From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mta0.migadu.com (out-198.mta0.migadu.com [91.218.175.198]) (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 F0C334446FA for ; Mon, 14 Sep 2026 11:35:10 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.198 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789385713; cv=none; b=VYbd0FWAX9luxdn9cUOHBFeKZ4bCSHlVIJl8SU9rVLD/0mNfZP6wqV6xDb0jAg9JX+ZfqEg+tXx17QwCgkqdGhrSnleQf2iLw9HkKOTVjyKpgngDOxpd/xJNqHc99laq8q86pehWJRgSNWhF50zl4B4Ys5qprqbKpJ2rIOnGQhQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789385713; c=relaxed/simple; bh=4yfN1gycnb44ryNru42szUE7VLGbmxLWNo36QO1dLZM=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=XBtr1dYpdfLigqLC01vbmf9pImYfVK8toZuYwi/ojVlZLBixgNLB5ZYu8YMt8at3blTspnmkjO28DQvIBLBEeBd0cDQpLC6djoOnkG+/JDyaji52mpQlUpmxopi/v1dcf7rxhugWV+34M5M4pLRfH5vwLMVemHEED4H0lJKgLEw= 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=gjkZ6rxV; arc=none smtp.client-ip=91.218.175.198 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="gjkZ6rxV" X-Envelope-To: kvmarm@lists.linux.dev DKIM-Signature: a=rsa-sha256; bh=4yfN1gycnb44ryNru42szUE7VLGbmxLWNo36QO1dLZM=; c=simple/simple; d=linux.dev; h=from:to:subject:date:message-id:mime-version:content-type; s=key1; t=1789385708; v=1; x=1789990508; b=gjkZ6rxVwPc4dZsS6IlTqMu+GVZgGNucNQ8ouddgZYqH2UyTUiaM0b+t8TzxmIQQ15w5Fmo7 jlGDbQK07Zu3TtNlIO/tSLXojI9BzovwM6fDX+sUiW5cy6/IGRPMy5DnMMNQ+y9ElYLxDn4vs0Y MrrZLmHdij/y8bfwmVFR0kK8= X-Envelope-To: kvmarm@lists.linux.dev Received: by smtp.migadu.com with ESMTPS id bc666f73e4b472fb; Mon, 14 Sep 2026 11:35:08 +0000 X-Mizu-Trace-ID: bc666f73e4b472fb X-Migadu-Flow: FLOW_OUT From: Fuad Tabba To: maz@kernel.org, oupton@kernel.org, kvmarm@lists.linux.dev, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Cc: catalin.marinas@arm.com, will@kernel.org, joey.gouly@arm.com, seiden@linux.ibm.com, suzuki.poulose@arm.com, yuzenghui@huawei.com, mark.rutland@arm.com, steven.price@arm.com, vdonnefort@google.com, qperret@google.com, tabba@google.com Subject: [PATCH v3 12/18] KVM: arm64: Prevent host PC adjustments for protected vCPUs Date: Mon, 14 Sep 2026 12:33:32 +0100 Message-Id: <20260914113338.159227-13-fuad.tabba@linux.dev> X-Mailer: git-send-email 2.39.5 In-Reply-To: <20260914113338.159227-1-fuad.tabba@linux.dev> References: <20260914113338.159227-1-fuad.tabba@linux.dev> Precedence: bulk X-Mailing-List: kvmarm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit __kvm_adjust_pc() lets the host advance a vCPU's PC or inject an exception, which for a protected vCPU would let the host redirect guest execution. Drop the request there: the entry handlers apply the host's PC_UPDATE_REQ on re-entry, where EL2 allows it. __kvm_adjust_pc() adjusts the vCPU a get/put pair returns, the one it was given outside pKVM. Both host callers hold the vCPU mutex, so a hyp vCPU loaded for the vCPU is loaded on the calling CPU. The request for a loaded protected vCPU is dropped. For a loaded non-protected vCPU, PKVM_HOST_STATE_DIRTY selects the copy, since adjusting the hyp vCPU while the host copy is authoritative loses the update at the next flush. Adjusting the hyp vCPU copies PC_UPDATE_REQ in and back out again: without the copy back, INCREMENT_PC outlives the adjustment and the next KVM_SET_VCPU_EVENTS trips WARN_ON(INCREMENT_PC) in kvm_pend_exception(). With no hyp vCPU loaded, as under KVM_SET_VCPU_EVENTS, the host copy is adjusted as before. Until the marshalling patch clears PC_UPDATE_REQ on the host copy at exit, a KVM_RUN that returns to userspace with INCREMENT_PC set leaves it on the host copy of a