy3ScDew=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=oZ/tmAhDkHfTE8UVBTZs9r6F78L5chCeh226hpj24q0Yvt3tlxLAKCggu4OEFk2Ae OxhZb1Q0T7208DXXHAdvd1g4o1lg7t/8AJJvlHMZpMx/d2TX3J2PyjKEqZilDBVRnB XMInCkRFh5+mFSQwHwLj2gtK9UjwzpQUWo6oCHwo= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, James Morse Subject: [PATCH 4.19 089/105] arm64: errata: Fix KVM Spectre-v2 mitigation selection for Cortex-A57/A72 Date: Mon, 5 Dec 2022 20:10:01 +0100 Message-Id: <20221205190806.142991249@linuxfoundation.org> X-Mailer: git-send-email 2.38.1 In-Reply-To: <20221205190803.124472741@linuxfoundation.org> References: <20221205190803.124472741@linuxfoundation.org> User-Agent: quilt/0.67 Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit From: James Morse Both the Spectre-v2 and Spectre-BHB mitigations involve running a sequence immediately after exiting a guest, before any branches. In the stable kernels these sequences are built by copying templates into an empty vector slot. For Spectre-BHB, Cortex-A57 and A72 require the branchy loop with k=8. If Spectre-v2 needs mitigating at the same time, a firmware call to EL3 is needed. The work EL3 does at this point is also enough to mitigate Spectre-BHB. When enabling the Spectre-BHB mitigation, spectre_bhb_enable_mitigation() should check if a slot has already been allocated for Spectre-v2, meaning no work is needed for Spectre-BHB. This check was missed in the earlier backport, add it. Fixes: c20d55174479 ("arm64: Mitigate spectre style branch history side channels") Signed-off-by: James Morse Signed-off-by: Greg Kroah-Hartman --- arch/arm64/kernel/cpu_errata.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) --- a/arch/arm64/kernel/cpu_errata.c +++ b/arch/arm64/kernel/cpu_errata.c @@ -1246,7 +1246,13 @@ void spectre_bhb_enable_mitigation(const } else if (spectre_bhb_loop_affected(SCOPE_LOCAL_CPU)) { switch (spectre_bhb_loop_affected(SCOPE_SYSTEM)) { case 8: - kvm_setup_bhb_slot(__spectre_bhb_loop_k8_start); + /* + * A57/A72-r0 will already have selected the + * spectre-indirect vector, which is sufficient + * for BHB too. + */ + if (!__this_cpu_read(bp_hardening_data.fn)) + kvm_setup_bhb_slot(__spectre_bhb_loop_k8_start); break; case 24: kvm_setup_bhb_slot(__spectre_bhb_loop_k24_start);