From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pj1-f73.google.com (mail-pj1-f73.google.com [209.85.216.73]) (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 40D4F2A1BA for ; Thu, 19 Jun 2025 01:50:40 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.216.73 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1750297841; cv=none; b=RCAuuOgCdXSzGb6EgtQ4ONKdbfTgn3h3V0zse6hbfTVngCVE/W1omUctmVUnxADB+PaRI5jPwiMY7FNkTSBKeMayVjcmGMSiRoVHvPb3ALsV5mc7itCxISyqPdNF5/bqM2t5zbnOLwHcldtkQjtnnUr+R3sl40dvJXySFuEDy84= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1750297841; c=relaxed/simple; bh=byNHkanhQbJdZ5XbDcaqI9g6pjljdL2hBTwL7tVfO/U=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=KzuB0bCGHqZ7uE6ewbYHi9ii/a+chI6ogDSDsL4uuLhg2vOZC+dbfQ/c6EtmbS3huGOrWDvZ/ivogbokdQ3gsYItvqkrC4aBb2PVFelJRuS35yTepvGZxMlYhewTqB3eGtlA1I4FpgLReeJCPB/PdY44yvuQfOymtwoeJopFMDo= 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=PNuljnV0; arc=none smtp.client-ip=209.85.216.73 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="PNuljnV0" Received: by mail-pj1-f73.google.com with SMTP id 98e67ed59e1d1-313ff01d2a6so189297a91.3 for ; Wed, 18 Jun 2025 18:50:40 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1750297839; x=1750902639; 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=oMyWfQw26TyUS5xbeLell4c85EVnEgCQej52N6NWW2o=; b=PNuljnV0p4vhvJPEt+ewN4i9wgi8l7gtAGSckE08SKnCVhVo891GYfiA7oW4/Kpjtc 2hKYnITtREgQkKPbpUg48KKe4D3n4s/XpnXpDW0v97E46A7NKLdevjZ1jqEnL3emu4Mz kR7CNMu9o2fjh7DAHrPQBSqy1y5bGlYhrZ6POfmt0l/EepqHusiwmBNO7nZyqDcpdh+0 mKIL7eKnXY7TjL9AJnDov8WAPT5610Ctk8uLWK1A5BA56jsNvOd0VxRBCg1yphk8RWWs CUPuKwCfueOWHbVIhjpct4KtKc8KRn2+79no66yjmGWsIfoAqMrDSTVTFN1hJrz22AA1 +S7w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1750297839; x=1750902639; 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=oMyWfQw26TyUS5xbeLell4c85EVnEgCQej52N6NWW2o=; b=J9XnjwJVIGk+qBfEKMFqs9FzRyiZFkDr/n8pRspPrQyAqd643tRQs1RJsgmjJXVVaW 1kM4CO8lZIIEpT09nTsqstZPkErYYdhPDlw80sJ9doA5EZT22D6p4QTTljzZBeFxGibF EghARat1Yu4fdk5Cc/V7TqoPx0oPz/GZ7lz/sfsGc4v1fpI+Ai9wGoKQJZg3e9HGKgaN 9OKcrwcDbeajngyX/fT4Rn7OpcyW7xKilrTRsiOpMsDunNhU0dafYZvli1/WhNtuBrHr fXEfzMLcOo1YuSVpdm5Z4QFkJ1q7S2H70hMvngJsZGpALvutW+aDsbh44Vg4eIey92ss n2wg== X-Forwarded-Encrypted: i=1; AJvYcCX8ReEeQbNWOTsUAfvAN+mDOJ18HLCvA1eJWtTBcdPBlK7yRmF9mTMKgDhnxtpsY3oJUG+WqKs=@lists.linux.dev X-Gm-Message-State: AOJu0Yw6mpc+6YVKszTshzqKuQUpnHlvYkCV+a/OZSZJhPp5hFOM7Nba 6D0bj14FUvp7Ecr9ggblRUnEwRS4YmFAxT2OiqdxAEr6DPZRzb5S7AVaLCPtFpBV5NgDqfTKtvp /bwRMSw== X-Google-Smtp-Source: AGHT+IFYrz5Id5uH6iXof80e1fCW/jK+FUGGZzqnfiU3o4Gv59B5LgfHnd+rsdx73+Z8UQC28CXkLiecz6U= X-Received: from pjyd13.prod.google.com ([2002:a17:90a:dfcd:b0:30a:31eb:ec8e]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a17:90a:d60b:b0:313:283e:e87c with SMTP id 98e67ed59e1d1-313f1c77731mr27133495a91.3.1750297839512; Wed, 18 Jun 2025 18:50:39 -0700 (PDT) Date: Wed, 18 Jun 2025 18:50:37 -0700 