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X-CSE-ConnectionGUID: IhdtliZnSimC56BFLDZy+A== X-CSE-MsgGUID: EaMNa3iVR3e9eRy+nRpZVA== X-IronPort-AV: E=McAfee;i="6800,10657,11490"; a="65104679" X-IronPort-AV: E=Sophos;i="6.16,303,1744095600"; d="scan'208";a="65104679" Received: from orviesa005.jf.intel.com ([10.64.159.145]) by fmvoesa105.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 11 Jul 2025 02:42:42 -0700 X-CSE-ConnectionGUID: Ry1VIS8iTJqgroNk8yFFkw== X-CSE-MsgGUID: QqzhhYC7SZuEOXM1tMmJxA== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.16,303,1744095600"; d="scan'208";a="162019431" Received: from yilunxu-optiplex-7050.sh.intel.com (HELO localhost) ([10.239.159.165]) by orviesa005.jf.intel.com with ESMTP; 11 Jul 2025 02:42:22 -0700 Date: Fri, 11 Jul 2025 17:33:59 +0800 From: Xu Yilun To: Jason Gunthorpe Cc: Vishal Annapurve , Yan Zhao , Alexey Kardashevskiy , Fuad Tabba , Ackerley Tng , kvm@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, x86@kernel.org, linux-fsdevel@vger.kernel.org, ajones@ventanamicro.com, akpm@linux-foundation.org, amoorthy@google.com, anthony.yznaga@oracle.com, anup@brainfault.org, aou@eecs.berkeley.edu, bfoster@redhat.com, binbin.wu@linux.intel.com, brauner@kernel.org, catalin.marinas@arm.com, chao.p.peng@intel.com, chenhuacai@kernel.org, dave.hansen@intel.com, david@redhat.com, dmatlack@google.com, dwmw@amazon.co.uk, erdemaktas@google.com, fan.du@intel.com, fvdl@google.com, graf@amazon.com, haibo1.xu@intel.com, hch@infradead.org, hughd@google.com, ira.weiny@intel.com, isaku.yamahata@intel.com, jack@suse.cz, james.morse@arm.com, jarkko@kernel.org, jgowans@amazon.com, jhubbard@nvidia.com, jroedel@suse.de, jthoughton@google.com, jun.miao@intel.com, kai.huang@intel.com, keirf@google.com, kent.overstreet@linux.dev, kirill.shutemov@intel.com, liam.merwick@oracle.com, maciej.wieczor-retman@intel.com, mail@maciej.szmigiero.name, maz@kernel.org, mic@digikod.net, michael.roth@amd.com, mpe@ellerman.id.au, muchun.song@linux.dev, nikunj@amd.com, nsaenz@amazon.es, oliver.upton@linux.dev, palmer@dabbelt.com, pankaj.gupta@amd.com, paul.walmsley@sifive.com, pbonzini@redhat.com, pdurrant@amazon.co.uk, peterx@redhat.com, pgonda@google.com, pvorel@suse.cz, qperret@google.com, quic_cvanscha@quicinc.com, quic_eberman@quicinc.com, quic_mnalajal@quicinc.com, quic_pderrin@quicinc.com, quic_pheragu@quicinc.com, quic_svaddagi@quicinc.com, quic_tsoni@quicinc.com, richard.weiyang@gmail.com, rick.p.edgecombe@intel.com, rientjes@google.com, roypat@amazon.co.uk, rppt@kernel.org, seanjc@google.com, shuah@kernel.org, steven.price@arm.com, steven.sistare@oracle.com, suzuki.poulose@arm.com, thomas.lendacky@amd.com, usama.arif@bytedance.com, vbabka@suse.cz, viro@zeniv.linux.org.uk, vkuznets@redhat.com, wei.w.wang@intel.com, will@kernel.org, willy@infradead.org, xiaoyao.li@intel.com, yilun.xu@intel.com, yuzenghui@huawei.com, zhiquan1.li@intel.com Subject: Re: [RFC PATCH v2 04/51] KVM: guest_memfd: Introduce KVM_GMEM_CONVERT_SHARED/PRIVATE ioctls Message-ID: References: <9502503f-e0c2-489e-99b0-94146f9b6f85@amd.com> <20250624130811.GB72557@ziepe.ca> <20250702141321.GC904431@ziepe.ca> <20250710175449.GA1870174@ziepe.ca> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Queue-Id: 109EF20011 X-Stat-Signature: adf334zp5t15wdizctdn9ct14rd6tsog X-Rspam-User: X-Rspamd-Server: rspam10 X-HE-Tag: 1752226963-195411 X-HE-Meta: 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 QGUtDQm1 2FDd6wbEas7UttPa3eX1lOdI7YH7W2B0cYg2hmirF/gbdN1rCmJm9AKC1xWlaCvHxEu6MM9wAPlf1zT3cOazwN4KB018ZpMwGnkO0/3npoM1e6PUmrGSJ3MJteSM8BsBxqjYmrsRR0hz+uzjKAf4uok3M7ZynzVeE6YxMSRpKwV7vjS0Xps7Jn56OdcP1xhY608eavI1voT6UwXD/Dsv+GHFS5ABGuT+IhUGRrp9dWYoL6rFyg5ewjboUVzdzCav1ZIhBa/iI7R8uwegZKaeqrDeU62ZO0T2JE1cIbRd4Ji/SM3GEz+jQltcurYrVG2OEIMWJxOjiGI4jW/jHOEERPIrvgQ== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: > > > > > > Only *guest permitted* conversion should change the page. I.e only when > > > VMM is dealing with the KVM_HC_MAP_GPA_RANGE hypercall. Not sure if we > > > could just let QEMU ensure this or KVM/guestmemfd should ensure this. > > > > I think it should not be part of the kernel, no need. From a kernel > > perspective userspace has requested a shared/private conversion and if > > it wasn't agreed with the VM then it will explode. > > I'm OK with it now. It's simple if we don't try to recover from the > explosion. Although I see the after explosion processing in kernel is > complex and not sure how it will advance. I see the discussion in another thread about similar issue. That TDX Module BUG causes S-EPT unmap impossible and just KVM_BUG_ON(). But this conversion issue is a little different, usually it's not decent to panic because of userspace request. So may need further error handling, or a KVM/gmemfd kAPI to disallow/allow conversion and prevent more complex error. Thanks, Yilun > > Thanks, > Yilun > > > > > Jason >