From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mgamail.intel.com (mgamail.intel.com [198.175.65.14]) (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 08D00489863; Mon, 3 Aug 2026 02:43:44 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.175.65.14 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785725028; cv=none; b=oFXVFkAL6Xom5BrLzI3+CN5M3hFJcTRVGq7iAQa0cWzkCVwxua+soySRtMJeXuG6HoRmf3sWbZz8A2s4gl5srIXltPSFRNSHJdi6FsS/cFcCeOQTGSIIS8qSCKe3CkIrf65VtkdZhHTsMbDRun1omeDdBOC6igtWOtuZCeWbzFc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785725028; c=relaxed/simple; bh=CFNSytE+2tg0bkqq7UMDHzkgq4F5EqtfTyEFf8TpgrM=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=sprt2HZY7CZF4+dHM+cusvgTi/fXUfUaLlkQr/wT/Mnt3K5DAfdufJU2XywUqd7YjuCmdjH7K+ppOjUCtqEy8wqI4557pkbKb4ajtEKOlf2SPzI4ip2A4Ad7PLag/BHWsWJRutyWldNXCVZMlZKucuzBPO69lJQINdThWhA9ZLQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=intel.com; spf=pass smtp.mailfrom=intel.com; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b=kFu8fuyU; arc=none smtp.client-ip=198.175.65.14 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=intel.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=intel.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b="kFu8fuyU" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1785725025; x=1817261025; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=CFNSytE+2tg0bkqq7UMDHzkgq4F5EqtfTyEFf8TpgrM=; b=kFu8fuyUivNfuv1b20Z/BgKD5WD0q3KZabkjyh8d8j7+1k2kH34NjNGr EQ7z4a3PmfHJvUUes4Nhwqy9ZxeMaKHiHG8pUhx12luooITjLr2XZETEW X8lg9UpVfwv0WyZmba8bv0MQ8SErvfAUAtLo9wZmDO/XjlP/afTYSpMhw vOdTQ5THt8yq12nd6xz5ZmJ0pg/R6cGdhr7Exu09/Je0SlywJrt+BAr9s mCCDsqLmDda5uOtPmtD+74ttxeVAEfSwSigijoou7ZdvzozvfOaepWH2i jqnL8+YY5sYr8yvvEqFhWar1Yy/LJ24tfHOl4l1KT1fY5vEWNz2iRP9Kw Q==; X-CSE-ConnectionGUID: qlLuhEv4Sbqog1+RZIQvTg== X-CSE-MsgGUID: c9q+uS57TbC3XHJLE4GpRQ== X-IronPort-AV: E=McAfee;i="6800,10657,11863"; a="90143910" X-IronPort-AV: E=Sophos;i="6.25,201,1779174000"; d="scan'208";a="90143910" Received: from fmviesa003.fm.intel.com ([10.60.135.143]) by orvoesa106.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 02 Aug 2026 19:43:44 -0700 X-CSE-ConnectionGUID: BEG4ZP1DRymmaTKVaWpetA== X-CSE-MsgGUID: B7M1+kP7TIiUCgGwEr8Lcw== X-ExtLoop1: 1 Received: from xiaoyaol-hp-g830.ccr.corp.intel.com (HELO [10.124.240.248]) ([10.124.240.248]) by fmviesa003-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 02 Aug 2026 19:43:30 -0700 Message-ID: <25ab36cf-888a-4547-b3f7-5bd4e057c1d0@intel.com> Date: Mon, 3 Aug 2026 10:43:26 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v9 07/41] KVM: guest_memfd: Wire up core private/shared attribute interfaces To: Sean Christopherson Cc: Ackerley Tng , aik@amd.com, andrew.jones@linux.dev, binbin.wu@linux.intel.com, brauner@kernel.org, chao.p.peng@linux.intel.com, david@kernel.org, jmattson@google.com, jthoughton@google.com, michael.roth@amd.com, oupton@kernel.org, pankaj.gupta@amd.com, qperret@google.com, rick.p.edgecombe@intel.com, rientjes@google.com, shivankg@amd.com, steven.price@arm.com, tabba@google.com, willy@infradead.org, wyihan@google.com, yan.y.zhao@intel.com, forkloop@google.com, pratyush@kernel.org, suzuki.poulose@arm.com, aneesh.kumar@kernel.org, liam@infradead.org, Paolo Bonzini , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Steven Rostedt , Masami Hiramatsu , Mathieu Desnoyers , Jonathan Corbet , Shuah Khan , Shuah Khan , Vishal Annapurve , Andrew Morton , Chris Li , Kairui Song , Kemeng Shi , Nhat Pham , Barry Song , Axel Rasmussen , Yuanchu Xie , Wei Xu , Youngjun Park , Qi Zheng , Shakeel Butt , Kiryl Shutsemau , Baoquan He , Jason Gunthorpe , John Hubbard , Peter Xu , Vlastimil Babka , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-mm@kvack.org, linux-coco@lists.linux.dev References: <20260728-gmem-inplace-conversion-v9-0-35f9aec2aed2@google.com> <20260728-gmem-inplace-conversion-v9-7-35f9aec2aed2@google.com> <60d19013-d6d7-4eec-827a-2622e22cec98@intel.com> Content-Language: en-US From: Xiaoyao Li In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 8/1/2026 12:26 AM, Sean Christopherson wrote: > On Fri, Jul 31, 2026, Xiaoyao Li wrote: >> On 7/31/2026 4:42 AM, Ackerley Tng wrote: >>> Xiaoyao Li writes: >>> >>>> On 7/29/2026 8:35 AM, Ackerley Tng via B4 Relay wrote: >>>>> diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c >>>>> index 33c9830190e2e..89cf922232920 100644 >>>>> --- a/virt/kvm/guest_memfd.c >>>>> +++ b/virt/kvm/guest_memfd.c >>>>> @@ -893,6 +893,27 @@ int kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memory_slot *slot, >>>>> EXPORT_SYMBOL_FOR_KVM_INTERNAL(kvm_gmem_get_pfn); >>>>> >>>>> #ifdef CONFIG_HAVE_KVM_ARCH_GMEM_POPULATE >>>>> +static bool kvm_range_is_private(struct file *file, pgoff_t index, >>>>> + size_t nr_pages, struct kvm *kvm, gfn_t gfn) >>>>> +{ >>>>> + struct inode *inode = file_inode(file); >>>>> + pgoff_t last = index + nr_pages - 1; >>>>> + struct maple_tree *mt; >>>>> + void *entry; >>>>> + >>>>> + if (!gmem_in_place_conversion) >>>>> + return kvm_range_has_vm_memory_attributes(kvm, gfn, gfn + nr_pages, >>>>> + KVM_MEMORY_ATTRIBUTE_PRIVATE, >>>>> + KVM_MEMORY_ATTRIBUTE_PRIVATE); >>>>> + >>>>> + mt = &GMEM_I(inode)->attributes; >>>>> + mt_for_each(mt, entry, index, last) { >>>>> + if (kvm_gmem_interpret_entry(inode, entry) != >>>>> + KVM_MEMORY_ATTRIBUTE_PRIVATE) >>>>> + return false; >>>>> + } >>>>> + return true; >>>>> +} >>>>> >>>>> static long __kvm_gmem_populate(struct kvm *kvm, struct kvm_memory_slot *slot, >>>>> struct file *file, gfn_t gfn, struct page *src_page, >>>>> @@ -913,9 +934,7 @@ static long __kvm_gmem_populate(struct kvm *kvm, struct kvm_memory_slot *slot, >>>>> >>>>> folio_unlock(folio); >>>>> >>>>> - if (!kvm_range_has_vm_memory_attributes(kvm, gfn, gfn + 1, >>>>> - KVM_MEMORY_ATTRIBUTE_PRIVATE, >>>>> - KVM_MEMORY_ATTRIBUTE_PRIVATE)) { >>>>> + if (!kvm_range_is_private(file, index, 1, kvm, gfn)) { >>>> >>>> It's checking if a single gfn is private. >>>> >>> >>> But with huge page support we'd need to check a range of gfns... I guess >>> there's the argument of not keeping complexity for the future, but in >>> this case it's undoing functionality for this series and probably adding >>> it back later. >> >> let's leave the work for huge page support in the future. > > It's not just for hugepage support, the core functionality is used in this series > by __kvm_gmem_set_attributes() in: > > KVM: guest_memfd: Return early if range already has requested attributes > >>>> We can just use kvm_mem_is_private()? And it seems can be a separate patch. >>>> >>> >>> Do you mean that this refactoring could be a separate patch? I could >>> refactor out kvm_range_is_private() in a separate patch, then put in the >>> mt_for_each() check in this patch together as part of all the rest of >>> the "wiring". >>> >>> I considered that but it seemed like the refactoring was too small to >>> separate out into another patch when the mt_for_each() part is going to >>> be in this patch anyway. >>> >>> Or, I could add an earlier patch to first replace the call to >>> kvm_range_has_vm_memory_attributes() with a call to check just 1 gfn, >>> then this wiring patch would be simpler. >>> >> >> This is what I meant. An earlier patch to just replace >> kvm_range_has_vm_memory_attributes() with kvm_mem_is_private(). Then we can >> drop this 'big' diff in this patch. >> >> If kvm_range_is_private() is useful/required by huge page support, then let >> the huge page series to introduce it. It has nothing to do with the in-place >> conversion series. > > If it weren't for the fact that the range-based search is used later in this > series, I would 100% agree with Xiaoyao. > But since the core logic is used and needed elsewhere, I don't see it a problem. Without introducing kvm_range_is_private() in this patch, the core logic of range-based search on gmem can still be introduced as kvm_gmem_range_has_attributes() directly in patch 10 or in a separate patch. > and because kvm_range_has_vm_memory_attributes() takes a range,> my vote is to provide the plumbing now, even though a small portion of it isn't > strictly necessary. So my initial feedback was "we can just use kvm_mem_is_private(kvm, gfn)". It makes code simpler. And as a bonus, the logic to choose between gmem-based attribute query and vm-based attribute query is hidden from the static call. The second bonus of dropping kvm_range_is_private() is that we can eliminate one more chunk in patch 20.