From nobody Tue Feb 10 04:12:41 2026 Received: from fra-out-014.esa.eu-central-1.outbound.mail-perimeter.amazon.com (fra-out-014.esa.eu-central-1.outbound.mail-perimeter.amazon.com [18.199.210.3]) (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 F1CBC264A9D; Wed, 14 Jan 2026 13:46:22 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=18.199.210.3 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768398391; cv=none; b=g6WnTftwpoU+B89xHoTLKmK/OKG4h1rfWxFOyFplkIOrflSPrKkTT2gVjUmFEUbt6ZE63ezDkeYZ5LpvbNhdoMTuGQLN+YGmFRhAOypuPrSJv3BhQZkQylco1bkA7O9S2VS0Odrp5gA5sZCAq9SMdSZZ+jjAmg7JiS+nWfhKx0I= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768398391; c=relaxed/simple; bh=tAdD+RAeqMq3JW4udflyWKRzYVu8+JPA6rbc8uczf6Q=; h=From:To:CC:Subject:Date:Message-ID:References:In-Reply-To: Content-Type:MIME-Version; b=lnpz0SQr0UvhzOk9DjMn4pIiYX8Z9saP+3xFLP4i0Ozv1yWcRqtqCSC6zNlWF5W5pUHKohVLEKE96z7x3lVpOVoeB0iG5QrSBehB5OQTxKYJqjJ+c5CWpT0AMhl6itG6L/N9pmvPukJhpeXiQ532Kj5XU7IAAOirynAecjMHgCY= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=amazon.co.uk; spf=pass smtp.mailfrom=amazon.co.uk; dkim=pass (2048-bit key) header.d=amazon.co.uk header.i=@amazon.co.uk header.b=Q3l8nJYO; arc=none smtp.client-ip=18.199.210.3 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=amazon.co.uk Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=amazon.co.uk Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=amazon.co.uk header.i=@amazon.co.uk header.b="Q3l8nJYO" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=amazon.co.uk; i=@amazon.co.uk; q=dns/txt; s=amazoncorp2; t=1768398384; x=1799934384; h=from:to:cc:subject:date:message-id:references: in-reply-to:content-transfer-encoding:mime-version; bh=Z+0YCRdTDnWSs97jpjMZOSlIedfR2zbQnGU/yn7jp+s=; b=Q3l8nJYOAyhFDrvWDn2Gx86mJMtS044ywk/AvdJH/UmZMj4gM33ML05m 5BN2hBx8PvN08L1Ez4SjtpAitce1fKChMs/h3hV+M/qwzZHfwn5PmDxk2 0nLHkSmj5xqGYRXR0T/januEkpPLfxR3n8bkKelYsAqpWoQAbNnx4KqKw +MNcwf8Q3lV+Ib9J7ULRrX8SQ/YR3NCXNjQmKyzjjhfBTe6B1mmzInyS3 X2/oTd29BfugVD5bsKYjSqcCTTDNfrSriuqfFhO22E/+SItDNR7amw9G9 5FFM9ySNi0RNld82eURuE538xzLkb3sYq3dTjp9ScgzcKEzlB8CVzSiYU Q==; X-CSE-ConnectionGUID: XXxyITF9Rw6G0U/xRLGdXw== X-CSE-MsgGUID: /aFraT7BTL+DRqLIi0LPcw== X-IronPort-AV: E=Sophos;i="6.21,225,1763424000"; d="scan'208";a="7804606" Received: from ip-10-6-6-97.eu-central-1.compute.internal (HELO smtpout.naws.eu-central-1.prod.farcaster.email.amazon.dev) ([10.6.6.97]) by internal-fra-out-014.esa.eu-central-1.outbound.mail-perimeter.amazon.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 14 Jan 2026 13:46:22 +0000 Received: from EX19MTAEUC002.ant.amazon.com [54.240.197.228:20934] by smtpin.naws.eu-central-1.prod.farcaster.email.amazon.dev [10.0.6.3:2525] with esmtp (Farcaster) id 62714440-81e8-4fb7-aff1-a3fc1349bab0; Wed, 14 Jan 2026 13:46:22 +0000 (UTC) X-Farcaster-Flow-ID: 62714440-81e8-4fb7-aff1-a3fc1349bab0 Received: from EX19D005EUB001.ant.amazon.com (10.252.51.12) by EX19MTAEUC002.ant.amazon.com (10.252.51.181) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA) id 15.2.2562.35; Wed, 14 Jan 2026 13:46:21 +0000 Received: from EX19D005EUB003.ant.amazon.com (10.252.51.31) by EX19D005EUB001.ant.amazon.com (10.252.51.12) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA) id 15.2.2562.35; Wed, 14 Jan 2026 13:46:21 +0000 Received: from EX19D005EUB003.ant.amazon.com ([fe80::b825:becb:4b38:da0c]) by EX19D005EUB003.ant.amazon.com ([fe80::b825:becb:4b38:da0c%3]) with mapi id 15.02.2562.035; Wed, 14 Jan 2026 13:46:21 +0000 From: "Kalyazin, Nikita" To: "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@linutronix.de" , "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" , "Liam.Howlett@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" , "Jonathan.Cameron@huawei.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" , "vannapurve@google.com" , "jackmanb@google.com" , "aneesh.kumar@kernel.org" , "patrick.roy@linux.dev" , "Thomson, Jack" , "Itazuri, Takahiro" , "Manwaring, Derek" , "Cali, Marco" , "Kalyazin, Nikita" Subject: [PATCH v9 06/13] KVM: arm64: define kvm_arch_gmem_supports_no_direct_map() Thread-Topic: [PATCH v9 06/13] KVM: arm64: define kvm_arch_gmem_supports_no_direct_map() Thread-Index: AQHchVwqXAUms8uaREatvOc5mFxAXg== Date: Wed, 14 Jan 2026 13:46:21 +0000 Message-ID: <20260114134510.1835-7-kalyazin@amazon.com> References: <20260114134510.1835-1-kalyazin@amazon.com> In-Reply-To: <20260114134510.1835-1-kalyazin@amazon.com> Accept-Language: en-GB, en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: Content-Transfer-Encoding: quoted-printable Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" 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 --- arch/arm64/include/asm/kvm_host.h | 13 +++++++++++++ 1 file changed, 13 insertions(+) diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm= _host.h index ac7f970c7883..d431ca7d4fc9 100644 --- a/arch/arm64/include/asm/kvm_host.h +++ b/arch/arm64/include/asm/kvm_host.h @@ -19,6 +19,7 @@ #include #include #include +#include #include #include #include @@ -1654,5 +1655,17 @@ static __always_inline enum fgt_group_id __fgt_reg_t= o_group_id(enum vcpu_sysreg \ p; \ }) +#ifdef CONFIG_KVM_GUEST_MEMFD +static inline bool kvm_arch_gmem_supports_no_direct_map(void) +{ + /* + * Without FWB, direct map access is needed in kvm_pgtable_stage2_map(), + * as it calls dcache_clean_inval_poc(). + */ + return can_set_direct_map() && cpus_have_final_cap(ARM64_HAS_STAGE2_FWB); +} +#define kvm_arch_gmem_supports_no_direct_map kvm_arch_gmem_supports_no_dir= ect_map +#endif /* CONFIG_KVM_GUEST_MEMFD */ + =20 #endif /* __ARM64_KVM_HOST_H__ */ --=20 2.50.1