From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 E97E8299922; Thu, 5 Mar 2026 19:09:07 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772737748; cv=none; b=IXOf3GT1TOlJihCsbgO8CqPlVAI6F4UNzCx3RHAlkBfazmlONtt0ec7zwlKDjLLybQsAJq+gk8lIBocSzPilFUDMWCxNcGyQNIHPA0uh7DBLz7rppyr0b3fqhFqDDhg8+zelHvj3z/dXuxe8uah5j44ndgHSAJtF5c1kpI9SUBs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772737748; c=relaxed/simple; bh=xnFSI//R+BzfODKG1aZ4cttDCVjiU+SClWrr7aM8b7Q=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=Hu/xZbKPXjaWNetYhDn7zqH5TCivO/NiDbRhxcCIAWnFNfbVSYU3Vby15gN0a1sEbVCbzYcyUN8DxY1HLa5heTV/jsCcerFf0IAKJ04UExw1tFIeNKz2b/Ek6FORjV/X7j8AdnEQub4qwk0ooS+poUwRFHxpVFOWfaZBfucm1T0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=fB5u5dyt; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="fB5u5dyt" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5DA3AC2BC9E; Thu, 5 Mar 2026 19:08:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1772737747; bh=xnFSI//R+BzfODKG1aZ4cttDCVjiU+SClWrr7aM8b7Q=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=fB5u5dytoZH+98uvrjhJSL5NnZlmf5fZGsPzyhYrfyvhJwXiRppGmJoTmejP5T5Fz M5bhvSqL7jNYBfd44Mmd8LdzPSbjjn000TOHUGTfXPSvvD1K6sHJQheZgf9+2anLeE KQj+KiDnMsmWGniNFlZcWw4yp+uiBDungqoO4t1eBUfLMmYHda4BK70uoqKyb0GZlu 0fE/39irRV0Yhqn6CgM40sNBVNXmpzvmeSC/QK46uQ/PUoNFYSTAP1qunpWSnetVz8 0APFZjBhTQzg0DrLw6zK1CTVW6w3sXi7p0RCCw/fdSIa+0Ekybcr8xgpjtAE0ge5y3 l5gh4QLZuMQrQ== Message-ID: Date: Thu, 5 Mar 2026 20:08:35 +0100 Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v10 08/15] KVM: arm64: define kvm_arch_gmem_supports_no_direct_map() To: "Kalyazin, Nikita" , "kvm@vger.kernel.org" , "linux-doc@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" , "kvmarm@lists.linux.dev" , "linux-fsdevel@vger.kernel.org" , "linux-mm@kvack.org" , "bpf@vger.kernel.org" , "linux-kselftest@vger.kernel.org" , "kernel@xen0n.name" , "linux-riscv@lists.infradead.org" , "linux-s390@vger.kernel.org" , "loongarch@lists.linux.dev" Cc: "pbonzini@redhat.com" , "corbet@lwn.net" , "maz@kernel.org" , "oupton@kernel.org" , "joey.gouly@arm.com" , "suzuki.poulose@arm.com" , "yuzenghui@huawei.com" , "catalin.marinas@arm.com" , "will@kernel.org" , "seanjc@google.com" , "tglx@kernel.org" , "mingo@redhat.com" , "bp@alien8.de" , "dave.hansen@linux.intel.com" , "x86@kernel.org" , "hpa@zytor.com" , "luto@kernel.org" , "peterz@infradead.org" , "willy@infradead.org" , "akpm@linux-foundation.org" , "lorenzo.stoakes@oracle.com" , "vbabka@suse.cz" , "rppt@kernel.org" , "surenb@google.com" , "mhocko@suse.com" , "ast@kernel.org" , "daniel@iogearbox.net" , "andrii@kernel.org" , "martin.lau@linux.dev" , "eddyz87@gmail.com" , "song@kernel.org" , "yonghong.song@linux.dev" , "john.fastabend@gmail.com" , "kpsingh@kernel.org" , "sdf@fomichev.me" , "haoluo@google.com" , "jolsa@kernel.org" , "jgg@ziepe.ca" , "jhubbard@nvidia.com" , "peterx@redhat.com" , "jannh@google.com" , "pfalcato@suse.de" , "shuah@kernel.org" , "riel@surriel.com" , "ryan.roberts@arm.com" , "jgross@suse.com" , "yu-cheng.yu@intel.com" , "kas@kernel.org" , "coxu@redhat.com" , "kevin.brodsky@arm.com" , "ackerleytng@google.com" , "maobibo@loongson.cn" , "prsampat@amd.com" , "mlevitsk@redhat.com" , "jmattson@google.com" , "jthoughton@google.com" , "agordeev@linux.ibm.com" , "alex@ghiti.fr" , "aou@eecs.berkeley.edu" , "borntraeger@linux.ibm.com" , "chenhuacai@kernel.org" , "dev.jain@arm.com" , "gor@linux.ibm.com" , "hca@linux.ibm.com" , "palmer@dabbelt.com" , "pjw@kernel.org" , "shijie@os.amperecomputing.com" , "svens@linux.ibm.com" , "thuth@redhat.com" , "wyihan@google.com" , "yang@os.amperecomputing.com" , "Jonathan.Cameron@huawei.com" , "Liam.Howlett@oracle.com" , "urezki@gmail.com" , "zhengqi.arch@bytedance.com" , "gerald.schaefer@linux.ibm.com" , "jiayuan.chen@shopee.com" , "lenb@kernel.org" , "osalvador@suse.de" , "pavel@kernel.org" , "rafael@kernel.org" , "vannapurve@google.com" , "jackmanb@google.com" , "aneesh.kumar@kernel.org" , "patrick.roy@linux.dev" , "Thomson, Jack" , "Itazuri, Takahiro" , "Manwaring, Derek" , "Cali, Marco" References: <20260126164445.11867-1-kalyazin@amazon.com> <20260126164445.11867-9-kalyazin@amazon.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 1/26/26 17:50, Kalyazin, Nikita wrote: > From: Patrick Roy > > Support for GUEST_MEMFD_FLAG_NO_DIRECT_MAP on arm64 depends on 1) direct > map manipulations at 4k granularity being possible, and 2) FEAT_S2FWB. > > 1) is met whenever the direct map is set up at 4k granularity (e.g. not > with huge/gigantic pages) at boottime, as due to ARM's > break-before-make semantics, breaking huge mappings into 4k mappings in > the direct map is not possible (BBM would require temporary invalidation > of the entire huge mapping, even if only a 4k subrange should be zapped, > which will probably crash the kernel). However, the current default for > rodata_full is true, which forces a 4k direct map. > > 2) is required to allow KVM to elide cache coherency operations when > installing stage 2 page tables, which require the direct map to be > entry for the newly mapped memory to be present (which it will not be, > as guest_memfd would have removed direct map entries in > kvm_gmem_get_pfn()). > > Cc: Will Deacon > Signed-off-by: Patrick Roy > Signed-off-by: Nikita Kalyazin > --- Reviewed-by: David Hildenbrand (Arm) -- Cheers, David