From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mgamail.intel.com (mgamail.intel.com [198.175.65.13]) (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 9CF8246AED1; Wed, 1 Jul 2026 11:18:51 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.175.65.13 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782904734; cv=none; b=elMn/x79wMJ5UyMSj+4x67THzv9j5Q8KS9iry7M7CWGhRlkFpvILiJf0jsVfJpJYrSVm53OKN3VyHkzUb/R450jS1qsROYKu6HX+sjeBOyuV86rumqFd4o13IV3uGSCPU7VtwWGqiyxcAGsm9m1Xhc94idaPXJ+cFeUOSNGAXh0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782904734; c=relaxed/simple; bh=KamIF/GbQilflin+sZ24rcVjwHbCunBsl6fGoIU62PA=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=tPsf36bdNNdRJmlagAJ4grMkf38KL0r9m9rFwNILZOOcOeyKjFVIqynuvZ3X0OCbC7IUm5w/+kkOukyDwG3l2SVDGhfgdm1KhbtXlZF2kjPK4vgdiT3pXVuL1ghPgpSZEvtmF7X5emBJHOgFkRsiUsfzpvixy1hxyE2zFHoPXuY= 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=dndkJ/bV; arc=none smtp.client-ip=198.175.65.13 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="dndkJ/bV" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1782904732; x=1814440732; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=KamIF/GbQilflin+sZ24rcVjwHbCunBsl6fGoIU62PA=; b=dndkJ/bVaRCVaQzTmC4eOUHdIbDPWWipZbV2aOIFYUgA3LgEp7wbC2Fe OTGygtlSlA3cku7q9IDPHGtQHg1LhhPkV+mMTsu0vHiqdjoGIOEeinfOU F7J0MdA+MbLru1MYrhn3i6lGH74iehhi0xHrOqIiTDF2tMT5KxniTXYeW SH3fMovFU6YfEHDi1hs6TSVIr4qhVIHpTFQAlXnhBC4b8uIooM4d/2RTS pK3lYsmvyMHbkpeD8y6znLxMDdoJaR3xNI89uo879LcuEZStJbns8ne45 TIZpG43M44JFaLjHjjiPMXDyo9ETzkM+SxBrDUD4WUgzsiEqQmVStfr9P g==; X-CSE-ConnectionGUID: dmsaC05wSCGtx9ZNbqtT8A== X-CSE-MsgGUID: OYdVayxLQl2wHyN9HqHIEg== X-IronPort-AV: E=McAfee;i="6800,10657,11833"; a="94789715" X-IronPort-AV: E=Sophos;i="6.25,141,1779174000"; d="scan'208";a="94789715" Received: from orviesa004.jf.intel.com ([10.64.159.144]) by orvoesa105.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 01 Jul 2026 04:18:50 -0700 X-CSE-ConnectionGUID: aLlyHiwUTXyhs4lgY+f9QQ== X-CSE-MsgGUID: bSTU4KQCQOiPSgzMr577Lw== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.25,141,1779174000"; d="scan'208";a="256461895" Received: from unknown (HELO [10.239.158.49]) ([10.239.158.49]) by orviesa004-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 01 Jul 2026 04:18:31 -0700 Message-ID: Date: Wed, 1 Jul 2026 19:18:27 +0800 Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v8 25/46] KVM: guest_memfd: Enable INIT_SHARED on guest_memfd for x86 Coco VMs To: ackerleytng@google.com, 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 , Sean Christopherson , 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 , Vlastimil Babka Cc: 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: <20260618-gmem-inplace-conversion-v8-0-9d2959357853@google.com> <20260618-gmem-inplace-conversion-v8-25-9d2959357853@google.com> Content-Language: en-US From: Xiaoyao Li In-Reply-To: <20260618-gmem-inplace-conversion-v8-25-9d2959357853@google.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 6/19/2026 8:32 AM, Ackerley Tng via B4 Relay wrote: > From: Sean Christopherson > > Now that guest_memfd supports tracking private vs. shared within gmem > itself, allow userspace to specify INIT_SHARED on a guest_memfd instance > for x86 Confidential Computing (CoCo) VMs, so long as in-place conversion > is enabled, i.e. when it's actually possible for a guest_memfd instance to > contain shared memory. > > Signed-off-by: Sean Christopherson > Reviewed-by: Fuad Tabba > Signed-off-by: Ackerley Tng Reviewed-by: Xiaoyao Li > --- > arch/x86/kvm/x86.c | 13 +++++++------ > 1 file changed, 7 insertions(+), 6 deletions(-) > > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index 2fde594e86d72..57a543dadb851 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -14116,14 +14116,15 @@ bool kvm_arch_no_poll(struct kvm_vcpu *vcpu) > } > > #ifdef CONFIG_KVM_GUEST_MEMFD > -/* > - * KVM doesn't yet support initializing guest_memfd memory as shared for VMs > - * with private memory (the private vs. shared tracking needs to be moved into > - * guest_memfd). > - */ > bool kvm_arch_supports_gmem_init_shared(struct kvm *kvm) > { > - return !kvm_arch_has_private_mem(kvm); > + /* > + * INIT_SHARED is supported if in-place conversion is enabled, or if > + * the VM doesn't support private memory. If the VM has private memory > + * and in-place conversion is disabled, then guest_memfd can _only_ be > + * used for private memory. > + */ > + return gmem_in_place_conversion || !kvm_arch_has_private_mem(kvm); > } > > #ifdef CONFIG_HAVE_KVM_ARCH_GMEM_PREPARE >