From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 39BD131E107; Tue, 23 Sep 2025 09:02:45 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=90.155.50.34 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1758618167; cv=none; b=HVKPd1kDm7+AR0a6TfFC89kd9ZZW5P0z5+YXUlLVNX14SqcCDzBC/K9bBa3meC6RdD0goqvaM5SuYQTg7vCsKBkoQF9jmRJKejlacFHNnETBQhvxIESxuxAhg751ORk89f6WV2gaM1qxSaNemTGwPUedKk64TPTyj4rd7Lu6Rms= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1758618167; c=relaxed/simple; bh=xCG2gh/6eIz4LGLdVw6yhC+2DHd4uGd1mcgzsf5psGM=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=EMiUwWy37AQlL4bZaMRs4A35ujqQzNRgg1445hyRppLbbxJACvrUC5g2BiXRcLivTzncrx//i9OInBtZkRLv/UzJ6nekmHhcXvaO+tXtTUxfNFYWfQpM9oul9EZXPghnm8Dh4HMvVA6praX/vZQmaAlIkRjmvW/MThk5c+hLWdA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org; spf=none smtp.mailfrom=casper.srs.infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=fcHt0z3h; arc=none smtp.client-ip=90.155.50.34 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=casper.srs.infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="fcHt0z3h" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=MIME-Version:Content-Type:References: In-Reply-To:Date:Cc:To:From:Subject:Message-ID:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=70TpCwFaIyGe3KXB6s+x31vUbM0ZIyshoHwXPvlt+4Q=; b=fcHt0z3hxZLI8uqmXlNwLg+6yz gOJONGttt1OQVb1ymLy6xqn2kLSauxQS1Mxkeq2gtNOqyo7CXxM+u9prOS6NajIUD2tsxTo9g/B/p kUDs25akAkjq+wOr/T0o4oK/mLKXSdTnrqlinrJKhnk2EaavgJqo35N7daLTmdmJtjdVbbeKnniuG N5FU6/TbAYchhRw8/6+aYVL7t06Ktv/9nnu7ZIG2W2KMAJJI1szGMQK0ZcI/R2A3aTQ5g1apMF7Mf 3DhQ4Ct85bHRkkeSsKWwiBbOxljNscDpiC1fbXkCn7aPVZmGNeP3BeoFz6C3Jqc7f1ZUTfxhroYP+ F/ca9nvQ==; Received: from [54.239.6.190] (helo=u09cd745991455d.ant.amazon.com) by casper.infradead.org with esmtpsa (Exim 4.98.2 #2 (Red Hat Linux)) id 1v0yv1-00000008YgD-2UmL; Tue, 23 Sep 2025 09:02:39 +0000 Message-ID: Subject: Re: [PATCH] KVM: arm64: Implement KVM_TRANSLATE ioctl for arm64 From: David Woodhouse To: Alexander Graf , Priscilla Lam , maz@kernel.org, oliver.upton@linux.dev Cc: christoffer.dall@arm.com, gurugubs@amazon.com, jgrall@amazon.co.uk, joey.gouly@arm.com, kvmarm@lists.linux.dev, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, suzuki.poulose@arm.com, yuzenghui@huawei.com Date: Tue, 23 Sep 2025 10:02:38 +0100 In-Reply-To: <97759f51-385b-4ce4-8766-d00ed5af580b@amazon.com> References: <86frcd1tp4.wl-maz@kernel.org> <20250923082955.66602-1-prl@amazon.com> <97759f51-385b-4ce4-8766-d00ed5af580b@amazon.com> Content-Type: multipart/signed; micalg="sha-256"; protocol="application/pkcs7-signature"; boundary="=-2+7Due4sKE215/2KPo3Z" User-Agent: Evolution 3.52.3-0ubuntu1 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-SRS-Rewrite: SMTP reverse-path rewritten from by casper.infradead.org. See http://www.infradead.org/rpr.html --=-2+7Due4sKE215/2KPo3Z Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Tue, 2025-09-23 at 10:39 +0200, Alexander Graf wrote: >=20 > All modern OSs constrain themselves to only ISV enabled MMIO=20 > instructions. Why? Such does not appear to be required by the architecture, AFAICT? And what is "MMIO" architecturally anyway? Using LDP is actually fine on MMIO, if a PCI BAR is passed through to a guest (and assuming there are no ordering dependencies on the loads). It's the fact that it's missing from stage2 page tables and causes a guest exit which is the problem. Other than lying to a compiler and *pretending* there are ordering constraints, or explicitly using inline asm, how would a guest OS *prevent* the compiler from using problematic instructions? > NISV is really only useful to run non hypervisor=20 > enlightened guests. Did you encounter a real world OS that was causing= =20 > NISV faults? And if so, what was causing these? It's most likely a=20 > driver or OS bug. The Windows CRB TPM driver uses LDP. Even if it *were* forbidden by the architecture, the track record of getting Microsoft to fix bugs *even* when they are egregious violations of both specifications and common sense is... poor. --=-2+7Due4sKE215/2KPo3Z Content-Type: application/pkcs7-signature; name="smime.p7s" Content-Disposition: attachment; filename="smime.p7s" Content-Transfer-Encoding: base64 MIAGCSqGSIb3DQEHAqCAMIACAQExDzANBglghkgBZQMEAgEFADCABgkqhkiG9w0BBwEAAKCCD9Aw ggSOMIIDdqADAgECAhAOmiw0ECVD4cWj5DqVrT9PMA0GCSqGSIb3DQEBCwUAMGUxCzAJBgNVBAYT AlVTMRUwEwYDVQQKEwxEaWdpQ2VydCBJbmMxGTAXBgNVBAsTEHd3dy5kaWdpY2VydC5jb20xJDAi BgNVBAMTG0RpZ2lDZXJ0IEFzc3VyZWQgSUQgUm9vdCBDQTAeFw0yNDAxMzAwMDAwMDBaFw0zMTEx MDkyMzU5NTlaMEExCzAJBgNVBAYTAkFVMRAwDgYDVQQKEwdWZXJva2V5MSAwHgYDVQQDExdWZXJv a2V5IFNlY3VyZSBFbWFpbCBHMjCCASIwDQYJKoZIhvcNAQEBBQADggEPADCCAQoCggEBAMjvgLKj jfhCFqxYyRiW8g3cNFAvltDbK5AzcOaR7yVzVGadr4YcCVxjKrEJOgi7WEOH8rUgCNB5cTD8N/Et GfZI+LGqSv0YtNa54T9D1AWJy08ZKkWvfGGIXN9UFAPMJ6OLLH/UUEgFa+7KlrEvMUupDFGnnR06 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