From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) (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 91EE5221541; Fri, 14 Feb 2025 11:34:53 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=193.142.43.55 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1739532895; cv=none; b=ppG0Wzpt+Kznpqm62ea8JKVJz6eg3YT7PNFSTkKF3kK6PXRbVDifWpUtmKFWgiDJuouxM/HrkeHKq/0UyA3eDRy+n2U0f0rSMr9Em9gLYctjppwptKpM3gl49q4aTFW3EOFkN6FageJ8Qst0H9VaDfUhSE6R99Ft6Z7/hj5TjB4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1739532895; c=relaxed/simple; bh=ZSR5ExLzPOWzKeKJCYti0FPwPXEtrgPIJBvFt7ageL8=; h=From:To:Cc:Subject:In-Reply-To:References:Date:Message-ID: MIME-Version:Content-Type; b=dwk8NZNh21ayng0IeDKlbnGLtHdZhpGKnFYRvgWmVng7EveNGoEebW5aZzcYEpF8vi01UTRuCpt+0wWcgnprHBBqjjjB49VQ+9cIZ1QpxsUrsIu5xlQXzEcnHDtufMXOYFB5VidtZlmKSiSTI/aeTKviUuYbxNeWRNFwh3Jz970= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de; spf=pass smtp.mailfrom=linutronix.de; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=0VNtTEYh; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=WFnwPIfj; arc=none smtp.client-ip=193.142.43.55 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linutronix.de Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="0VNtTEYh"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="WFnwPIfj" From: Thomas Gleixner DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1739532886; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=WWdSDqLPiHMtkC3qRBjEr7KgW5xesCDv6jmHPBIB4Zc=; b=0VNtTEYhNZqymGENVsUmuk+rnlFfX7RSGT3Ho51Jzxq38FSlmeIElqqU148QkLgRvvbxMF oARriYR4RFpth96NjMkBo5hNBkelucCuzn5JwatniL1M08uy4SKjyhCAdV/qdQ/eba99LI XiEfVSgYOnLLjTtprHlvawcrkXxeqR+m8TpQcRwp+J+sEstFenL0586F5ak1q3mLy7LV6n qnrektVapcPsyxUDFZn8atapF68IW+EhNarZoqS+FgcZ3nF1GslRp9zthgkNswbWYfqivE 2J78e9sNA7ZDPletmeb/HsB02wyQreu92A/Zp2E3TtpGj+8SwnWuzKOp2Uz71Q== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1739532886; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=WWdSDqLPiHMtkC3qRBjEr7KgW5xesCDv6jmHPBIB4Zc=; b=WFnwPIfjvhMmBrrfQwvQ/cPdgZnaXQkJD4fxKY5hU7USn1NEKaf7iB28bu/zo8sPSUnwBx KGOlqDpRoCYGNWAw== To: David Woodhouse , Thomas =?utf-8?Q?Wei=C3=9Fschuh?= , "James E.J. Bottomley" , Helge Deller , Andy Lutomirski , Vincenzo Frascino , Anna-Maria Behnsen , Frederic Weisbecker , Andrew Morton , Catalin Marinas , Will Deacon , Theodore Ts'o , "Jason A. Donenfeld" , Paul Walmsley , Palmer Dabbelt , Albert Ou , Huacai Chen , WANG Xuerui , Russell King , Heiko Carstens , Vasily Gorbik , Alexander Gordeev , Christian Borntraeger , Sven Schnelle , Thomas Bogendoerfer , Michael Ellerman , Nicholas Piggin , Christophe Leroy , Naveen N Rao , Madhavan Srinivasan , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Arnd Bergmann , Guo Ren Cc: linux-parisc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-riscv@lists.infradead.org, loongarch@lists.linux.dev, linux-s390@vger.kernel.org, linux-mips@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-arch@vger.kernel.org, Nam Cao , linux-csky@vger.kernel.org, "Ridoux, Julien" , "Luu, Ryan" , kvm Subject: Re: [PATCH v3 00/18] vDSO: Introduce generic data storage In-Reply-To: References: <20250204-vdso-store-rng-v3-0-13a4669dfc8c@linutronix.de> Date: Fri, 14 Feb 2025 12:34:44 +0100 Message-ID: <87ed00kbe3.ffs@tglx> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable David! On Thu, Feb 06 2025 at 09:31, David Woodhouse wrote: > Thanks for working on this. Is there a plan to expose the time data > directly to userspace in a form which is usable *other* than by > function calls which get the value of the clock at a given moment? > > For populating the vmclock device=C2=B9 we need to know the actual > relationship between the hardware counter (TSC, arch timer, etc.) and > real time in order to propagate that to the guest. > > I see two options for doing this: > > 1. Via userspace, exposing the vdso time data (and a notification when > it changes?) and letting the userspace VMM populate the vmclock. > This is complex for x86 because of TSC scaling; in fact userspace > doesn't currently know the precise scaling from host to guest TSC > so we'd have to be able to extract that from KVM. Exposing the raw data is not going to happen as we would create an ABI preventing any modifications to the internals. VDSO data is considered a fully internal (think kernel) representation and the accessor functions create an ABI around it. So if at all you can add a accessor function which exposes data to user space so that the internal data representation can still be modified as necessary. > 2. In kernel, asking KVM to populate the vmclock structure much like > it does other pvclocks shared with the guest. KVM/x86 already uses > pvclock_gtod_register_notifier() to hook changes; should we expand > on that? The problem with that notifier is that it seems to be > called far more frequently than I'd expect. It's called once per tick to expose the continous updates to the conversion factors and related internal data. Thanks, tglx 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 96480C02198 for ; Fri, 14 Feb 2025 11:49:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:Message-ID:Date:References :In-Reply-To:Subject:Cc:To:From:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=bunN1h8gbZzECje6bSMrYn/dWL//12Cd3rWhICdB3Zg=; b=fo3fjVYG5fCXEZ GD9KdlfBQa2Y037SWjtK3EQY/UOU1pswHojmShJeyLFZ5w/oJHH+9qs3sRyYdBmljk4wPrOoWKlgJ pgnUQYdEkmG8IQLf4uJT7jbZiI3424x16n88tHvOxkBarKuoGYrjJTteF6EJ24aETgX4emJ3TYPyg QhPMmkVsGJgI1Wkl1DWABIk29oQXE3oMl7oo9tYTIh7lEk1jOqRfKMH7Sk92JtUOXRUMJG9ZQhMR1 o+yR83XSbQYeSSYlWzIKwKBKeD6MRRCJR1vGS+rm2rwHOhm4c30O0Tgv06AmaDGqK+s1dmMuKLoTh AMQEf62LxVBALaohOEKQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98 #2 (Red Hat Linux)) id 1tiuBr-0000000EjoU-3wbl; Fri, 14 Feb 2025 11:49:03 +0000 Received: from galois.linutronix.de ([2a0a:51c0:0:12e:550::1]) by bombadil.infradead.org with esmtps (Exim 4.98 #2 (Red Hat Linux)) id 1tity6-0000000Eh5z-3zXl; Fri, 14 Feb 2025 11:34:52 +0000 From: Thomas Gleixner DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1739532886; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=WWdSDqLPiHMtkC3qRBjEr7KgW5xesCDv6jmHPBIB4Zc=; b=0VNtTEYhNZqymGENVsUmuk+rnlFfX7RSGT3Ho51Jzxq38FSlmeIElqqU148QkLgRvvbxMF oARriYR4RFpth96NjMkBo5hNBkelucCuzn5JwatniL1M08uy4SKjyhCAdV/qdQ/eba99LI XiEfVSgYOnLLjTtprHlvawcrkXxeqR+m8TpQcRwp+J+sEstFenL0586F5ak1q3mLy7LV6n qnrektVapcPsyxUDFZn8atapF68IW+EhNarZoqS+FgcZ3nF1GslRp9zthgkNswbWYfqivE 2J78e9sNA7ZDPletmeb/HsB02wyQreu92A/Zp2E3TtpGj+8SwnWuzKOp2Uz71Q== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1739532886; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=WWdSDqLPiHMtkC3qRBjEr7KgW5xesCDv6jmHPBIB4Zc=; b=WFnwPIfjvhMmBrrfQwvQ/cPdgZnaXQkJD4fxKY5hU7USn1NEKaf7iB28bu/zo8sPSUnwBx KGOlqDpRoCYGNWAw== To: David Woodhouse , Thomas =?utf-8?Q?Wei=C3=9Fschuh?= , "James E.J. Bottomley" , Helge Deller , Andy Lutomirski , Vincenzo Frascino , Anna-Maria Behnsen , Frederic Weisbecker , Andrew Morton , Catalin Marinas , Will Deacon , Theodore Ts'o , "Jason A. Donenfeld" , Paul Walmsley , Palmer Dabbelt , Albert Ou , Huacai Chen , WANG Xuerui , Russell King , Heiko Carstens , Vasily Gorbik , Alexander Gordeev , Christian Borntraeger , Sven Schnelle , Thomas Bogendoerfer , Michael Ellerman , Nicholas Piggin , Christophe Leroy , Naveen N Rao , Madhavan Srinivasan , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Arnd Bergmann , Guo Ren Cc: linux-parisc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-riscv@lists.infradead.org, loongarch@lists.linux.dev, linux-s390@vger.kernel.org, linux-mips@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-arch@vger.kernel.org, Nam Cao , linux-csky@vger.kernel.org, "Ridoux, Julien" , "Luu, Ryan" , kvm Subject: Re: [PATCH v3 00/18] vDSO: Introduce generic data storage In-Reply-To: References: <20250204-vdso-store-rng-v3-0-13a4669dfc8c@linutronix.de> Date: Fri, 14 Feb 2025 12:34:44 +0100 Message-ID: <87ed00kbe3.ffs@tglx> MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250214_033451_138757_97DC5281 X-CRM114-Status: GOOD ( 22.36 ) X-BeenThere: linux-riscv@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: base64 Sender: "linux-riscv" Errors-To: linux-riscv-bounces+linux-riscv=archiver.kernel.org@lists.infradead.org RGF2aWQhCgpPbiBUaHUsIEZlYiAwNiAyMDI1IGF0IDA5OjMxLCBEYXZpZCBXb29kaG91c2Ugd3Jv dGU6Cj4gVGhhbmtzIGZvciB3b3JraW5nIG9uIHRoaXMuIElzIHRoZXJlIGEgcGxhbiB0byBleHBv c2UgdGhlIHRpbWUgZGF0YQo+IGRpcmVjdGx5IHRvIHVzZXJzcGFjZSBpbiBhIGZvcm0gd2hpY2gg aXMgdXNhYmxlICpvdGhlciogdGhhbiBieQo+IGZ1bmN0aW9uIGNhbGxzIHdoaWNoIGdldCB0aGUg dmFsdWUgb2YgdGhlIGNsb2NrIGF0IGEgZ2l2ZW4gbW9tZW50Pwo+Cj4gRm9yIHBvcHVsYXRpbmcg dGhlIHZtY2xvY2sgZGV2aWNlwrkgd2UgbmVlZCB0byBrbm93IHRoZSBhY3R1YWwKPiByZWxhdGlv bnNoaXAgYmV0d2VlbiB0aGUgaGFyZHdhcmUgY291bnRlciAoVFNDLCBhcmNoIHRpbWVyLCBldGMu KSBhbmQKPiByZWFsIHRpbWUgaW4gb3JkZXIgdG8gcHJvcGFnYXRlIHRoYXQgdG8gdGhlIGd1ZXN0 Lgo+Cj4gSSBzZWUgdHdvIG9wdGlvbnMgZm9yIGRvaW5nIHRoaXM6Cj4KPiAgMS4gVmlhIHVzZXJz cGFjZSwgZXhwb3NpbmcgdGhlIHZkc28gdGltZSBkYXRhIChhbmQgYSBub3RpZmljYXRpb24gd2hl bgo+ICAgICBpdCBjaGFuZ2VzPykgYW5kIGxldHRpbmcgdGhlIHVzZXJzcGFjZSBWTU0gcG9wdWxh dGUgdGhlIHZtY2xvY2suCj4gICAgIFRoaXMgaXMgY29tcGxleCBmb3IgeDg2IGJlY2F1c2Ugb2Yg VFNDIHNjYWxpbmc7IGluIGZhY3QgdXNlcnNwYWNlCj4gICAgIGRvZXNuJ3QgY3VycmVudGx5IGtu b3cgdGhlIHByZWNpc2Ugc2NhbGluZyBmcm9tIGhvc3QgdG8gZ3Vlc3QgVFNDCj4gICAgIHNvIHdl J2QgaGF2ZSB0byBiZSBhYmxlIHRvIGV4dHJhY3QgdGhhdCBmcm9tIEtWTS4KCkV4cG9zaW5nIHRo ZSByYXcgZGF0YSBpcyBub3QgZ29pbmcgdG8gaGFwcGVuIGFzIHdlIHdvdWxkIGNyZWF0ZSBhbiBB QkkKcHJldmVudGluZyBhbnkgbW9kaWZpY2F0aW9ucyB0byB0aGUgaW50ZXJuYWxzLiBWRFNPIGRh dGEgaXMgY29uc2lkZXJlZCBhCmZ1bGx5IGludGVybmFsICh0aGluayBrZXJuZWwpIHJlcHJlc2Vu dGF0aW9uIGFuZCB0aGUgYWNjZXNzb3IgZnVuY3Rpb25zCmNyZWF0ZSBhbiBBQkkgYXJvdW5kIGl0 LiBTbyBpZiBhdCBhbGwgeW91IGNhbiBhZGQgYSBhY2Nlc3NvciBmdW5jdGlvbgp3aGljaCBleHBv c2VzIGRhdGEgdG8gdXNlciBzcGFjZSBzbyB0aGF0IHRoZSBpbnRlcm5hbCBkYXRhCnJlcHJlc2Vu dGF0aW9uIGNhbiBzdGlsbCBiZSBtb2RpZmllZCBhcyBuZWNlc3NhcnkuCgo+ICAyLiBJbiBrZXJu ZWwsIGFza2luZyBLVk0gdG8gcG9wdWxhdGUgdGhlIHZtY2xvY2sgc3RydWN0dXJlIG11Y2ggbGlr ZQo+ICAgICBpdCBkb2VzIG90aGVyIHB2Y2xvY2tzIHNoYXJlZCB3aXRoIHRoZSBndWVzdC4gS1ZN L3g4NiBhbHJlYWR5IHVzZXMKPiAgICAgcHZjbG9ja19ndG9kX3JlZ2lzdGVyX25vdGlmaWVyKCkg dG8gaG9vayBjaGFuZ2VzOyBzaG91bGQgd2UgZXhwYW5kCj4gICAgIG9uIHRoYXQ/IFRoZSBwcm9i bGVtIHdpdGggdGhhdCBub3RpZmllciBpcyB0aGF0IGl0IHNlZW1zIHRvIGJlCj4gICAgIGNhbGxl ZCBmYXIgbW9yZSBmcmVxdWVudGx5IHRoYW4gSSdkIGV4cGVjdC4KCkl0J3MgY2FsbGVkIG9uY2Ug cGVyIHRpY2sgdG8gZXhwb3NlIHRoZSBjb250aW5vdXMgdXBkYXRlcyB0byB0aGUKY29udmVyc2lv biBmYWN0b3JzIGFuZCByZWxhdGVkIGludGVybmFsIGRhdGEuCgpUaGFua3MsCgogICAgICAgIHRn bHgKCgpfX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fXwpsaW51 eC1yaXNjdiBtYWlsaW5nIGxpc3QKbGludXgtcmlzY3ZAbGlzdHMuaW5mcmFkZWFkLm9yZwpodHRw Oi8vbGlzdHMuaW5mcmFkZWFkLm9yZy9tYWlsbWFuL2xpc3RpbmZvL2xpbnV4LXJpc2N2Cg==