From mboxrd@z Thu Jan 1 00:00:00 1970 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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 0C8B3C3DA4A for ; Mon, 5 Aug 2024 15:17:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: Content-Type:In-Reply-To:From:References:Cc:To:Subject:MIME-Version:Date: Message-ID:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=6GyeyjDuXwHvma2YRErxRNnhO7eoDqcJzPc+sTV9L0s=; b=MahN0/qfhivG72LTzrCtLF/LVR lh91Z7FFV/kFdLEdQ8URGO6yHuOCcEhrwQ23ARTMUMtFiyAVNCYCQuhRyGfBstmzbvAcwqLKWmHA8 v5nyOl9+Sq4I36z6dpxpmQpjsi66BY4r1QsBjpNMHgvF/xPwk54/19KP6328pq/yDukKmf3kUS7MI 2aPWhIrNLwQWaJCpY6SzAodG4PUt4/Sav20S1srICLGZPVr4xL+k0McilV8QZb8yoH3ehl+sx9+vl p2Gh87JgdNKRt+D/gFmnp7dkqjun9nu9NVTitb5BOLd2nBvmlPf+b2Sk5c7zdZ9A/HYsfIW1NloG9 S0eYW5vQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.97.1 #2 (Red Hat Linux)) id 1sazSt-0000000GH6U-2OB9; Mon, 05 Aug 2024 15:17:39 +0000 Received: from linux.microsoft.com ([13.77.154.182]) by bombadil.infradead.org with esmtp (Exim 4.97.1 #2 (Red Hat Linux)) id 1sazSN-0000000GH0E-0ZPT for linux-arm-kernel@lists.infradead.org; Mon, 05 Aug 2024 15:17:08 +0000 Received: from [10.137.186.190] (unknown [131.107.159.62]) by linux.microsoft.com (Postfix) with ESMTPSA id 99C1F20B7165; Mon, 5 Aug 2024 08:17:05 -0700 (PDT) DKIM-Filter: OpenDKIM Filter v2.11.0 linux.microsoft.com 99C1F20B7165 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.microsoft.com; s=default; t=1722871025; bh=6GyeyjDuXwHvma2YRErxRNnhO7eoDqcJzPc+sTV9L0s=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=NMScHm3m1ft3fKhFfC97Fy5+DOwIdMfnd5Fo8itdR7iJGE5UTqk1/bsPfWeqQMWOj HbSZ8oWdCW3A9fUp8wFdiS4km8Pp8gEBZ31CAPGpCTxX3jol4QGvaNrcYYNHmhZ3Rp sPL2w7wxPYb2jxpxbTzDdILB8tUlbdbtLv1F6Pho= Message-ID: Date: Mon, 5 Aug 2024 08:17:05 -0700 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 1/7] arm64: hyperv: Use SMC to detect hypervisor presence To: Saurabh Singh Sengar Cc: arnd@arndb.de, bhelgaas@google.com, bp@alien8.de, catalin.marinas@arm.com, dave.hansen@linux.intel.com, decui@microsoft.com, haiyangz@microsoft.com, hpa@zytor.com, kw@linux.com, kys@microsoft.com, lenb@kernel.org, lpieralisi@kernel.org, mingo@redhat.com, rafael@kernel.org, robh@kernel.org, tglx@linutronix.de, wei.liu@kernel.org, will@kernel.org, linux-acpi@vger.kernel.org, linux-arch@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-hyperv@vger.kernel.org, linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org, x86@kernel.org, apais@microsoft.com, benhill@microsoft.com, ssengar@microsoft.com, sunilmut@microsoft.com, vdso@hexbites.dev References: <20240726225910.1912537-1-romank@linux.microsoft.com> <20240726225910.1912537-2-romank@linux.microsoft.com> <20240805035340.GA13276@linuxonhyperv3.guj3yctzbm1etfxqx2vob5hsef.xx.internal.cloudapp.net> Content-Language: en-US From: Roman Kisel In-Reply-To: <20240805035340.GA13276@linuxonhyperv3.guj3yctzbm1etfxqx2vob5hsef.xx.internal.cloudapp.net> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240805_081707_375582_31AF19DB X-CRM114-Status: GOOD ( 24.66 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 8/4/2024 8:53 PM, Saurabh Singh Sengar wrote: > On Fri, Jul 26, 2024 at 03:59:04PM -0700, Roman Kisel wrote: >> The arm64 Hyper-V startup path relies on ACPI to detect >> running under a Hyper-V compatible hypervisor. That >> doesn't work on non-ACPI systems. >> >> Hoist the ACPI detection logic into a separate function, >> use the new SMC added recently to Hyper-V to use in the >> non-ACPI case. >> >> Signed-off-by: Roman Kisel >> --- >> arch/arm64/hyperv/mshyperv.c | 36 ++++++++++++++++++++++++++----- >> arch/arm64/include/asm/mshyperv.h | 5 +++++ >> 2 files changed, 36 insertions(+), 5 deletions(-) >> >> diff --git a/arch/arm64/hyperv/mshyperv.c b/arch/arm64/hyperv/mshyperv.c >> index b1a4de4eee29..341f98312667 100644 >> --- a/arch/arm64/hyperv/mshyperv.c >> +++ b/arch/arm64/hyperv/mshyperv.c >> @@ -27,6 +27,34 @@ int hv_get_hypervisor_version(union hv_hypervisor_version_info *info) >> return 0; >> } >> >> +static bool hyperv_detect_via_acpi(void) >> +{ >> + if (acpi_disabled) >> + return false; >> +#if IS_ENABLED(CONFIG_ACPI) >> + /* Hypervisor ID is only available in ACPI v6+. */ >> + if (acpi_gbl_FADT.header.revision < 6) >> + return false; >> + return strncmp((char *)&acpi_gbl_FADT.hypervisor_id, "MsHyperV", 8) == 0; >> +#else >> + return false; >> +#endif >> +} >> + >> +static bool hyperv_detect_via_smc(void) >> +{ >> + struct arm_smccc_res res = {}; >> + >> + if (arm_smccc_1_1_get_conduit() != SMCCC_CONDUIT_HVC) >> + return false; >> + arm_smccc_1_1_hvc(ARM_SMCCC_VENDOR_HYP_CALL_UID_FUNC_ID, &res); >> + >> + return res.a0 == ARM_SMCCC_VENDOR_HYP_UID_HYPERV_REG_0 && >> + res.a1 == ARM_SMCCC_VENDOR_HYP_UID_HYPERV_REG_1 && >> + res.a2 == ARM_SMCCC_VENDOR_HYP_UID_HYPERV_REG_2 && >> + res.a3 == ARM_SMCCC_VENDOR_HYP_UID_HYPERV_REG_3; >> +} > > As you mentioned in the cover letter this is supported in latest Hyper-V hypervisor, > can we add a comment about it, specifying the exact version in it would be great. > I can add a comment about that, thought that would look as too much detail to refer to a version of the Windows insiders build in the comments in this code. Another option would be to entrench the logic in if statements which felt gross as there is a fallback. > If someone attempts to build non-ACPI kernel on older Hyper-V what is the > behaviour of this function, do we need to safeguard or handle that case ? The function won't panic if that's what you're asking about, i.e. safe for runtime. That won't break the build either as it relies on the SMCCC spec, and that uses the smc or hvc instructions (the code does expect hvc to be the conduit and checks for that being the case). The hypervisor doesn't inject the exception in the guest for the unknown call, just returns SMCCC_RET_NOT_SUPPORTED in the first output register (the hypervisor got a unit-test for that, too). That said, I think the logic is solid. Appreciate your question and your help! Will be glad to discuss other concerns should you have any. > > - Saurabh -- Thank you, Roman