| Message ID | 20250527180245.1413463-9-tabba@google.com |
|---|---|
| State | New |
| Headers | show |
| Series | KVM: Mapping guest_memfd backed memory at the host for software protected VMs | expand |
Hi Fuad,
kernel test robot noticed the following build errors:
[auto build test ERROR on 0ff41df1cb268fc69e703a08a57ee14ae967d0ca]
url: https://github.com/intel-lab-lkp/linux/commits/Fuad-Tabba/KVM-Rename-CONFIG_KVM_PRIVATE_MEM-to-CONFIG_KVM_GMEM/20250528-020608
base: 0ff41df1cb268fc69e703a08a57ee14ae967d0ca
patch link: https://lore.kernel.org/r/20250527180245.1413463-9-tabba%40google.com
patch subject: [PATCH v10 08/16] KVM: guest_memfd: Allow host to map guest_memfd pages
config: powerpc-allmodconfig (https://download.01.org/0day-ci/archive/20250529/202505290736.HR4GYiOF-lkp@intel.com/config)
compiler: powerpc64-linux-gcc (GCC) 14.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250529/202505290736.HR4GYiOF-lkp@intel.com/reproduce)
If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202505290736.HR4GYiOF-lkp@intel.com/
All errors (new ones prefixed by >>):
arch/powerpc/kvm/../../../virt/kvm/guest_memfd.c: In function '__kvm_gmem_create':
arch/powerpc/kvm/../../../virt/kvm/guest_memfd.c:487:14: error: implicit declaration of function 'get_unused_fd_flags' [-Wimplicit-function-declaration]
487 | fd = get_unused_fd_flags(0);
| ^~~~~~~~~~~~~~~~~~~
arch/powerpc/kvm/../../../virt/kvm/guest_memfd.c:524:9: error: implicit declaration of function 'fd_install'; did you mean 'fs_initcall'? [-Wimplicit-function-declaration]
524 | fd_install(fd, file);
| ^~~~~~~~~~
| fs_initcall
arch/powerpc/kvm/../../../virt/kvm/guest_memfd.c:530:9: error: implicit declaration of function 'put_unused_fd'; did you mean 'put_user_ns'? [-Wimplicit-function-declaration]
530 | put_unused_fd(fd);
| ^~~~~~~~~~~~~
| put_user_ns
arch/powerpc/kvm/../../../virt/kvm/guest_memfd.c: In function 'kvm_gmem_create':
>> arch/powerpc/kvm/../../../virt/kvm/guest_memfd.c:540:13: error: implicit declaration of function 'kvm_arch_supports_gmem_shared_mem' [-Wimplicit-function-declaration]
540 | if (kvm_arch_supports_gmem_shared_mem(kvm))
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
arch/powerpc/kvm/../../../virt/kvm/guest_memfd.c: In function 'kvm_gmem_bind':
arch/powerpc/kvm/../../../virt/kvm/guest_memfd.c:564:16: error: implicit declaration of function 'fget'; did you mean 'sget'? [-Wimplicit-function-declaration]
564 | file = fget(fd);
| ^~~~
| sget
arch/powerpc/kvm/../../../virt/kvm/guest_memfd.c:564:14: error: assignment to 'struct file *' from 'int' makes pointer from integer without a cast [-Wint-conversion]
564 | file = fget(fd);
| ^
arch/powerpc/kvm/../../../virt/kvm/guest_memfd.c:614:9: error: implicit declaration of function 'fput'; did you mean 'iput'? [-Wimplicit-function-declaration]
614 | fput(file);
| ^~~~
| iput
vim +/kvm_arch_supports_gmem_shared_mem +540 arch/powerpc/kvm/../../../virt/kvm/guest_memfd.c
533
