From nobody Sat Apr 11 12:31:03 2026 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id D0E7BC4332F for ; Thu, 3 Nov 2022 13:05:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231527AbiKCNFj (ORCPT ); Thu, 3 Nov 2022 09:05:39 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42808 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231226AbiKCNFL (ORCPT ); Thu, 3 Nov 2022 09:05:11 -0400 Received: from linux.microsoft.com (linux.microsoft.com [13.77.154.182]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id F358417E32; Thu, 3 Nov 2022 06:04:17 -0700 (PDT) Received: from jinankjain-dranzer.zrrkmle5drku1h0apvxbr2u2ee.ix.internal.cloudapp.net (unknown [20.188.121.5]) by linux.microsoft.com (Postfix) with ESMTPSA id A0E09205DA2F; Thu, 3 Nov 2022 06:04:13 -0700 (PDT) DKIM-Filter: OpenDKIM Filter v2.11.0 linux.microsoft.com A0E09205DA2F DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.microsoft.com; s=default; t=1667480657; bh=HLgBEfqnfR/pSo3ZddLSeTCBJ4DSAnSoOy6+9I7tDbg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=tInIXzvZ5DLoKnJIuYBKNbwTa4rSOgbayfk53bVeJyTmK26j7jjfnGAuzBxv2YiR3 3bR2rI8U/yG2dnJxzMBLwr9g16xnc4PWetTLiDM7QG3jRbkJ74Y8vyLLuUnPG8a2Li Q6dVE3ZkxlJuz+jLcNIFgwtwwh1m1xPSVqTTNfPs= From: Jinank Jain To: jinankjain@microsoft.com Cc: kys@microsoft.com, haiyangz@microsoft.com, wei.liu@kernel.org, decui@microsoft.com, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com, arnd@arndb.de, peterz@infradead.org, jpoimboe@kernel.org, jinankjain@linux.microsoft.com, seanjc@google.com, kirill.shutemov@linux.intel.com, ak@linux.intel.com, sathyanarayanan.kuppuswamy@linux.intel.com, linux-hyperv@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, anrayabh@linux.microsoft.com, mikelley@microsoft.com Subject: [PATCH v3 1/5] x86/hyperv: Add support for detecting nested hypervisor Date: Thu, 3 Nov 2022 13:04:03 +0000 Message-Id: <285b15b90ac6f29ef8ab6b6ececeeef7d7c6f380.1667480257.git.jinankjain@linux.microsoft.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" When Linux runs as a root partition for Microsoft Hypervisor. It is possible to detect if it is running as nested hypervisor using hints exposed by mshv. While at it expose a new variable called hv_nested which can be used later for making decisions specific to nested use case. Signed-off-by: Jinank Jain Reviewed-by: --- arch/x86/include/asm/hyperv-tlfs.h | 3 +++ arch/x86/include/asm/mshyperv.h | 2 ++ arch/x86/kernel/cpu/mshyperv.c | 7 +++++++ drivers/hv/hv_common.c | 7 +++++-- 4 files changed, 17 insertions(+), 2 deletions(-) diff --git a/arch/x86/include/asm/hyperv-tlfs.h b/arch/x86/include/asm/hype= rv-tlfs.h index 3089ec352743..d9a611565859 100644 --- a/arch/x86/include/asm/hyperv-tlfs.h +++ b/arch/x86/include/asm/hyperv-tlfs.h @@ -114,6 +114,9 @@ /* Recommend using the newer ExProcessorMasks interface */ #define HV_X64_EX_PROCESSOR_MASKS_RECOMMENDED BIT(11) =20 +/* Indicates that the hypervisor is nested within a Hyper-V partition. */ +#define HV_X64_HYPERV_NESTED BIT(12) + /* Recommend using enlightened VMCS */ #define HV_X64_ENLIGHTENED_VMCS_RECOMMENDED BIT(14) =20 diff --git a/arch/x86/include/asm/mshyperv.h b/arch/x86/include/asm/mshyper= v.h index 61f0c206bff0..3c39923e5969 100644 --- a/arch/x86/include/asm/mshyperv.h +++ b/arch/x86/include/asm/mshyperv.h @@ -26,6 +26,8 @@ void hyperv_vector_handler(struct pt_regs *regs); #if IS_ENABLED(CONFIG_HYPERV) extern int hyperv_init_cpuhp; =20 +extern bool hv_nested; + extern void *hv_hypercall_pg; =20 extern u64 hv_current_partition_id; diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c index 831613959a92..9a4204139490 100644 --- a/arch/x86/kernel/cpu/mshyperv.c +++ b/arch/x86/kernel/cpu/mshyperv.c @@ -37,6 +37,8 @@ =20 /* Is Linux running as the root partition? */ bool hv_root_partition; +/* Is Linux running on nested Microsoft Hypervisor */ +bool hv_nested; struct ms_hyperv_info ms_hyperv; =20 #if IS_ENABLED(CONFIG_HYPERV) @@ -301,6 +303,11 @@ static void __init ms_hyperv_init_platform(void) pr_info("Hyper-V: running as root partition\n"); } =20 + if (ms_hyperv.hints & HV_X64_HYPERV_NESTED) { + hv_nested =3D true; + pr_info("Hyper-V: running on a nested hypervisor\n"); + } + /* * Extract host information. */ diff --git a/drivers/hv/hv_common.c b/drivers/hv/hv_common.c index ae68298c0dca..dcb336ce374f 100644 --- a/drivers/hv/hv_common.c +++ b/drivers/hv/hv_common.c @@ -25,8 +25,8 @@ #include =20 /* - * hv_root_partition and ms_hyperv are defined here with other Hyper-V - * specific globals so they are shared across all architectures and are + * hv_root_partition, ms_hyperv and hv_nested are defined here with other + * Hyper-V specific globals so they are shared across all architectures an= d are * built only when CONFIG_HYPERV is defined. But on x86, * ms_hyperv_init_platform() is built even when CONFIG_HYPERV is not * defined, and it uses these two variables. So mark them as __weak @@ -36,6 +36,9 @@ bool __weak hv_root_partition; EXPORT_SYMBOL_GPL(hv_root_partition); =20 +bool __weak hv_nested; +EXPORT_SYMBOL_GPL(hv_nested); + struct ms_hyperv_info __weak ms_hyperv; EXPORT_SYMBOL_GPL(ms_hyperv); =20 --=20 2.25.1