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 93E1A1D7E4B; Thu, 19 Dec 2024 20:04:40 +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=1734638681; cv=none; b=q/lgzCk4VmcYXbIWBapcP9VYsQywUPt/8giTOy+1e2OUB2SJuWE9QW+sadRPzq7Efg1vc7scDzH6UiwAJ+MaFZEe6yCSPk6ECEIGcA0gIPr4X9RzUy4b3Xfh0+Pr/l3uyuBXdSmppEXeNB2nx5Rmc+zYhCSNTqerbNpYuMzk3pU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1734638681; c=relaxed/simple; bh=xBXQ7oRFRUjL97Av8ZtKmzVooj9NSPkzr2LLMSLbvwg=; h=Message-ID:Date:MIME-Version:Cc:Subject:To:References:From: In-Reply-To:Content-Type; b=O52l9v1ljlDPhcdBNMQfT+hNHdctDnO6xBPVNU2Lpfmzrb9THMpvl/uY/VlNB7cjPQ+NC5buoJSfc13e7UYDADMRcMY1vE7x1W4Al1bo/KwRu8HQhY4YsBv/QIfLG+DSewx6wOCSEjqTaRzrg2oFiWnzWbIsGcW2qt0yguLONSY= 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=dOuE8MP9; 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="dOuE8MP9" Received: from [100.65.65.151] (unknown [20.236.11.29]) by linux.microsoft.com (Postfix) with ESMTPSA id 85F34203FC97; Thu, 19 Dec 2024 12:04:39 -0800 (PST) DKIM-Filter: OpenDKIM Filter v2.11.0 linux.microsoft.com 85F34203FC97 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.microsoft.com; s=default; t=1734638680; bh=ZAnYdkUEgGhiJscwoFCTocatAA/2m/Y7+3vOoEmG45I=; h=Date:Cc:Subject:To:References:From:In-Reply-To:From; b=dOuE8MP9AuQjOVc7RdLOGe7rC3angkjjjs5uVUKs/oWLv3+3uh9L3zEwvEOg1OhsP OSqQKwuYn7+RQtZA9IHv7eVrJGI6hoYr70yXTkkZUHHjFsmS2Pu7/Uv5fond9M9tLu o7NtiUrtuaa7NRt7lOap55FnyRcdL83Ueqx9pebg= Message-ID: <4716c74c-d798-4c34-8c64-a8de4d0a6b45@linux.microsoft.com> Date: Thu, 19 Dec 2024 12:04:39 -0800 Precedence: bulk X-Mailing-List: linux-hyperv@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Cc: Nuno Das Neves , eahariha@linux.microsoft.com, hpa@zytor.com, kys@microsoft.com, bp@alien8.de, dave.hansen@linux.intel.com, decui@microsoft.com, haiyangz@microsoft.com, mingo@redhat.com, mhklinux@outlook.com, tglx@linutronix.de, tiala@microsoft.com, wei.liu@kernel.org, linux-hyperv@vger.kernel.org, linux-kernel@vger.kernel.org, x86@kernel.org, apais@microsoft.com, benhill@microsoft.com, ssengar@microsoft.com, sunilmut@microsoft.com, vdso@hexbites.dev Subject: Re: [PATCH 1/2] hyperv: Fix pointer type for the output of the hypercall in get_vtl(void) To: Roman Kisel References: <20241218205421.319969-1-romank@linux.microsoft.com> <20241218205421.319969-2-romank@linux.microsoft.com> <17f81f98-a7ca-45e0-87be-9f1cfa5c5a95@linux.microsoft.com> <48d3a3e0-8e2f-4eb8-b725-b6eed37c290c@linux.microsoft.com> <07820167-b415-40b0-9858-d25325c348ba@linux.microsoft.com> From: Easwar Hariharan Content-Language: en-US In-Reply-To: <07820167-b415-40b0-9858-d25325c348ba@linux.microsoft.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 12/19/2024 12:00 PM, Roman Kisel wrote: > > > On 12/19/2024 11:13 AM, Easwar Hariharan wrote: >> On 12/19/2024 10:40 AM, Nuno Das Neves wrote: >>> On 12/18/2024 12:54 PM, Roman Kisel wrote: >>>> Commit bc905fa8b633 ("hyperv: Switch from hyperv-tlfs.h to hyperv/ >>>> hvhdk.h") >>>> changed the type of the output pointer to `struct hv_register_assoc` >>>> from >>>> `struct hv_get_vp_registers_output`. That leads to an incorrect >>>> computation, >>>> and leaves the system broken. >>>> >>> My bad! But, lets not use `struct hv_get_registers_output`. Instead, use >>> `struct hv_register_value`, since that is the more complete >>> definition of a >>> register value. The output of the get_vp_registers hypercall is just >>> an array >>> of these values. >>> >>> Ideally we remove `struct hv_get_vp_registers_output` at some point, >>> since >>> it serves the same role as `struct hv_register_value` but in a more >>> limited >>> capacity. >>> >>> Thanks >>> Nuno >>> >> >> I had much the same conversation with Roman off-list yesterday. > Appreciate your help, Easwar! > >> >> The choice is between using hv_get_registers_output which is clearly the >> output of the GetVpRegisters hypercall by name, albeit limited as you >> said, and hv_register_value which is the more complete definition and >> what the hypervisor actually returns, but does not currently include the >> arm64 definitions in our copy of hvgdk_mini.h. hv_get_registers_output >> and hv_register_value overlap in layout for Roman's purposes. >> >> FWIW, I'm in favor of adding the arm64 definitions to hv_register_value >> and using it for this get_vtl() patch. > I could do that, will wait to see if no objections. > >> >> This could be accompanied with migration of hv_get_vpreg128 in arm64/ >> and removal of struct hv_get_registers_output, or that could be deferred >> to a later patch. > Having an equivalent of `hv_get_vpreg128` would be awesome on x64! > I'd bet something like that should exist in dom0/mshv already if you'd > like to have a dedicated function. So perhaps we could let mshv take > the lead with that? > > If the desire is also to use the fast hypercall technique as > `hv_get_vpreg128` does, then we'd need fast hypercalls on x64 that > can use XMM registers (aka the fast extended hypercalls) that aren't > implemented in the hyperv drivers from my read of the code (although > it seems KVM knows how to do that when it emulates Hyper-V, > arch/x86/kvm/hyperv.c, struct kvm_hv_hcall *hc). > > These considerations make me lean towards deferring hv_get_vpreg128-like > implementation to a later time. > To clarify, I didn't mean to include implementing extended fast hypercalls with the XMM registers, or an implementation of hv_get_vpreg128() for x64 in my suggestion. Just to fix up the existing hv_get_vpreg128 in arch/arm64 to use hv_register_value (or its Linux-specific helper as Nuno suggested). Thanks, Easwar