From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp-fw-52004.amazon.com (smtp-fw-52004.amazon.com [52.119.213.154]) (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 E60BE1EF36B for ; Thu, 26 Jun 2025 16:09:54 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=52.119.213.154 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1750954196; cv=none; b=SU7lDa1TWyQkqol0iC1ayFg+cWfhUSiWYcVwrXlMi2CWFrPbH19K0mgSbK0U4iGRXk5WJcE8MKHsD5amzxNvEChY1Vp+DKr64PDpXXhEptBa4cWKsugU40IP7UXaZ6YYsrGlUiFIrmwhTx0H+3qVXQ9YJWN1cpVNJgSxR+9mCNo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1750954196; c=relaxed/simple; bh=ytGi2CI81yYquxhb2ptqmJdqYDkJAscsvZjaIhReO/c=; h=Message-ID:Date:MIME-Version:Subject:To:CC:References:From: In-Reply-To:Content-Type; b=XeHOhe8pSZQzVhI/Mb6+TWPzdQgHISDhKpnrH5jkZGWMJPc/nRrEh3HM9lhDdgT0KADdKB5HcXnxYs3I0J02qNvWo8dEZWWDYtBepFFnebJ1TXMFupt2P8hEuuI62sssphswsezECnJ1Z/CxvGgv8sBFhCOoszF/6SzGU7Qz/q4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=amazon.com; spf=pass smtp.mailfrom=amazon.co.uk; dkim=pass (2048-bit key) header.d=amazon.com header.i=@amazon.com header.b=mx6hBOGa; arc=none smtp.client-ip=52.119.213.154 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=amazon.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=amazon.co.uk Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=amazon.com header.i=@amazon.com header.b="mx6hBOGa" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=amazon.com; i=@amazon.com; q=dns/txt; s=amazoncorp2; t=1750954195; x=1782490195; h=message-id:date:mime-version:reply-to:subject:to:cc: references:from:in-reply-to:content-transfer-encoding; bh=g3xFeXZI3QqRMs02H2fge/YdYUqqiszTKp89blpgsUg=; b=mx6hBOGaQ56EAUDX51Xr2de2hpVy+vBY0gqYSQep+mZhR0j58GR/J4aV ifvhnh5qlRMkmWLUmx/M8eRix+3XusjezgHQzsl4SqB2TGBbiMMyaEg/m jXMJk+R8cW2Zt+V9AQ4mkcFFqgf2/HGfcZDnvvAnsQcNFtEfPHIpboWgu ipOl09HpmhzQKyggHxCcDJno7S/nmxjuKST/XJd4GqKV3NSuZ22IUqsw/ G0DAwYwsYdZPzFlsAsI8QVzdMZjC8RtL7HyJDLULmCCG4+uZz1Wv2VjvM OLpLsOxk5sIpyM3sXmb0Qi9VU62Ro9qe98j6oNafEcJPgvkmajYHEFtSr w==; X-IronPort-AV: E=Sophos;i="6.16,268,1744070400"; d="scan'208";a="312994400" Received: from iad12-co-svc-p1-lb1-vlan2.amazon.com (HELO smtpout.prod.us-west-2.prod.farcaster.email.amazon.dev) ([10.43.8.2]) by smtp-border-fw-52004.iad7.amazon.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 26 Jun 2025 16:09:51 +0000 Received: from EX19MTAEUA001.ant.amazon.com [10.0.17.79:13317] by smtpin.naws.eu-west-1.prod.farcaster.email.amazon.dev [10.0.47.53:2525] with esmtp (Farcaster) id 5ba97137-2dfa-4eb8-9ed5-afeceeeb58e6; Thu, 26 Jun 2025 16:09:49 +0000 (UTC) X-Farcaster-Flow-ID: 5ba97137-2dfa-4eb8-9ed5-afeceeeb58e6 Received: from EX19D022EUC002.ant.amazon.com (10.252.51.137) by EX19MTAEUA001.ant.amazon.com (10.252.50.50) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA) id 