From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pj1-f74.google.com (mail-pj1-f74.google.com [209.85.216.74]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C875A153BD9 for ; Tue, 6 May 2025 23:48:02 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.216.74 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1746575284; cv=none; b=eMdNR0f4wiU22DdF9WbVqR0fy3Ds5KOgnMOYQuup0Zip7qmsE/BcZXdA98XYd78iiasiXnoI1P5UQ8jkKoO626xLweka63bHRo4VPh4sO6fbPh9vJQMzNeUkYK8Mt5pqDVAlXlXsqL9Sg9filzaJh50+6cZdhl7cpaR6RN+buSw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1746575284; c=relaxed/simple; bh=NzEAJGMGj67aqLOqPzD1WsJBqcysNCKrFhpDypZk/yY=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=bPdqlmPoWRFsHyF4Ev+F5cqMTElxq50yDTlDp9UQnJvDrL+t5TMG5gWrXuCry/d3L+qA883SDosJubpwrLpK+kT9vmw9eY5HWVHgc+BjLXk2aMBK/Tk5gpaNFKk8MCkDtlbg9e3wYTOWfHzReS0TSUNMMDDPxtdu8MU/Ul8Oe5w= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--seanjc.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=lX4GNA+h; arc=none smtp.client-ip=209.85.216.74 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--seanjc.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="lX4GNA+h" Received: by mail-pj1-f74.google.com with SMTP id 98e67ed59e1d1-306b590faaeso4444873a91.3 for ; Tue, 06 May 2025 16:48:02 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1746575282; x=1747180082; darn=lists.linux.dev; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=iGR21MUMyA/Iej7QErtZc8eyio+Dks1zWhBSbKI/rik=; b=lX4GNA+hDJxXEI1GMZmI5Vaf1WCXNGlPMhlLsiq1cqrGwMx3tMy6UDNhj1/6l+e2k8 iAuLUpr1dSUIXSjD4WvruDSJlv3HCEhrZ4m4yeE53rT7M+XiMn0rwim64vvbAuiTY0WP MjNKCCzRT3cXbnlATqXb3HO1vHj81M2T1SGDZa8UWI3p1uWh++WfYegPkbsTwkubiuwb Rv+SU2xzxdsZ87vV5cRSgUjxJKhDJ2NeUXpCN1qR2jXkBHc9i7tAoeP5m5v/s+Rm+6r/ sheSMQFJBufh/MehPzeF9unXFAfWLOa5m21mTx5VvivMU9SdLaIkgglW7+2GilxubIJo Anpg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1746575282; x=1747180082; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=iGR21MUMyA/Iej7QErtZc8eyio+Dks1zWhBSbKI/rik=; b=RbuKHcOTKiVAbteDFeOS1v/jaR+J2/FevqTODupCexh2ydtDUhlPvm8qFKX9qgMhPv 96PR7ODS/c3WW9kdH33Af+Oq6oJY/gskdO1/MC7vcaTOz/x4SwPSz7fSFGc2sz9KIZbr CGLWdLq1P+EYWdbEuJztJ1wU745lsmx5PZx44C0fUE/xu1sE8RtuVYoHvZxA/5McKZWS iGsVdj2Nctjt2cBnxjzJckH4xUkeGI9o0NHw9mJzhLzEk/8ePMZGg25O0N+Es3iZNllh /ImhIkZB9yhvQUS6MWsKzEfgX1Y7VaF+30YljFXtvzgTlpaKHTW1j9mxX0h2LA0EUOpa oy1g== X-Forwarded-Encrypted: i=1; AJvYcCUUSlG8scybBkPK8zSzS2G0kI9eAIZ1DLcxytWAbYRCE4TF+QwIyMosXhF+rs0tJolOKkF6aE4=@lists.linux.dev X-Gm-Message-State: AOJu0YyRj5Vj/qzcvsnwg/jciEk/r7mQRXrA04XPy28tNXaRxBt7rjgf iVM/BZP589dp9en+gfZXAQmdJEvQacWovxRfmfkbr/YpqsFmAEg2TWYHKPVJwsQ/F7ogZyo+AMQ NJQ== X-Google-Smtp-Source: AGHT+IEI4VPbZHYscktwEOVP6g5TZOKepWU/P1YF6Ndm56diDY5BXYXdB3X0UtnsxrDOZgtWBFkyQyHQxS4= X-Received: from pjbsr12.prod.google.com ([2002:a17:90b:4e8c:b0:30a:2095:204b]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a17:90b:3e84:b0:2ff:5357:1c7f with SMTP id 98e67ed59e1d1-30aac28b3bcmr1863522a91.30.1746575282052; Tue, 06 May 2025 16:48:02 -0700 (PDT) Date: Tue, 6 May 2025 16:48:00 -0700 In-Reply-To: <20250109204929.1106563-1-jthoughton@google.com> Precedence: bulk X-Mailing-List: kvmarm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20250109204929.1106563-1-jthoughton@google.com> Message-ID: Subject: Re: [PATCH v2 00/13] KVM: Introduce KVM Userfault From: Sean Christopherson To: James Houghton Cc: Paolo Bonzini , Jonathan Corbet , Marc Zyngier , Oliver Upton , Yan Zhao , Nikita Kalyazin , Anish Moorthy , Peter Gonda , Peter Xu , David Matlack , wei.w.wang@intel.com, kvm@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev Content-Type: text/plain; charset="us-ascii" On Thu, Jan 09, 2025, James Houghton wrote: > James Houghton (13): > KVM: Add KVM_MEM_USERFAULT memslot flag and bitmap > KVM: Add KVM_MEMORY_EXIT_FLAG_USERFAULT > KVM: Allow late setting of KVM_MEM_USERFAULT on guest_memfd memslot > KVM: Advertise KVM_CAP_USERFAULT in KVM_CHECK_EXTENSION Starting with some series-wide feedback, the granularity of these first few patches is too fine. I normally like to split things up, but honestly, this is such a small feature that I don't see much point in separating the uAPI from the infrastructure. To avoid cyclical dependencies between common KVM and arch code, we can do all the prep, but not fully enable+advertise support on any architecture until all targeted architectures are fully ready. In other words, I think we should squish these into one patch, minus this bit at the very end of the series (spoiler alert): diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index ce7bf5de6d72..0106d6d461a3 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -1545,6 +1545,9 @@ static int check_memory_region_flags(struct kvm *kvm, !(mem->flags & KVM_MEM_GUEST_MEMFD)) valid_flags |= KVM_MEM_READONLY; + if (IS_ENABLED(CONFIG_KVM_GENERIC_PAGE_FAULT)) + valid_flags |= KVM_MEM_USERFAULT; + if (mem->flags & ~valid_flags) return -EINVAL; @@ -4824,6 +4827,9 @@ static int kvm_vm_ioctl_check_extension_generic(struct kvm *kvm, long arg) case KVM_CAP_CHECK_EXTENSION_VM: case KVM_CAP_ENABLE_CAP_VM: case KVM_CAP_HALT_POLL: +#ifdef CONFIG_KVM_GENERIC_PAGE_FAULT + case KVM_CAP_USERFAULT: +#endif return 1; #ifdef CONFIG_KVM_MMIO case KVM_CAP_COALESCED_MMIO: