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 1816F45005; Fri, 27 Dec 2024 18:31:56 +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=1735324318; cv=none; b=PGOVQslsgrcbN7vZ+6Rw1Row3Tyzr5XptcU26/tTo8s9inqP02PP6UCwJbUft503iWPtQlXrkvz8UoQhVggC0nifc+feCXLub1zysoW1tc4qVkE7hiUEM7BzLUEqD6AHhDBPpUbRnMHyaew2uQOGjqnYuZfFqFCiuLImteLDbhU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1735324318; c=relaxed/simple; bh=jcE9otWhGAwFaxjYnKUfFcuRP0iMf9kIBxaWzsgpnkU=; h=From:To:Cc:Subject:Date:Message-Id:MIME-Version; b=oBNR1RSfy5s0U0lYzNRJT3t6bkblAN3vRcl1kdtJiVbyKGoaQjcxOAckSLp19PrscDd9wXv2FBqtcZAEVEXmDoyXVAWKkrrB8yxsBC3zyK4KJzW2WWCpAnevv0Vvl+yh6TysngBnOhW22cpE3mT3ydcJiQtaWq89FX1q9bhdSiw= 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=fXr2VSoM; 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="fXr2VSoM" Received: from romank-3650.corp.microsoft.com (unknown [131.107.160.188]) by linux.microsoft.com (Postfix) with ESMTPSA id 6C9F3203EC38; Fri, 27 Dec 2024 10:31:56 -0800 (PST) DKIM-Filter: OpenDKIM Filter v2.11.0 linux.microsoft.com 6C9F3203EC38 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.microsoft.com; s=default; t=1735324316; bh=0rDjtXu452ENbhJwX+rH+a820zZGMOiGmY2+2innb2g=; h=From:To:Cc:Subject:Date:From; b=fXr2VSoM2jOBu+cJaW9zfbHyzv/rwPyKJQ18gyz4Izlpdu078zFNNVNOcKkJ7XJk1 LJXAcnugiU3Emoo9nxvFvW2CjwagplfbvGWt7LWg1GUmvxDeSBd4+/EBMtTSl5kl12 Qqa3DKxQDn+qSSMnfAUHs1NZmh4csV+UrtOSjyOg= From: Roman Kisel To: hpa@zytor.com, kys@microsoft.com, bp@alien8.de, dave.hansen@linux.intel.com, decui@microsoft.com, eahariha@linux.microsoft.com, haiyangz@microsoft.com, mingo@redhat.com, mhklinux@outlook.com, nunodasneves@linux.microsoft.com, tglx@linutronix.de, tiala@microsoft.com, wei.liu@kernel.org, linux-hyperv@vger.kernel.org, linux-kernel@vger.kernel.org, x86@kernel.org Cc: apais@microsoft.com, benhill@microsoft.com, ssengar@microsoft.com, sunilmut@microsoft.com, vdso@hexbites.dev Subject: [PATCH v4 0/5] hyperv: Fixes for get_vtl(), hv_vtl_apicid_to_vp_id() Date: Fri, 27 Dec 2024 10:31:50 -0800 Message-Id: <20241227183155.122827-1-romank@linux.microsoft.com> X-Mailer: git-send-email 2.34.1 Precedence: bulk X-Mailing-List: linux-hyperv@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit The get_vtl(void) function * has got one bug when the code started using a wrong pointer type after refactoring, and also * the both function in question don't adhere to the requirements of the Hypervisor Top-Level Funactional Specification[1, 2] as the code overlaps the input and output areas for a hypercall. The first issue leads to a wrong 100% reproducible computation due to reading a byte worth of data at a wrong offset. That in turn leads to using a nonsensical value ("fortunately", could catch it easily!) for the current VTL when initiating VMBus communications. As a repercussion from that, the system wouldn't boot. The fix is straightforward: use the correct pointer type. The second issue doesn't seem to lead to any reproducible breakage just yet. It is fixed with using the output hypercall pages allocated per-CPU, and that isn't the only or the most obvious choice so let me elaborate why that fix appears to be the best one in my opinion out of the options I could conceive of. The approach chosen for fixing the second issue makes two things shine through: * these functions just get a vCPU register, no special treatment needs to be involved, * VTLs and dom0 can and should share code as both exist to provide services to a guest(s), be that from within the partition or from outside of it. The projected benefits include replacing the functions in question with a future `hv_get_vp_registers` one shared between dom0 and VTLs to allow for a better test coverage. I have validated the fixes by booting the fixed kernel in VTL2 up using OpenVMM and OpenHCL[3, 4]. [1] https://learn.microsoft.com/en-us/virtualization/hyper-v-on-windows/tlfs/hypercall-interface [2] https://github.com/MicrosoftDocs/Virtualization-Documentation/tree/main/tlfs [3] https://openvmm.dev/guide/user_guide/openhcl.html [4] https://github.com/microsoft/OpenVMM [v4] - Wrapped DECLARE_FLEX_ARRAY into a struct and added one more member as the documentation requires, - Removed superfluous type coercion, - Fixed tags, - Rebased onto the latest hyperv-next branch. [v3]: https://lore.kernel.org/lkml/20241226213110.899497-1-romank@linux.microsoft.com/ - Added a fix for hv_vtl_apicid_to_vp_id(), - Split out the patch for enabling the hypercall output page, - Updated the title of the patch series, [v2]: https://lore.kernel.org/lkml/20241226203050.800524-1-romank@linux.microsoft.com/ - Used the suggestions to define an additional structure to improve code readability, - Split out the patch with that definition. [v1]: https://lore.kernel.org/lkml/20241218205421.319969-1-romank@linux.microsoft.com/ Roman Kisel (5): hyperv: Define struct hv_output_get_vp_registers hyperv: Fix pointer type in get_vtl(void) hyperv: Enable the hypercall output page for the VTL mode hyperv: Do not overlap the hvcall IO areas in get_vtl() hyperv: Do not overlap the hvcall IO areas in hv_vtl_apicid_to_vp_id() arch/x86/hyperv/hv_init.c | 6 ++-- arch/x86/hyperv/hv_vtl.c | 2 +- drivers/hv/hv_common.c | 6 ++-- include/hyperv/hvgdk_mini.h | 65 +++++++++++++++++++++++++++++++++++-- 4 files changed, 70 insertions(+), 9 deletions(-) base-commit: 26e1b813fcd02984b1cac5f3decdf4b0bb56fe02 -- 2.34.1