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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.002688, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 11/29/24 06:39, Nikita Kalyazin wrote: > > +#if defined(CONFIG_KVM_GENERIC_PRIVATE_MEM) && !defined(CONFIG_KVM_AMD_SEV) Another option is to use the confidential computing (coco) attributes to keep the write operation limited to clear-text guests (diff against patch 1/2): There are a couple of benefits and shortcomings that I've listed below the diff. diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c index 9aba0ba25276..b7a0c7f2f82d 100644 --- a/virt/kvm/guest_memfd.c +++ b/virt/kvm/guest_memfd.c @@ -1,5 +1,6 @@ // SPDX-License-Identifier: GPL-2.0 #include +#include #include #include #include @@ -274,7 +275,14 @@ static struct folio *kvm_gmem_get_folio(struct inode *inode, pgoff_t index) return filemap_grab_folio(inode->i_mapping, index); } -#if defined(CONFIG_KVM_GENERIC_PRIVATE_MEM) && !defined(CONFIG_KVM_AMD_SEV) +static bool kvm_has_cc(void) +{ + if (cc_platform_has(CC_ATTR_MEM_ENCRYPT)) + return true; + return false; +} + +#if defined(CONFIG_KVM_GENERIC_PRIVATE_MEM) static ssize_t kvm_kmem_gmem_write(struct file *file, const char __user *buf, size_t count, loff_t *offset) { @@ -290,6 +298,9 @@ static ssize_t kvm_kmem_gmem_write(struct file *file, const char __user *buf, if (!buf) return -EINVAL; + if (kvm_has_cc()) + return -EIO; + start = *offset >> PAGE_SHIFT; end = (*offset + count) >> PAGE_SHIFT; @@ -564,7 +575,7 @@ static pgoff_t kvm_gmem_get_index(struct kvm_memory_slot *slot, gfn_t gfn) } static struct file_operations kvm_gmem_fops = { -#if defined(CONFIG_KVM_GENERIC_PRIVATE_MEM) && !defined(CONFIG_KVM_AMD_SEV) +#if defined(CONFIG_KVM_GENERIC_PRIVATE_MEM) .llseek = default_llseek, .write = kvm_kmem_gmem_write, #endif Advantages: * works with multiple architectures (powerpc and x86 so far) * enumerates specific types of coco attributes Disadvantages: * The platform can have an encryption attribute but still be running a guest in clear text * Some guests could be encrypted while others are clear text To remedy the disadvantage, the write function would need to check if guest encryption is currently active for a specific guest. Mike > +static ssize_t kvm_kmem_gmem_write(struct file *file, const char __user *buf, > + size_t count, loff_t *offset) > +{ > + pgoff_t start, end, index; > + ssize_t ret = 0;