From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 110FD47140C; Wed, 22 Jul 2026 07:42:58 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784706179; cv=none; b=s/Y5zs6p8k1KzB6cHmV+wsqGkY1fnnIzkpcVejG3nJncOUS/H3pV1IPKGXyXxSaioalrV07LlNRoeUg4GFAHKiHODzvXQSXldH7cibGCpokzM7yhDBtheoaXg2q7No7jrK0h8xaXwPmPUUrjjlSF+bJB/iakoIuHrI7SAmI+sQA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784706179; c=relaxed/simple; bh=KWU70KX0tFQDCTwjw+AhlaY2OczDd8WZ7jdJiKpJv7w=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=k+ROB7O6b7znj5HJ+Txsxj1tu9ZS+2eW90H0Dz2lsC4km1envf+5q8A3ZRBnnEkKR5eFV7qul0LFEQkRvWYgj54XBu57z0W/cZXP12GC6UOJc+d3WTXTfyP2MD1K+kbNeM5GiX/dHuaCt6f/QWNgpIQklDce2QWipnRmhRs+fkQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=WejH/5Hi; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="WejH/5Hi" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 71DFF1F00ADE; Wed, 22 Jul 2026 07:42:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1784706177; bh=MJqhkCIE3M8tbIb7660VksyabSZHni+DFQYUe7gvf3A=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=WejH/5Hilz6maKALvEN4gyrkWQZyum1OeSyIkA92Y8VeWWzM3CKKPr1Xy41lKgynt odDjOyt4bTG05sKfXzuCHPUnQD+WMj7/PSxKo+5gqf9RM0iFmCL/jdGltqMLri4ELP fyHuLlIjpJgGclMt4EgRlpmEhNVuUoYXSGgUSXdSQ470/VCSUhu0nQ4/cWBQssLQeV xuNE5ro4doLB2QbhM3RrDntEl+UFR34OBLvzJAI4VtTBU0iTun8NqiFux0B0lAag1x mfLBRX/sZ7QXxWTiJXtRkN5yzWG8ktUYK2ZcO1R2Ds0EuFTeOZiSMZIhKqroBdHLOk 0wlhMcilML+SQ== Received: from sofa.misterjones.org ([185.219.108.64] helo=valley-girl.lan) by disco-boy.misterjones.org with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.98.2) (envelope-from ) id 1wmRbT-00000007VfN-3Lj8; Wed, 22 Jul 2026 07:42:55 +0000 From: Marc Zyngier To: kvmarm@lists.linux.dev, linux-arm-kernel@lists.infradead.org, kvm@vger.kernel.org Cc: Steffen Eiden , Joey Gouly , Suzuki K Poulose , Oliver Upton , Zenghui Yu , Yao Yuan , Wei-Lin Chang Subject: [PATCH v3 07/28] KVM: arm64: Don't evaluate HCR_EL2.NV nor HFGITR_EL2.ERET on ERET fast path Date: Wed, 22 Jul 2026 08:42:13 +0100 Message-ID: <20260722074234.3330999-8-maz@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260722074234.3330999-1-maz@kernel.org> References: <20260722074234.3330999-1-maz@kernel.org> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-SA-Exim-Connect-IP: 185.219.108.64 X-SA-Exim-Rcpt-To: kvmarm@lists.linux.dev, linux-arm-kernel@lists.infradead.org, kvm@vger.kernel.org, seiden@linux.ibm.com, joey.gouly@arm.com, suzuki.poulose@arm.com, oupton@kernel.org, yuzenghui@huawei.com, yaoyuan@linux.alibaba.com, weilin.chang@arm.com X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false We currently avoid using the ERET fast path if the guest has HCR_EL2.NV set. This is an odd check, as NV doesn't mean much if HCR_EL2.TGE==1. Similarly, evaluating HFGITR_EL2.ERET makes little sense, as this only applies to the nested context, while the ERET fast-path is purely for the benefit of L1. Replace these bizarre checks with is_nested_ctxt() which makes a lot more sense: if we are running an L2, the ERET trap must go to L1. Fixes: dd0717a998f77 ("KVM: arm64: nv: Fast-track 'InHost' exception returns") Signed-off-by: Marc Zyngier --- arch/arm64/kvm/hyp/vhe/switch.c | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-) diff --git a/arch/arm64/kvm/hyp/vhe/switch.c b/arch/arm64/kvm/hyp/vhe/switch.c index bbe9cebd3d9d5..684cebf23aa0e 100644 --- a/arch/arm64/kvm/hyp/vhe/switch.c +++ b/arch/arm64/kvm/hyp/vhe/switch.c @@ -344,13 +344,15 @@ static bool kvm_hyp_handle_eret(struct kvm_vcpu *vcpu, u64 *exit_code) * if this is a VHE guest hypervisor returning to its own * userspace, or the hypervisor performing a local exception * return. No need to save/restore registers, no need to - * switch S2 MMU. Just do the canonical ERET. + * switch S2 MMU. Just do the canonical ERET unless we are in + * nested context. * - * Unless the trap has to be forwarded further down the line, - * of course... + * Note that this is made possible because KVM itself never traps + * ERET when running an L2. The consequence is that any ERET trap is + * the result of HCR_EL2 or HFGITR_EL2 programming by L1 for its own + * guest, and the exception must be forwarded to L1. */ - if ((__vcpu_sys_reg(vcpu, HCR_EL2) & HCR_NV) || - (__vcpu_sys_reg(vcpu, HFGITR_EL2) & HFGITR_EL2_ERET)) + if (is_nested_ctxt(vcpu)) return false; spsr = read_sysreg_el1(SYS_SPSR); -- 2.47.3