15.2.1544.14; Thu, 26 Jun 2025 16:09:49 +0000 Received: from [192.168.30.146] (10.106.83.33) by EX19D022EUC002.ant.amazon.com (10.252.51.137) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA) id 15.2.1544.14; Thu, 26 Jun 2025 16:09:48 +0000 Message-ID: <7666ee96-6f09-4dc1-8cb2-002a2d2a29cf@amazon.com> Date: Thu, 26 Jun 2025 17:09:47 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Reply-To: Subject: Re: [PATCH 0/4] mm/userfaultfd: modulize memory types To: Peter Xu CC: , , Hugh Dickins , Oscar Salvador , Michal Hocko , David Hildenbrand , Muchun Song , Andrea Arcangeli , Ujwal Kundur , Suren Baghdasaryan , "Andrew Morton" , Vlastimil Babka , "Liam R . Howlett" , James Houghton , Mike Rapoport , Lorenzo Stoakes , Axel Rasmussen References: <20250620190342.1780170-1-peterx@redhat.com> <114133f5-0282-463d-9d65-3143aa658806@amazon.com> Content-Language: en-US From: Nikita Kalyazin Autocrypt: addr=kalyazin@amazon.com; keydata= xjMEY+ZIvRYJKwYBBAHaRw8BAQdA9FwYskD/5BFmiiTgktstviS9svHeszG2JfIkUqjxf+/N JU5pa2l0YSBLYWx5YXppbiA8a2FseWF6aW5AYW1hem9uLmNvbT7CjwQTFggANxYhBGhhGDEy BjLQwD9FsK+SyiCpmmTzBQJnrNfABQkFps9DAhsDBAsJCAcFFQgJCgsFFgIDAQAACgkQr5LK IKmaZPOpfgD/exazh4C2Z8fNEz54YLJ6tuFEgQrVQPX6nQ/PfQi2+dwBAMGTpZcj9Z9NvSe1 CmmKYnYjhzGxzjBs8itSUvWIcMsFzjgEY+ZIvRIKKwYBBAGXVQEFAQEHQCqd7/nb2tb36vZt ubg1iBLCSDctMlKHsQTp7wCnEc4RAwEIB8J+BBgWCAAmFiEEaGEYMTIGMtDAP0Wwr5LKIKma ZPMFAmes18AFCQWmz0MCGwwACgkQr5LKIKmaZPNTlQEA+q+rGFn7273rOAg+rxPty0M8lJbT i2kGo8RmPPLu650A/1kWgz1AnenQUYzTAFnZrKSsXAw5WoHaDLBz9kiO5pAK In-Reply-To: Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 7bit X-ClientProxiedBy: EX19D003EUB001.ant.amazon.com (10.252.51.97) To EX19D022EUC002.ant.amazon.com (10.252.51.137) On 25/06/2025 21:17, Peter Xu wrote: > On Wed, Jun 25, 2025 at 05:56:23PM +0100, Nikita Kalyazin wrote: >> >> >> On 20/06/2025 20:03, Peter Xu wrote: >>> [based on akpm/mm-new] >>> >>> This series is an alternative proposal of what Nikita proposed here on the >>> initial three patches: >>> >>> https://lore.kernel.org/r/20250404154352.23078-1-kalyazin@amazon.com >>> >>> This is not yet relevant to any guest-memfd support, but paving way for it. >> >> Hi Peter, > > Hi, Nikita, > >> >> Thanks for posting this. I confirmed that minor fault handling was working >> for guest_memfd based on this series and looked simple (a draft based on >> mmap support in guest_memfd v7 [1]): > > Thanks for the quick spin, glad to know it works. Some trivial things to > mention below.. Following up, I drafted UFFDIO_COPY support for guest_memfd to confirm it works as well: diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c index 8c44e4b9f5f8..b5458a22fff4 100644 --- a/virt/kvm/guest_memfd.c +++ b/virt/kvm/guest_memfd.c @@ -349,12 +349,19 @@ static bool kvm_gmem_offset_is_shared(struct file *file, pgoff_t index) static vm_fault_t kvm_gmem_fault(struct vm_fault *vmf) { + struct vm_area_struct *vma = vmf ? vmf->vma : NULL; struct inode *inode = file_inode(vmf->vma->vm_file); struct folio *folio; vm_fault_t ret = VM_FAULT_LOCKED; filemap_invalidate_lock_shared(inode->i_mapping); + folio = filemap_get_entry(inode->i_mapping, vmf->pgoff); + if (!folio && vma && userfaultfd_missing(vma)) { + filemap_invalidate_unlock_shared(inode->i_mapping); + return handle_userfault(vmf, VM_UFFD_MISSING); + } + folio = kvm_gmem_get_folio(inode, vmf->pgoff); if (IS_ERR(folio)) { int err = PTR_ERR(folio); @@ -438,10 +445,57 @@ static int kvm_gmem_uffd_get_folio(struct inode *inode, pgoff_t pgoff, return 0; } +static int kvm_gmem_mfill_atomic_pte(pmd_t *dst_pmd, + struct vm_area_struct *dst_vma, + unsigned long dst_addr, + unsigned long src_addr, + uffd_flags_t flags, + struct folio **foliop) +{ + struct inode *inode = file_inode(dst_vma->vm_file); + pgoff_t pgoff = linear_page_index(dst_vma, dst_addr); + struct folio *folio; + int ret; + + folio = kvm_gmem_get_folio(inode, pgoff); + if (IS_ERR(folio)) { + ret = PTR_ERR(folio); + goto out; + } + + folio_unlock(folio); + + if (uffd_flags_mode_is(flags, MFILL_ATOMIC_COPY)) { + void *vaddr = kmap_local_folio(folio, 0); + ret = copy_from_user(vaddr, (const void __user *)src_addr, PAGE_SIZE); + kunmap_local(vaddr); + if (unlikely(ret)) { + *foliop = folio; + ret = -ENOENT; + goto out; + } + } else { /* ZEROPAGE */ + clear_user_highpage(&folio->page, dst_addr); + } + + kvm_gmem_mark_prepared(folio); + + ret = mfill_atomic_install_pte(dst_pmd, dst_vma, dst_addr, + &folio->page, true, flags); + + if (ret) + folio_put(folio); +out: + return ret; +} + static const vm_uffd_ops kvm_gmem_uffd_ops = { - .uffd_features = VM_UFFD_MINOR, - .uffd_ioctls = BIT(_UFFDIO_CONTINUE), + .uffd_features = VM_UFFD_MISSING | VM_UFFD_MINOR, + .uffd_ioctls = BIT(_UFFDIO_COPY) | + BIT(_UFFDIO_ZEROPAGE) | + BIT(_UFFDIO_CONTINUE), .uffd_get_folio = kvm_gmem_uffd_get_folio, + .uffd_copy = kvm_gmem_mfill_atomic_pte, }; #endif > >> >> diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c >> index 5abb6d52a375..6ddc73419724 100644 >> --- a/virt/kvm/guest_memfd.c >> +++ b/virt/kvm/guest_memfd.c >> @@ -5,6 +5,9 @@ >> #include >> #include >> #include >> +#ifdef CONFIG_USERFAULTFD > > This ifdef not needed, userfaultfd_k.h has taken care of all cases. Good to know, thanks. >> +#include >> +#endif >> >> #include "kvm_mm.h" >> >> @@ -396,6 +399,14 @@ static vm_fault_t kvm_gmem_fault(struct vm_fault *vmf) >> kvm_gmem_mark_prepared(folio); >> } >> >> +#ifdef CONFIG_USERFAULTFD > > Same here. userfaultfd_minor() is always defined. Thank you. > I'll wait for a few more days for reviewers, and likely send v2 before next > week. > > Thanks, > > -- > Peter Xu >