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 53567C4332F for ; Mon, 13 Nov 2023 03:38:02 +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-Type: Content-Transfer-Encoding:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id: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=EILaDRR34iOS3Uewed3oE6fZpRS0Z79wYKVvmr0mZAo=; b=DQVrE5L0+MklNr 38qCrUof57jKj3T+J5Ja/iwSAzuixhg5/aJA/apXG3mTut6HVufttRu4PWgT63TojHGnLDqosWwKX Q3WjIcdcc5HRXYXbCQa1yODDY2zKJY895seK/r3FrZbpiaM6DGlxkl2dyenAzXruzc3gvpmQWlpHb 6p9Kbpzczwl5Es7xPlVXTg5wvByQ7ehfRm9xItKEdiNq84f/7LFnrpQ7RgdOv9YgbDE6qN1gIklx8 pqI8ZUEBWkJu3yzFO5jFqoSAwSNf37ZKtVWRZOywy0VlYgufU23+6tE7L5wECGMtBc85mXF0bvn8Q SnzXO5YxB4QM+GgYCvTg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.96 #2 (Red Hat Linux)) id 1r2NlV-00D8oy-2o; Mon, 13 Nov 2023 03:37:33 +0000 Received: from mgamail.intel.com ([192.55.52.88]) by bombadil.infradead.org with esmtps (Exim 4.96 #2 (Red Hat Linux)) id 1r2NlR-00D8mu-0p; Mon, 13 Nov 2023 03:37:30 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1699846649; x=1731382649; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=Y+d5ffj+cXty8WEYU0vUgR9r7fyajtAWyyGi3xYe0Go=; b=OvC2Q5UYyVbg/SjcbJazgPKEcGKhOLPvaEOop6OMGXY8j0+BWLukP0CN HK70OKicVk9XsoeyDX25xzz8Z+GfPBW9aPEHOe6crUzKBMoO7G7LZvUiy p5mao9yhJp/JGxzdq2fFkCD1NyhkJfgf9+LaXXzvpPMqiKEuxpREhIoXQ lTzHJNn1EXCO9qf6C6SwOaUd2xruDiOUr89rWlJZoRffblYOQeg8r/DDt rbS7CJGo5qaKDhafA26lpcFiBhqFGfqZK5+OEXlq+wT8V1PN8vscF5X3W AiRJeCaipOyAWvhpFTp61uAVCfxEL7//grc3m92OzW5Hi1bpGf2LIDZp7 Q==; X-IronPort-AV: E=McAfee;i="6600,9927,10892"; a="421469899" X-IronPort-AV: E=Sophos;i="6.03,298,1694761200"; d="scan'208";a="421469899" Received: from orsmga002.jf.intel.com ([10.7.209.21]) by fmsmga101.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 12 Nov 2023 19:37:22 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6600,9927,10892"; a="764228152" X-IronPort-AV: E=Sophos;i="6.03,298,1694761200"; d="scan'208";a="764228152" Received: from xiaoyaol-hp-g830.ccr.corp.intel.com (HELO [10.93.6.77]) ([10.93.6.77]) by orsmga002-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 12 Nov 2023 19:37:09 -0800 Message-ID: Date: Mon, 13 Nov 2023 11:37:05 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 15/34] KVM: Add KVM_CREATE_GUEST_MEMFD ioctl() for guest-specific backing memory To: Sean Christopherson Cc: Paolo Bonzini , Marc Zyngier , Oliver Upton , Huacai Chen , Michael Ellerman , Anup Patel , Paul Walmsley , Palmer Dabbelt , Albert Ou , Alexander Viro , Christian Brauner , "Matthew Wilcox (Oracle)" , Andrew Morton , kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, linux-mips@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, kvm-riscv@lists.infradead.org, linux-riscv@lists.infradead.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Xu Yilun , Chao Peng , Fuad Tabba , Jarkko Sakkinen , Anish Moorthy , David Matlack , Yu Zhang , Isaku Yamahata , =?UTF-8?B?TWlja2HDq2wgU2FsYcO8?= =?UTF-8?Q?n?