534 int kvm_gmem_create(struct kvm *kvm, struct kvm_create_guest_memfd *args)
535 {
536 loff_t size = args->size;
537 u64 flags = args->flags;
538 u64 valid_flags = 0;
539
> 540 if (kvm_arch_supports_gmem_shared_mem(kvm))
541 valid_flags |= GUEST_MEMFD_FLAG_SUPPORT_SHARED;
542
543 if (flags & ~valid_flags)
544 return -EINVAL;
545
546 if (size <= 0 || !PAGE_ALIGNED(size))
547 return -EINVAL;
548
549 return __kvm_gmem_create(kvm, size, flags);
550 }
551
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h index 709cc2a7ba66..ce9ad4cd93c5 100644 --- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -2255,8 +2255,18 @@ void kvm_configure_mmu(bool enable_tdp, int tdp_forced_root_level, #ifdef CONFIG_KVM_GMEM #define kvm_arch_supports_gmem(kvm) ((kvm)->arch.supports_gmem) + +/* + * CoCo VMs with hardware support that use guest_memfd only for backing private + * memory, e.g., TDX, cannot use guest_memfd with userspace mapping enabled. + */ +#define kvm_arch_supports_gmem_shared_mem(kvm) \ + (IS_ENABLED(CONFIG_KVM_GMEM_SHARED_MEM) && \ + ((kvm)->arch.vm_type == KVM_X86_SW_PROTECTED_VM || \ + (kvm)->arch.vm_type == KVM_X86_DEFAULT_VM)) #else #define kvm_arch_supports_gmem(kvm) false +#define kvm_arch_supports_gmem_shared_mem(kvm) false #endif #define kvm_arch_has_readonly_mem(kvm) (!(kvm)->arch.has_protected_state) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 035ced06b2dd..2a02f2457c42 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -12718,7 +12718,8 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type) return -EINVAL; kvm->arch.vm_type = type; - kvm->arch.supports_gmem = (type == KVM_X86_SW_PROTECTED_VM); + kvm->arch.supports_gmem = + type == KVM_X86_DEFAULT_VM || type == KVM_X86_SW_PROTECTED_VM; /* Decided by the vendor code for other VM types. */ kvm->arch.pre_fault_allowed = type == KVM_X86_DEFAULT_VM || type == KVM_X86_SW_PROTECTED_VM; diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h index 80371475818f..ba83547e62b0 100644 --- a/include/linux/kvm_host.h +++ b/include/linux/kvm_host.h @@ -729,6 +729,19 @@ static inline bool kvm_arch_supports_gmem(struct kvm *kvm) } #endif +/* + * Returns true if this VM supports shared mem in guest_memfd. + * + * Arch code must define kvm_arch_supports_gmem_shared_mem if support for + * guest_memfd is enabled. + */ +#if !defined(kvm_arch_supports_gmem_shared_mem) && !IS_ENABLED(CONFIG_KVM_GMEM) +static inline bool kvm_arch_supports_gmem_shared_mem(struct kvm *kvm) +{ + return false; +} +#endif + #ifndef kvm_arch_has_readonly_mem static inline bool kvm_arch_has_readonly_mem(struct kvm *kvm) { diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h index b6ae8ad8934b..c2714c9d1a0e 100644 --- a/include/uapi/linux/kvm.h +++ b/include/uapi/linux/kvm.h @@ -1566,6 +1566,7 @@ struct kvm_memory_attributes { #define KVM_MEMORY_ATTRIBUTE_PRIVATE (1ULL << 3) #define KVM_CREATE_GUEST_MEMFD _IOWR(KVMIO, 0xd4, struct kvm_create_guest_memfd) +#define GUEST_MEMFD_FLAG_SUPPORT_SHARED (1ULL << 