From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-181.mta1.migadu.com (out-181.mta1.migadu.com [95.215.58.181]) (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 812B647F2E1 for ; Wed, 8 Jul 2026 18:25:30 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.181 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783535132; cv=none; b=PRbGoOjA8TY+SgWAiFcs37NYq3O36QsGiBpyBdFPL7N+Xa2dIVZ1FdBgDulyQ/OTEzTMVxfrTU5HMyNFyL3WGYqxPLVYAAHjAhRV/3FAwQRbgQJCVC36XJnnwwCS1uKXCvMDhQxhXw85bPwqClBtHIkOCoJDZ6x+GsbuGbEjlrE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783535132; c=relaxed/simple; bh=oj/mZ7j7m7tAdRaEW6908drAVJE0bDqnIe+Iej2Rz6k=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=pn6eekYuYRqe4GfdJhhgwITItRFQdWb1AJSQ4D8yn+gO9s+LiXBojucqxLkFvvYtbN3/h7OsAvBUaKfopo4cBR9WJXURSH8sRYmISdGGg2IcdvcTn44QxKHx4Cvpro93StCcS+ad8EIm0zOvCCrx9B6j7D/wHlMaF/Ki+0b5EmY= 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=ufJntv3P; arc=none smtp.client-ip=95.215.58.181 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="ufJntv3P" X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1783535128; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=PeN62wsw32unf+IwkMPfWPj+tyz624imy5YFSL35Xm4=; b=ufJntv3PLcmf7OR4PMV5Ix/ChwqvyYAAAPOFHAFkHOxCK8kQq6X61snISw6gpfamRKeOEM IPHu2FK0vz0h2rpehy/uE/Q83HTbe/oA02JW9/UERlpeqNBJC0GlRsfxnLr454Blh0daBc VJyaDwdZWqixaVMpmWtq5HuYgfctKDE= From: Fuad Tabba To: kvm@vger.kernel.org Cc: kvmarm@lists.linux.dev, Will Deacon , Alexandru Elisei , Suzuki K Poulose , Andre Przywara , Oliver Upton , Marc Zyngier , Fuad Tabba Subject: [PATCH kvmtool v2 3/4] Add support for registering guest_memfd-backed memory regions Date: Wed, 8 Jul 2026 19:25:09 +0100 Message-Id: <20260708182510.2181857-4-fuad.tabba@linux.dev> In-Reply-To: <20260708182510.2181857-1-fuad.tabba@linux.dev> References: <20260708182510.2181857-1-fuad.tabba@linux.dev> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT Extend kvm__register_mem() with a guest_memfd file descriptor and offset. A bank with a guest_memfd is registered with KVM_SET_USER_MEMORY_REGION2 and KVM_MEM_GUEST_MEMFD, binding the memslot to the file. This prepares for backing guest RAM with guest_memfd on arm64. Signed-off-by: Fuad Tabba --- hw/cfi_flash.c | 2 +- include/kvm/kvm.h | 15 +++++++++++++-- kvm.c | 36 ++++++++++++++++++++++++++---------- 3 files changed, 40 insertions(+), 13 deletions(-) diff --git a/hw/cfi_flash.c b/hw/cfi_flash.c index b68d9e0..4413955 100644 --- a/hw/cfi_flash.c +++ b/hw/cfi_flash.c @@ -451,7 +451,7 @@ static int map_flash_memory(struct kvm *kvm, struct cfi_flash_device *sfdev) int ret; ret = kvm__register_mem(kvm, sfdev->base_addr, sfdev->size, - sfdev->flash_memory, + sfdev->flash_memory, -1, 0, KVM_MEM_TYPE_RAM | KVM_MEM_TYPE_READONLY); if (!ret) sfdev->is_mapped = true; diff --git a/include/kvm/kvm.h b/include/kvm/kvm.h index eb23e2f..5e7b5eb 100644 --- a/include/kvm/kvm.h +++ b/include/kvm/kvm.h @@ -128,11 +128,22 @@ bool kvm__emulate_io(struct kvm_cpu *vcpu, u16 port, void *data, int direction, bool kvm__emulate_mmio(struct kvm_cpu *vcpu, u64 phys_addr, u8 *data, u32 len, u8 is_write); int kvm__destroy_mem(struct kvm *kvm, u64 guest_phys, u64 size, void *userspace_addr); int kvm__register_mem(struct kvm *kvm, u64 guest_phys, u64 size, void *userspace_addr, + int guest_memfd, u64 guest_memfd_offset, enum kvm_mem_type type); static inline int kvm__register_ram(struct kvm *kvm, u64 guest_phys, u64 size, void *userspace_addr) { return kvm__register_mem(kvm, guest_phys, size, userspace_addr, + -1, 0, KVM_MEM_TYPE_RAM); +} + +static inline int kvm__register_ram_guest_memfd(struct kvm *kvm, u64 guest_phys, + u64 size, void *userspace_addr, + int guest_memfd, + u64 guest_memfd_offset) +{ + return kvm__register_mem(kvm, guest_phys, size, userspace_addr, + guest_memfd, guest_memfd_offset, KVM_MEM_TYPE_RAM); } @@ -140,13 +151,13 @@ static inline int kvm__register_dev_mem(struct kvm *kvm, u64 guest_phys, u64 size, void *userspace_addr) { return kvm__register_mem(kvm, guest_phys, size, userspace_addr, - KVM_MEM_TYPE_DEVICE); + -1, 0, KVM_MEM_TYPE_DEVICE); } static inline int kvm__reserve_mem(struct kvm *kvm, u64 guest_phys, u64 size) { return kvm__register_mem(kvm, guest_phys, size, NULL, - KVM_MEM_TYPE_RESERVED); + -1, 0, KVM_MEM_TYPE_RESERVED); } int __must_check kvm__register_iotrap(struct kvm *kvm, u64 phys_addr, u64 len, diff --git a/kvm.c b/kvm.c index 95ccfcb..947721b 100644 --- a/kvm.c +++ b/kvm.c @@ -237,9 +237,9 @@ out: } int kvm__register_mem(struct kvm *kvm, u64 guest_phys, u64 size, - void *userspace_addr, enum kvm_mem_type type) + void *userspace_addr, int guest_memfd, + u64 guest_memfd_offset, enum kvm_mem_type type) { - struct kvm_userspace_memory_region mem; struct kvm_mem_bank *merged = NULL; struct kvm_mem_bank *bank; struct list_head *prev_entry; @@ -320,15 +320,31 @@ int kvm__register_mem(struct kvm *kvm, u64 guest_phys, u64 size, flags |= KVM_MEM_READONLY; if (type != KVM_MEM_TYPE_RESERVED) { - mem = (struct kvm_userspace_memory_region) { - .slot = slot, - .flags = flags, - .guest_phys_addr = guest_phys, - .memory_size = size, - .userspace_addr = (unsigned long)userspace_addr, - }; + if (guest_memfd >= 0) { + struct kvm_userspace_memory_region2 mem2 = { + .slot = slot, + .flags = flags | KVM_MEM_GUEST_MEMFD, + .guest_phys_addr = guest_phys, + .memory_size = size, + .userspace_addr = (unsigned long)userspace_addr, + .guest_memfd = guest_memfd, + .guest_memfd_offset = guest_memfd_offset, + }; - ret = ioctl(kvm->vm_fd, KVM_SET_USER_MEMORY_REGION, &mem); + ret = ioctl(kvm->vm_fd, KVM_SET_USER_MEMORY_REGION2, + &mem2); + } else { + struct kvm_userspace_memory_region mem = { + .slot = slot, + .flags = flags, + .guest_phys_addr = guest_phys, + .memory_size = size, + .userspace_addr = (unsigned long)userspace_addr, + }; + + ret = ioctl(kvm->vm_fd, KVM_SET_USER_MEMORY_REGION, + &mem); + } if (ret < 0) { ret = -errno; goto out; -- 2.39.5