In-Reply-To: Precedence: bulk X-Mailing-List: kvmarm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20250611133330.1514028-1-tabba@google.com> <20250611133330.1514028-9-tabba@google.com> <68501fa5dce32_2376af294d1@iweiny-mobl.notmuch> <701c8716-dd69-4bf6-9d36-4f8847f96e18@redhat.com> <3fb0e82b-f4ef-402d-a33c-0b12e8aa990c@redhat.com> Message-ID: Subject: Re: [PATCH v12 08/18] KVM: guest_memfd: Allow host to map guest_memfd pages From: Sean Christopherson To: David Hildenbrand Cc: Fuad Tabba , Ira Weiny , kvm@vger.kernel.org, linux-arm-msm@vger.kernel.org, linux-mm@kvack.org, kvmarm@lists.linux.dev, pbonzini@redhat.com, chenhuacai@kernel.org, mpe@ellerman.id.au, anup@brainfault.org, paul.walmsley@sifive.com, palmer@dabbelt.com, aou@eecs.berkeley.edu, viro@zeniv.linux.org.uk, brauner@kernel.org, willy@infradead.org, akpm@linux-foundation.org, xiaoyao.li@intel.com, yilun.xu@intel.com, chao.p.peng@linux.intel.com, jarkko@kernel.org, amoorthy@google.com, dmatlack@google.com, isaku.yamahata@intel.com, mic@digikod.net, vbabka@suse.cz, vannapurve@google.com, ackerleytng@google.com, mail@maciej.szmigiero.name, michael.roth@amd.com, wei.w.wang@intel.com, liam.merwick@oracle.com, isaku.yamahata@gmail.com, kirill.shutemov@linux.intel.com, suzuki.poulose@arm.com, steven.price@arm.com, quic_eberman@quicinc.com, quic_mnalajal@quicinc.com, quic_tsoni@quicinc.com, quic_svaddagi@quicinc.com, quic_cvanscha@quicinc.com, quic_pderrin@quicinc.com, quic_pheragu@quicinc.com, catalin.marinas@arm.com, james.morse@arm.com, yuzenghui@huawei.com, oliver.upton@linux.dev, maz@kernel.org, will@kernel.org, qperret@google.com, keirf@google.com, roypat@amazon.co.uk, shuah@kernel.org, hch@infradead.org, jgg@nvidia.com, rientjes@google.com, jhubbard@nvidia.com, fvdl@google.com, hughd@google.com, jthoughton@google.com, peterx@redhat.com, pankaj.gupta@amd.com Content-Type: text/plain; charset="us-ascii" On Wed, Jun 18, 2025, Sean Christopherson wrote: > On Wed, Jun 18, 2025, David Hildenbrand wrote: > > > Ya, but that's more because guest_memfd only supports MAP_SHARED, versus KVM > > > really wanting to truly share the memory with the entire system. > > > Of course, that's also an argument to some extent against USER_MAPPABLE, because > > > that name assumes we'll never want to support MAP_PRIVATE. But letting userspace > > > MAP_PRIVATE guest_memfd would completely defeat the purpose of guest_memfd, so > > > unless I'm forgetting a wrinkle with MAP_PRIVATE vs. MAP_SHARED, that's an > > > assumption I'm a-ok making. > > > > So, first important question, are we okay with adding: > > > > "GUEST_MEMFD_FLAG_MMAP": we support the mmap() operation > > Probably stating the obvious, but yes, I am. Heh, my brain is a bit fried. I didn't realize you were asking about doing s/GUEST_MEMFD_FLAG_MMAPPABLE/GUEST_MEMFD_FLAG_MMAP until I read your other mail. Luckily, I 100% agree that GUEST_MEMFD_FLAG_MMAP is way better.