From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from linux.microsoft.com (linux.microsoft.com [13.77.154.182]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 5DAA7200114; Wed, 12 Feb 2025 23:01:38 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=13.77.154.182 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1739401299; cv=none; b=FNLyyKL/Fy2slENE7T2pInPSX8FGEmbmJjWc1wwV9T7rnwXI5+drYkVGyBZvWfFQv4353ECFl705ZGfbFeGX8dSPoCG3qyqx47p8FRBHrGrkxCxF3yUaivTgGlyiD26kOuOtunHT9IiURG1QPWSCRWPJ0vEJlJUCrcTEzs0/34I= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1739401299; c=relaxed/simple; bh=rtbIGAaTmhLmf9KN3tRsPE4qOAzIjQbhJr1m74rRhwg=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=ev1w0C3VKjKKLbsB2Jj5YpneKtUHL9ba2U2F2bTmav00xGzQnUmZBRq59l26sDJliXpkiU+/rNl4oa0Kd+aV6+SvpnSLn10Bu+SoztPXNRyjDazHwKIkwe1eIMdQhBDmIIPs/OL2hucGfQ3m0OS9+KQqhvi4VqNXhicR0gYCqbo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.microsoft.com; spf=pass smtp.mailfrom=linux.microsoft.com; dkim=pass (1024-bit key) header.d=linux.microsoft.com header.i=@linux.microsoft.com header.b=U08z9jK9; arc=none smtp.client-ip=13.77.154.182 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.microsoft.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.microsoft.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.microsoft.com header.i=@linux.microsoft.com header.b="U08z9jK9" Received: from [10.0.0.114] (c-67-182-156-199.hsd1.wa.comcast.net [67.182.156.199]) by linux.microsoft.com (Postfix) with ESMTPSA id 63C73203F3F9; Wed, 12 Feb 2025 15:01:37 -0800 (PST) DKIM-Filter: OpenDKIM Filter v2.11.0 linux.microsoft.com 63C73203F3F9 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.microsoft.com; s=default; t=1739401297; bh=kVD/TzWf8xNmuKwiACtI1JZzyEv978UeZM6dCbKDUxQ=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=U08z9jK9iAY0zzo79A7JsC/Mz2ZbWBnrHFM5KY0O7MHmTpEOGkvA8SJUPe2B3lRVa jvX1WzrD4fslrZg15JInATk0D9kx25QMttWTdsm0IK1VZtYMIGPhwhJNJuJAgX25PJ Kv5P4xmlJC1vHp70JcBwBMfZWe2qmtpArPf05eG8= Message-ID: Date: Wed, 12 Feb 2025 15:01:36 -0800 Precedence: bulk X-Mailing-List: linux-arch@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] hyperv: Add CONFIG_MSHV_ROOT to gate hv_root_partition checks To: Easwar Hariharan Cc: linux-hyperv@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, iommu@lists.linux.dev, kys@microsoft.com, haiyangz@microsoft.com, wei.liu@kernel.org, mhklinux@outlook.com, decui@microsoft.com, catalin.marinas@arm.com, will@kernel.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com, daniel.lezcano@linaro.org, joro@8bytes.org, robin.murphy@arm.com, arnd@arndb.de, jinankjain@linux.microsoft.com, muminulrussell@gmail.com, skinsburskii@linux.microsoft.com, mukeshrathor@microsoft.com References: <1739312515-18848-1-git-send-email-nunodasneves@linux.microsoft.com> <20ba4b7c-bebb-4b1f-8c6c-4cd52a5083b5@linux.microsoft.com> Content-Language: en-US From: Nuno Das Neves In-Reply-To: <20ba4b7c-bebb-4b1f-8c6c-4cd52a5083b5@linux.microsoft.