= , Vlastimil Babka , Vishal Annapurve , Ackerley Tng , Maciej Szmigiero , David Hildenbrand , Quentin Perret , Michael Roth , Wang , Liam Merwick , Isaku Yamahata , "Kirill A. Shutemov" References: <20231105163040.14904-1-pbonzini@redhat.com> <20231105163040.14904-16-pbonzini@redhat.com> <956d8ee3-8b63-4a2d-b0c4-c0d3d74a0f6f@intel.com> Content-Language: en-US From: Xiaoyao Li In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20231112_193729_308785_1F7A1415 X-CRM114-Status: GOOD ( 21.02 ) 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: , Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 11/11/2023 2:22 AM, Sean Christopherson wrote: > On Fri, Nov 10, 2023, Xiaoyao Li wrote: >> On 11/6/2023 12:30 AM, Paolo Bonzini wrote: >>> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h >>> index 68a144cb7dbc..a6de526c0426 100644 >>> --- a/include/linux/kvm_host.h >>> +++ b/include/linux/kvm_host.h >>> @@ -589,8 +589,20 @@ struct kvm_memory_slot { >>> u32 flags; >>> short id; >>> u16 as_id; >>> + >>> +#ifdef CONFIG_KVM_PRIVATE_MEM >>> + struct { >>> + struct file __rcu *file; >>> + pgoff_t pgoff; >>> + } gmem; >>> +#endif >>> }; >>> +static inline bool kvm_slot_can_be_private(const struct kvm_memory_slot *slot) >>> +{ >>> + return slot && (slot->flags & KVM_MEM_GUEST_MEMFD); >>> +} >>> + >> >> maybe we can move this block and ... >> >> >> >>> @@ -2355,6 +2379,30 @@ bool kvm_arch_pre_set_memory_attributes(struct kvm *kvm, >>> struct kvm_gfn_range *range); >>> bool kvm_arch_post_set_memory_attributes(struct kvm *kvm, >>> struct kvm_gfn_range *range); >>> + >>> +static inline bool kvm_mem_is_private(struct kvm *kvm, gfn_t gfn) >>> +{ >>> + return IS_ENABLED(CONFIG_KVM_PRIVATE_MEM) && >>> + kvm_get_memory_attributes(kvm, gfn) & KVM_MEMORY_ATTRIBUTE_PRIVATE; >>> +} >>> +#else >>> +static inline bool kvm_mem_is_private(struct kvm *kvm, gfn_t gfn) >>> +{ >>> + return false; >>> +} >>> #endif /* CONFIG_KVM_GENERIC_MEMORY_ATTRIBUTES */ >> >> this block to Patch 18? > > It would work, but my vote is to keep them here to minimize the changes to common > KVM code in the x86 enabling. It's not a strong preference though. Of course, > at this point, fiddling with this sort of thing is probably a bad idea in terms > of landing guest_memfd. Indeed. It's OK then. >>> @@ -4844,6 +4875,10 @@ static int kvm_vm_ioctl_check_extension_generic(struct kvm *kvm, long arg) >>> #ifdef CONFIG_KVM_GENERIC_MEMORY_ATTRIBUTES >>> case KVM_CAP_MEMORY_ATTRIBUTES: >>> return kvm_supported_mem_attributes(kvm); >>> +#endif >>> +#ifdef CONFIG_KVM_PRIVATE_MEM >>> + case KVM_CAP_GUEST_MEMFD: >>> + return !kvm || kvm_arch_has_private_mem(kvm); >>> #endif >>> default: >>> break; >>> @@ -5277,6 +5312,18 @@ static long kvm_vm_ioctl(struct file *filp, >>> case KVM_GET_STATS_FD: >>> r = kvm_vm_ioctl_get_stats_fd(kvm); >>> break; >>> +#ifdef CONFIG_KVM_PRIVATE_MEM >>> + case KVM_CREATE_GUEST_MEMFD: { >>> + struct kvm_create_guest_memfd guest_memfd; >> >> Do we need a guard of below? >> >> r = -EINVAL; >> if (!kvm_arch_has_private_mem(kvm)) >> goto out; > > Argh, yeah, that's weird since KVM_CAP_GUEST_MEMFD says "not supported" if the > VM doesn't support private memory. > > Enforcing that would break guest_memfd_test.c though. And having to create a > "special" VM just to test basic guest_memfd functionality would be quite > annoying. > > So my vote is to do: > > case KVM_CAP_GUEST_MEMFD: > return IS_ENABLED(CONFIG_KVM_PRIVATE_MEM); I'm fine with it. > There's no harm to KVM if userspace creates a file it can't use, and at some > point KVM will hopefully support guest_memfd irrespective of private memory. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel