From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mta1.migadu.com (out-36.mta1.migadu.com [95.215.58.36]) (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 C614E4A014B for ; Mon, 31 Aug 2026 16:35:19 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.36 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788194121; cv=none; b=Kc4sErYN3Tfd3YkgqoZKmpaNPxb8onRzMrT6BOH5PmTLU3qpF1uTTFoKR3YYQxXlzRq406VSb8Y02Rm7XpH84MudVifrAxu6E0HEaSG/kChGaxphwONU7UXCxMAseguQt0wMQ8TxJnTfubaTueGTr5lkLbG1DoGgSzp2cuHEMXs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788194121; c=relaxed/simple; bh=aEC3gGbsmRPY1vFm8z4e4gHuRufq9N0KewFxzyMR6c0=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=U/t8I+9+UqN3lS/MARVXFaYBWvPsQyumgeEerfI3ACnWGkMarJ5CkKEjtgnEhxkmUBQJONAc/foiSeHvDVOS/NFrPyINVqHgUJ8BKGoREwvNWnRZV+RF2yday54H6Q4w9yID7YTq5bFVuCu5nzdJ5Shrg/KLdammGwF1FnRK5p0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=H6Fng3Qd; arc=none smtp.client-ip=95.215.58.36 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="H6Fng3Qd" X-Envelope-To: linux-kernel@vger.kernel.org DKIM-Signature: a=rsa-sha256; bh=aEC3gGbsmRPY1vFm8z4e4gHuRufq9N0KewFxzyMR6c0=; c=simple/simple; d=linux.dev; h=from:to:subject:date:message-id:mime-version:content-type; s=key1; t=1788194117; v=1; x=1788798917; b=H6Fng3Qd2ZEZaaZhTe316KqCKih86dtXejyfBsnrTZVJV/Oj++5xUGKtmP6ZGJ9kbT6VAb29 /26eeZqD1Dy13cYaoRPOwmC3Dp3PH633zSQOU+FuWeKoTGL+c/M2hwrYYaoIGZSdCD9TL0I7bcM Nw5LdGY/nfg6ZjmVz8KoyBbU= X-Envelope-To: linux-kernel@vger.kernel.org Received: by smtp.migadu.com with ESMTPS id d64d18f3558bf44a; Mon, 31 Aug 2026 16:35:17 +0000 X-Mizu-Trace-ID: d64d18f3558bf44a X-Migadu-Flow: FLOW_OUT From: Fuad Tabba To: Marc Zyngier , Oliver Upton , kvmarm@lists.linux.dev, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Cc: Catalin Marinas , Will Deacon , Joey Gouly , Steffen Eiden , Suzuki K Poulose , Zenghui Yu , Vincent Donnefort , Quentin Perret , Fuad Tabba Subject: [PATCH 16/17] KVM: arm64: Reject host power-on of a vCPU that EL2 holds powered off Date: Mon, 31 Aug 2026 17:34:20 +0100 Message-Id: <20260831163421.272420-17-fuad.tabba@linux.dev> X-Mailer: git-send-email 2.39.5 In-Reply-To: <20260831163421.272420-1-fuad.tabba@linux.dev> References: <20260831163421.272420-1-fuad.tabba@linux.dev> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit A protected vCPU's power state belongs to EL2, which changes it only on the guest's own PSCI calls. KVM_SET_MP_STATE(RUNNABLE) on a vCPU EL2 holds powered off changes the host's copy alone, and the guest's next CPU_ON of that vCPU then fails: mp_state is no longer STOPPED, so the host returns ALREADY_ON, which EL2 turns into INTERNAL_FAILURE. SUSPENDED has the same effect. Track at the host whether EL2 holds a protected vCPU powered off and return -EPERM for both writes in that state. STOPPED stays permitted, so a VMM can pause a vCPU, and RUNNABLE on a vCPU EL2 has powered on, so it can resume one. Signed-off-by: Fuad Tabba --- arch/arm64/include/asm/kvm_host.h | 2 ++ arch/arm64/kvm/arm.c | 20 ++++++++++++++++++++ arch/arm64/kvm/pkvm.c | 21 +++++++++++++++++---- arch/arm64/kvm/psci.c | 3 +++ 4 files changed, 42 insertions(+), 4 deletions(-) diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h index 78a4d387f9fd4..39788c4331260 100644 --- a/arch/arm64/include/asm/kvm_host.h +++ b/arch/arm64/include/asm/kvm_host.h @@ -922,6 +922,8 @@ struct kvm_vcpu_arch { /* vcpu power state */ struct kvm_mp_state mp_state; spinlock_t mp_state_lock; + /* EL2 holds the protected vCPU powered off. Under mp_state_lock. */ + bool pkvm_powered_off; /* Cache some mmu pages needed inside spinlock regions */ struct kvm_mmu_memory_cache mmu_page_cache; diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c index 8caacdd4de020..a96d01b2c5e86 100644 --- a/arch/arm64/kvm/arm.c +++ b/arch/arm64/kvm/arm.c @@ -777,9 +777,12 @@ static void __kvm_arm_vcpu_power_off(struct kvm_vcpu *vcpu) kvm_vcpu_kick(vcpu); } +/* The guest's own CPU_OFF: EL2 has already powered the vCPU off. */ void kvm_arm_vcpu_power_off(struct kvm_vcpu *vcpu) { spin_lock(&vcpu->arch.mp_state_lock); + if (kvm_vm_is_protected(vcpu->kvm)) + vcpu->arch.pkvm_powered_off = true; __kvm_arm_vcpu_power_off(vcpu); spin_unlock(&vcpu->arch.mp_state_lock); } @@ -801,6 +804,13 @@ static bool kvm_arm_vcpu_suspended(struct kvm_vcpu *vcpu) return READ_ONCE(vcpu->arch.mp_state.mp_state) == KVM_MP_STATE_SUSPENDED; } +/* Only the guest's CPU_ON may start a vCPU EL2 holds powered off. */ +static bool kvm_pkvm_vcpu_is_powered_off(struct kvm_vcpu *vcpu) +{ + return kvm_vm_is_protected(vcpu->kvm) && + vcpu->arch.pkvm_powered_off; +} + int kvm_arch_vcpu_ioctl_get_mpstate(struct kvm_vcpu *vcpu, struct kvm_mp_state *mp_state) { @@ -818,12 +828,22 @@ int kvm_arch_vcpu_ioctl_set_mpstate(struct kvm_vcpu *vcpu, switch (mp_state->mp_state) { case KVM_MP_STATE_RUNNABLE: + if (kvm_pkvm_vcpu_is_powered_off(vcpu)) { + ret = -EPERM; + break; + } + WRITE_ONCE(vcpu->arch.mp_state, *mp_state); break; case KVM_MP_STATE_STOPPED: __kvm_arm_vcpu_power_off(vcpu); break; case KVM_MP_STATE_SUSPENDED: + if (kvm_pkvm_vcpu_is_powered_off(vcpu)) { + ret = -EPERM; + break; + } + kvm_arm_vcpu_suspend(vcpu); break; default: diff --git a/arch/arm64/kvm/pkvm.c b/arch/arm64/kvm/pkvm.c index 8e4c6e4bec123..8ae974fec42ba 100644 --- a/arch/arm64/kvm/pkvm.c +++ b/arch/arm64/kvm/pkvm.c @@ -118,12 +118,25 @@ static int __pkvm_create_hyp_vcpu(struct kvm_vcpu *vcpu) return -ENOMEM; ret = kvm_call_hyp_nvhe(__pkvm_init_vcpu, handle, vcpu, hyp_vcpu); - if (!ret) - vcpu_set_flag(vcpu, VCPU_PKVM_FINALIZED); - else + if (ret) { free_pages_exact(hyp_vcpu, hyp_vcpu_sz); + return ret; + } - return ret; + /* + * Mirror EL2's seeding of power_state from mp_state. The hyp vCPU is + * published, so take mp_state_lock against kvm_psci_vcpu_on(). + */ + if (kvm_vm_is_protected(vcpu->kvm)) { + spin_lock(&vcpu->arch.mp_state_lock); + if (kvm_arm_vcpu_stopped(vcpu)) + vcpu->arch.pkvm_powered_off = true; + spin_unlock(&vcpu->arch.mp_state_lock); + } + + vcpu_set_flag(vcpu, VCPU_PKVM_FINALIZED); + + return 0; } /* diff --git a/arch/arm64/kvm/psci.c b/arch/arm64/kvm/psci.c index e3db84400d1f8..208289a08099f 100644 --- a/arch/arm64/kvm/psci.c +++ b/arch/arm64/kvm/psci.c @@ -94,6 +94,9 @@ static unsigned long kvm_psci_vcpu_on(struct kvm_vcpu *source_vcpu) */ smp_wmb(); + /* EL2 has committed the protected vCPU to ON_PENDING to get here. */ + vcpu->arch.pkvm_powered_off = false; + WRITE_ONCE(vcpu->arch.mp_state.mp_state, KVM_MP_STATE_RUNNABLE); kvm_vcpu_wake_up(vcpu); -- 2.39.5