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 2/11/2025 9:47 PM, Easwar Hariharan wrote: > On 2/11/2025 2:21 PM, Nuno Das Neves wrote: >> Introduce CONFIG_MSHV_ROOT as a tristate to enable root partition >> booting and future mshv driver functionality. >> >> Change hv_root_partition into a function which always returns false >> if CONFIG_MSHV_ROOT=n. >> >> Introduce hv_current_partition_type to store the type of partition >> (guest, root, or other kinds in future), and hv_identify_partition_type() >> to it up early in Hyper-V initialization. > > ...to *set* it up early? > Yep! Thanks for catching that >> >> Signed-off-by: Nuno Das Neves >> --- >> Depends on >> https://lore.kernel.org/linux-hyperv/1738955002-20821-3-git-send-email-nunodasneves@linux.microsoft.com/ >> >> arch/arm64/hyperv/mshyperv.c | 2 ++ >> arch/x86/hyperv/hv_init.c | 10 ++++---- >> arch/x86/kernel/cpu/mshyperv.c | 24 ++---------------- >> drivers/clocksource/hyperv_timer.c | 4 +-- >> drivers/hv/Kconfig | 12 +++++++++ >> drivers/hv/Makefile | 3 ++- >> drivers/hv/hv.c | 10 ++++---- >> drivers/hv/hv_common.c | 32 +++++++++++++++++++----- >> drivers/hv/vmbus_drv.c | 2 +- >> drivers/iommu/hyperv-iommu.c | 4 +-- >> include/asm-generic/mshyperv.h | 39 +++++++++++++++++++++++++----- >> 11 files changed, 92 insertions(+), 50 deletions(-) >> > > > >> + >> +void hv_identify_partition_type(void) >> +{ >> + /* >> + * Check partition creation and cpu management privileges >> + * >> + * Hyper-V should never specify running as root and as a Confidential >> + * VM. But to protect against a compromised/malicious Hyper-V trying >> + * to exploit root behavior to expose Confidential VM memory, ignore >> + * the root partition setting if also a Confidential VM. >> + */ >> + if ((ms_hyperv.priv_high & HV_CREATE_PARTITIONS) && >> + (ms_hyperv.priv_high & HV_CPU_MANAGEMENT) && >> + !(ms_hyperv.priv_high & HV_ISOLATION)) { >> + hv_current_partition_type = HV_PARTITION_TYPE_ROOT; >> + pr_info("Hyper-V: running as root partition\n"); >> + } else { >> + hv_current_partition_type = HV_PARTITION_TYPE_GUEST; >> + } >> +} > > This should assume GUEST as default and modify to ROOT if all the checks pass. > It is doing that, isn't it? In fact the 'else' branch here is redundant and just there for additional clarity. hv_current_partition_type is zeroed (so GUEST) by default, but I could make that explicit if you prefer: +enum hv_partition_type hv_current_partition_type = HV_PARTITION_TYPE_GUEST; How does that sound? Am I misunderstanding something here? > > >> +static inline int hv_call_deposit_pages(int node, u64 partition_id, u32 num_pages) >> +{ >> + return hv_result(U64_MAX); >> +} > > Is there value in perhaps #defining hv_result_ as U64_MAX and returning that for documentation? > For e.g. assuming this is something like EOPNOTSUPP > > #define HV_RESULT_NOT_SUPP U64_MAX > > static inline int hv_call_deposit_pages(int node, u64 partition_id, u32 num_pages) > { return hv_result(HV_RESULT_NOT_SUPP); } > The idea here was to copy what hv_do_hypercall does returning U64_MAX in case the hypercall page is missing, which will hv_result() into an invalid status code. A special value for that status could make this pattern clearer. I'd want to call out that this isn't a "real" Hyper-V status code somehow. HV_STATUS's are 16 bits, so it would look more like: /* "LINUX" because this isn't really a status from the hypervisor.. */ #define HV_STATUS_LINUX_FAIL 0xFFFF static inline int hv_call_deposit_pages(int node, u64 partition_id, u32 num_pages) { return HV_STATUS_LINUX_FAIL; } Another option: there is another patch coming (which you know of) which maps hypercall status codes to regular Linux errors like -EOPNOTSUPP. I could simply merge that patch with this one (or make this a series for v2), and that would result in less churn. (And leave alone the current use of U64_MAX in hv_do_hypercall, for now). Nuno > > > Thanks, > Easwar (he/him)