From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-170.mta0.migadu.com (out-170.mta0.migadu.com [91.218.175.170]) (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 D9E293009F6 for ; Fri, 26 Jun 2026 14:45:58 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.170 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782485166; cv=none; b=kV1uxyd9R1DjSpKA/2Roswc3wDzXuWTtspu+HpoH4kUJL3rtZiVBkM9eqUPMsvXHGnbSb9x8teOTTAFiShy+Upe4SMko19n0hhIniJldrEChsVNFsWPSjVrLeeHYGju9KAC8I6lJHbXN+nDA2u0664ugMm52lL7xYKI0r2YhzsM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782485166; c=relaxed/simple; bh=BgssH8vCKDppnzbwBoJeH2HdO6TiCS4MwxNCxIwOGxg=; h=Mime-Version:Content-Type:Date:Message-Id:Cc:Subject:From:To: References:In-Reply-To; b=dkJajmv3Ru1jQ31iWmKyMFkGvzJ0QI+nvTH9MrjilcLuxE4WVRemjBt/tNOblPcqGtJOr8GFFjBcZ9qwaTd0u2hGok+nZ0vB36t+ZwNVhlMQtY+piiD2x2tZHBKOeb8Qad7ROauiTtG5B28J8Ri/nOctk1FYG/sxYo3GX9rsn7c= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=xBmLvvo9; arc=none smtp.client-ip=91.218.175.170 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="xBmLvvo9" Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1782485154; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=hLoe9hgpuLGAv9HcjQXiuki+Z1Eo9W05Z+080Efe+Rc=; b=xBmLvvo9VeLWl6aCPOHJfACC84T1J3BTjH51kQr8iuIJvUHkpL0TY/1jmfKt3pAIas6Dh6 hMKA2it5f7Povtcv7HNEPaX/tbq52whxslXQwIYDMnFdkUFHHwDlaTZMjI6N1SUuxeL0dB Mk0ZoJAcKfnjrWev0iaDEvycix+RYjk= Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=UTF-8 Date: Fri, 26 Jun 2026 14:45:45 +0000 Message-Id: Cc: "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" , "linux-pm@vger.kernel.org" , "pbonzini@redhat.com" , "corbet@lwn.net" , "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" , "david@kernel.org" , "lorenzo.stoakes@oracle.com" , "vbabka@kernel.org" , "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" , "skhan@linuxfoundation.org" , "riel@surriel.com" , "ryan.roberts@arm.com" , "jgross@suse.com" , "yu-cheng.yu@intel.com" , "kas@kernel.org" , "coxu@redhat.com" , "ackerleytng@google.com" , "yosry@kernel.org" , "ajones@ventanamicro.com" , "maobibo@loongson.cn" , "tabba@google.com" , "prsampat@amd.com" , "wu.fei9@sanechips.com.cn" , "mlevitsk@redhat.com" , "jmattson@google.com" , "jthoughton@google.com" , "agordeev@linux.ibm.com" , "alex@ghiti.fr" , "borntraeger@linux.ibm.com" , "chenhuacai@kernel.org" , "baolu.lu@linux.intel.com" , "dev.jain@arm.com" , "palmer@dabbelt.com" , "pjw@kernel.org" , "shijie@os.amperecomputing.com" , "thuth@redhat.com" , "yang@os.amperecomputing.com" , "Liam.Howlett@oracle.com" , "zhengqi.arch@bytedance.com" , "lenb@kernel.org" , "pavel@kernel.org" , "yangyicong@hisilicon.com" , "vannapurve@google.com" , "jackmanb@google.com" , "patrick.roy@linux.dev" , "Itazuri, Takahiro" Subject: Re: [PATCH v12 09/16] KVM: arm64: define kvm_arch_gmem_supports_no_direct_map() X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: "Brendan Jackman" To: "Marc Zyngier" , "Kalyazin, Nikita" References: <20260410151746.61150-1-kalyazin@amazon.com> <20260410151746.61150-10-kalyazin@amazon.com> <86fr4o1ceu.wl-maz@kernel.org> In-Reply-To: <86fr4o1ceu.wl-maz@kernel.org> X-Migadu-Flow: FLOW_OUT On Tue Apr 21, 2026 at 4:55 PM UTC, Marc Zyngier wrote: > On Fri, 10 Apr 2026 16:19:24 +0100, > "Kalyazin, Nikita" wrote: >>=20 >> From: Patrick Roy >>=20 >> 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. >>=20 >> 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. > > Where is this 4kB requirement enforced? Or is it that you means > "PAGE_SIZE"? Yeah I believe this means PAGE_SIZE and that it's effectively enforced by checking can_set_direct_map() in kvm_arch_gmem_supports_no_direct_map().