loaded protected vCPU, and a KVM_SET_VCPU_EVENTS before the next run then trips that WARN_ON. Suggested-by: Marc Zyngier Signed-off-by: Fuad Tabba --- arch/arm64/kvm/hyp/exception.c | 21 +++++++++----- arch/arm64/kvm/hyp/include/hyp/adjust_pc.h | 19 +++++++++++++ arch/arm64/kvm/hyp/nvhe/hyp-main.c | 32 ++++++++++++++++++++++ 3 files changed, 65 insertions(+), 7 deletions(-) diff --git a/arch/arm64/kvm/hyp/exception.c b/arch/arm64/kvm/hyp/exception.c index 6e60d890afa4a..7ea62e5304ae9 100644 --- a/arch/arm64/kvm/hyp/exception.c +++ b/arch/arm64/kvm/hyp/exception.c @@ -353,12 +353,19 @@ static void kvm_inject_exception(struct kvm_vcpu *vcpu) */ void __kvm_adjust_pc(struct kvm_vcpu *vcpu) { - if (vcpu_get_flag(vcpu, PENDING_EXCEPTION)) { - kvm_inject_exception(vcpu); - vcpu_clear_flag(vcpu, PENDING_EXCEPTION); - vcpu_clear_flag(vcpu, EXCEPT_MASK); - } else if (vcpu_get_flag(vcpu, INCREMENT_PC)) { - kvm_skip_instr(vcpu); - vcpu_clear_flag(vcpu, INCREMENT_PC); + struct kvm_vcpu *target = pkvm_adjust_pc_get(vcpu); + + if (!target) + return; + + if (vcpu_get_flag(target, PENDING_EXCEPTION)) { + kvm_inject_exception(target); + vcpu_clear_flag(target, PENDING_EXCEPTION); + vcpu_clear_flag(target, EXCEPT_MASK); + } else if (vcpu_get_flag(target, INCREMENT_PC)) { + kvm_skip_instr(target); + vcpu_clear_flag(target, INCREMENT_PC); } + + pkvm_adjust_pc_put(vcpu, target); } diff --git a/arch/arm64/kvm/hyp/include/hyp/adjust_pc.h b/arch/arm64/kvm/hyp/include/hyp/adjust_pc.h index a4fb04faa7d09..94ba768996032 100644 --- a/arch/arm64/kvm/hyp/include/hyp/adjust_pc.h +++ b/arch/arm64/kvm/hyp/include/hyp/adjust_pc.h @@ -68,4 +68,23 @@ static inline void kvm_skip_host_instr(void) write_sysreg_el2(read_sysreg_el2(SYS_ELR) + 4, SYS_ELR); } +/* + * Under pKVM, the vCPU __kvm_adjust_pc() adjusts for @vcpu (NULL drops the + * request), and the copy of the consumed PC_UPDATE_REQ back to @vcpu. + */ +#ifdef __KVM_NVHE_HYPERVISOR__ +struct kvm_vcpu *pkvm_adjust_pc_get(struct kvm_vcpu *vcpu); +void pkvm_adjust_pc_put(struct kvm_vcpu *vcpu, struct kvm_vcpu *target); +#else +static inline struct kvm_vcpu *pkvm_adjust_pc_get(struct kvm_vcpu *vcpu) +{ + return vcpu; +} + +static inline void pkvm_adjust_pc_put(struct kvm_vcpu *vcpu, + struct kvm_vcpu *target) +{ +} +#endif + #endif diff --git a/arch/arm64/kvm/hyp/nvhe/hyp-main.c b/arch/arm64/kvm/hyp/nvhe/hyp-main.c index da8ab636063cf..1dcc75261dc08 100644 --- a/arch/arm64/kvm/hyp/nvhe/hyp-main.c +++ b/arch/arm64/kvm/hyp/nvhe/hyp-main.c @@ -642,6 +642,38 @@ static void handle___pkvm_host_mkyoung_guest(struct kvm_cpu_context *host_ctxt) cpu_reg(host_ctxt, 1) = ret; } +/* + * PKVM_HOST_STATE_DIRTY names the authoritative copy, the host's when set. + * A loaded protected vCPU takes the request at its next entry instead. + */ +struct kvm_vcpu *pkvm_adjust_pc_get(struct kvm_vcpu *vcpu) +{ + struct pkvm_hyp_vcpu *hyp_vcpu; + + if (!is_protected_kvm_enabled()) + return vcpu; + + hyp_vcpu = pkvm_get_loaded_hyp_vcpu(); + if (!hyp_vcpu || hyp_vcpu->host_vcpu != vcpu) + return vcpu; + + if (pkvm_hyp_vcpu_is_protected(hyp_vcpu)) + return NULL; + + if (vcpu_get_flag(vcpu, PKVM_HOST_STATE_DIRTY)) + return vcpu; + + vcpu_copy_flag(&hyp_vcpu->vcpu, vcpu, PC_UPDATE_REQ); + return &hyp_vcpu->vcpu; +} + +/* Reflect the consumed request back, otherwise it stays pending. */ +void pkvm_adjust_pc_put(struct kvm_vcpu *vcpu, struct kvm_vcpu *target) +{ + if (target != vcpu) + vcpu_copy_flag(vcpu, target, PC_UPDATE_REQ); +} + static void handle___kvm_adjust_pc(struct kvm_cpu_context *host_ctxt) { DECLARE_REG(struct kvm_vcpu *, vcpu, host_ctxt, 1); -- 2.39.5