0) struct kvm_create_guest_memfd { __u64 size; diff --git a/virt/kvm/Kconfig b/virt/kvm/Kconfig index 559c93ad90be..df225298ab10 100644 --- a/virt/kvm/Kconfig +++ b/virt/kvm/Kconfig @@ -128,3 +128,8 @@ config HAVE_KVM_ARCH_GMEM_PREPARE config HAVE_KVM_ARCH_GMEM_INVALIDATE bool depends on KVM_GMEM + +config KVM_GMEM_SHARED_MEM + select KVM_GMEM + bool + prompt "Enable support for non-private (shared) memory in guest_memfd" diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c index 6db515833f61..5d34712f64fc 100644 --- a/virt/kvm/guest_memfd.c +++ b/virt/kvm/guest_memfd.c @@ -312,7 +312,81 @@ static pgoff_t kvm_gmem_get_index(struct kvm_memory_slot *slot, gfn_t gfn) return gfn - slot->base_gfn + slot->gmem.pgoff; } +static bool kvm_gmem_supports_shared(struct inode *inode) +{ + u64 flags; + + if (!IS_ENABLED(CONFIG_KVM_GMEM_SHARED_MEM)) + return false; + + flags = (u64)inode->i_private; + + return flags & GUEST_MEMFD_FLAG_SUPPORT_SHARED; +} + + +#ifdef CONFIG_KVM_GMEM_SHARED_MEM +static vm_fault_t kvm_gmem_fault_shared(struct vm_fault *vmf) +{ + struct inode *inode = file_inode(vmf->vma->vm_file); + struct folio *folio; + vm_fault_t ret = VM_FAULT_LOCKED; + + folio = kvm_gmem_get_folio(inode, vmf->pgoff); + if (IS_ERR(folio)) { + int err = PTR_ERR(folio); + + if (err == -EAGAIN) + return VM_FAULT_RETRY; + + return vmf_error(err); + } + + if (WARN_ON_ONCE(folio_test_large(folio))) { + ret = VM_FAULT_SIGBUS; + goto out_folio; + } + + if (!folio_test_uptodate(folio)) { + clear_highpage(folio_page(folio, 0)); + kvm_gmem_mark_prepared(folio); + } + + vmf->page = folio_file_page(folio, vmf->pgoff); + +out_folio: + if (ret != VM_FAULT_LOCKED) { + folio_unlock(folio); + folio_put(folio); + } + + return ret; +} + +static const struct vm_operations_struct kvm_gmem_vm_ops = { + .fault = kvm_gmem_fault_shared, +}; + +static int kvm_gmem_mmap(struct file *file, struct vm_area_struct *vma) +{ + if (!kvm_gmem_supports_shared(file_inode(file))) + return -ENODEV; + + if ((vma->vm_flags & (VM_SHARED | VM_MAYSHARE)) != + (VM_SHARED | VM_MAYSHARE)) { + return -EINVAL; + } + + vma->vm_ops = &kvm_gmem_vm_ops; + + return 0; +} +#else +#define kvm_gmem_mmap NULL +#endif /* CONFIG_KVM_GMEM_SHARED_MEM */ + static struct file_operations kvm_gmem_fops = { + .mmap = kvm_gmem_mmap, .open = generic_file_open, .release = kvm_gmem_release, .fallocate = kvm_gmem_fallocate, @@ -463,6 +537,9 @@ int kvm_gmem_create(struct kvm *kvm, struct kvm_create_guest_memfd *args) u64 flags = args->flags; u64 valid_flags = 0; + if (kvm_arch_supports_gmem_shared_mem(kvm)) + valid_flags |= GUEST_MEMFD_FLAG_SUPPORT_SHARED; + if (flags & ~valid_flags) return -EINVAL; @@ -501,6 +578,10 @@ int kvm_gmem_bind(struct kvm *kvm, struct kvm_memory_slot *slot, offset + size > i_size_read(inode)) goto err; + if (kvm_gmem_supports_shared(inode) && + !kvm_arch_supports_gmem_shared_mem(kvm)) + goto err; + filemap_invalidate_lock(inode->i_mapping); start = offset >> PAGE_SHIFT;