| Message ID | 20211221151125.19446-1-chao.p.peng@linux.intel.com (mailing list archive) |
|---|---|
| Headers | show |
| Series | KVM: mm: fd-based approach for supporting KVM guest private memory | expand |
On Tue, Dec 21, 2021, Chao Peng wrote: > This is the third version of this series which try to implement the > fd-based KVM guest private memory. ... > Test > ---- > This code has been tested with latest TDX code patches hosted at > (https://github.com/intel/tdx/tree/kvm-upstream) with minimal TDX > adaption and QEMU support. > > Example QEMU command line: > -object tdx-guest,id=tdx \ > -object memory-backend-memfd-private,id=ram1,size=2G \ > -machine q35,kvm-type=tdx,pic=no,kernel_irqchip=split,memory-encryption=tdx,memory-backend=ram1 > > Changelog > ---------- > v3: > - Added locking protection when calling > invalidate_page_range/fallocate callbacks. > - Changed memslot structure to keep use useraddr for shared memory. > - Re-organized F_SEAL_INACCESSIBLE and MEMFD_OPS. > - Added MFD_INACCESSIBLE flag to force F_SEAL_INACCESSIBLE. > - Commit message improvement. > - Many small fixes for comments from the last version. Can you rebase on top of kvm/queue and send a new version? There's a massive overhaul of KVM's memslots code that's queued for 5.17, and the KVM core changes in this series conflict mightily. It's ok if the private memslot support isn't tested exactly as-is, it's not like any of us reviewers can test it anyways, but I would like to be able to apply cleanly and verify that the series doesn't break existing functionality. This version also appears to be based on an internal development branch, e.g. patch 12/15 has some bits from the TDX series. @@ -336,6 +348,7 @@ struct kvm_tdx_exit { #define KVM_EXIT_X86_BUS_LOCK 33 #define KVM_EXIT_XEN 34 #define KVM_EXIT_RISCV_SBI 35 +#define KVM_EXIT_MEMORY_ERROR 36 #define KVM_EXIT_TDX 50 /* dump number to avoid conflict. */ /* For KVM_EXIT_INTERNAL_ERROR */ @@ -554,6 +567,8 @@ struct kvm_run { unsigned long args[6]; unsigned long ret[2]; } riscv_sbi; + /* KVM_EXIT_MEMORY_ERROR */ + struct kvm_memory_exit mem; /* KVM_EXIT_TDX_VMCALL */ struct kvm_tdx_exit tdx; /* Fix the size of the union. */
On Tue, Dec 21, 2021 at 03:44:40PM +0000, Sean Christopherson wrote: > On Tue, Dec 21, 2021, Chao Peng wrote: > > This is the third version of this series which try to implement the > > fd-based KVM guest private memory. > > ... > > > Test > > ---- > > This code has been tested with latest TDX code patches hosted at > > (https://github.com/intel/tdx/tree/kvm-upstream) with minimal TDX > > adaption and QEMU support. > > > > Example QEMU command line: > > -object tdx-guest,id=tdx \ > > -object memory-backend-memfd-private,id=ram1,size=2G \ > > -machine q35,kvm-type=tdx,pic=no,kernel_irqchip=split,memory-encryption=tdx,memory-backend=ram1 > > > > Changelog > > ---------- > > v3: > > - Added locking protection when calling > > invalidate_page_range/fallocate callbacks. > > - Changed memslot structure to keep use useraddr for shared memory. > > - Re-organized F_SEAL_INACCESSIBLE and MEMFD_OPS. > > - Added MFD_INACCESSIBLE flag to force F_SEAL_INACCESSIBLE. > > - Commit message improvement. > > - Many small fixes for comments from the last version. > > Can you rebase on top of kvm/queue and send a new version? There's a massive > overhaul of KVM's memslots code that's queued for 5.17, and the KVM core changes > in this series conflict mightily. Sure, will do the rebase and send a new version. > > It's ok if the private memslot support isn't tested exactly as-is, it's not like > any of us reviewers can test it anyways, but I would like to be able to apply > cleanly and verify that the series doesn't break existing functionality. Good, it will ease me if that is acceptable (e.g. test on the relative new TDX codebase but send out the patch on latest kvm/queue which is not verified for the new function). This gets rid of the 'chicken and egg' dependency between this series and TDX patchset. > > This version also appears to be based on an internal development branch, e.g. patch > 12/15 has some bits from the TDX series. Right, it's based on latest TDX code https://github.com/intel/tdx/tree/kvm-upstream. I did this because this is the only way I can test the code. Thanks, Chao > > @@ -336,6 +348,7 @@ struct kvm_tdx_exit { > #define KVM_EXIT_X86_BUS_LOCK 33 > #define KVM_EXIT_XEN 34 > #define KVM_EXIT_RISCV_SBI 35 > +#define KVM_EXIT_MEMORY_ERROR 36 > #define KVM_EXIT_TDX 50 /* dump number to avoid conflict. */ > > /* For KVM_EXIT_INTERNAL_ERROR */ > @@ -554,6 +567,8 @@ struct kvm_run { > unsigned long args[6]; > unsigned long ret[2]; > } riscv_sbi; > + /* KVM_EXIT_MEMORY_ERROR */ > + struct kvm_memory_exit mem; > /* KVM_EXIT_TDX_VMCALL */ > struct kvm_tdx_exit tdx; > /* Fix the size of the union. */
This is the third version of this series which try to implement the fd-based KVM guest private memory. In general this patch series introduce fd-based memslot which provide guest memory through a memfd file descriptor fd[offset,size] instead of hva/size. The fd then can be created from a supported memory filesystem like tmpfs/hugetlbfs etc which we refer as memory backend. KVM and the memory backend exchange some callbacks when such memslot gets created. At runtime KVM will call into callbacks provided by backend to get the pfn with the fd+offset. Memory backend will also call into KVM callbacks when userspace fallocate/punch hole on the fd to notify KVM to map/unmap secondary MMU page tables. Comparing to existing hva-based memslot, this new type of memslot allow guest memory unmapped from host userspace like QEMU and even the kernel itself, therefore reduce attack surface and prevent userspace bugs. Based on this fd-based memslot, we can build guest private memory that is going to be used in confidential computing environments such as Intel TDX and AMD SEV. When supported, the memory backend can provide more enforcement on the fd and KVM can use a single memslot to hold both the private and shared part of the guest memory. Memfd/shmem extension --------------------- Introduces new MFD_INACCESSIBLE flag for memfd_create(), the file created with this flag cannot read(), write() or mmap() etc. In addition, two sets of callbacks are introduced as new MEMFD_OPS: - memfd_falloc_notifier: memfd -> KVM notifier when memory gets allocated/invalidated through fallocate(). - memfd_pfn_ops: kvm -> memfd to get a pfn with the fd+offset. Memslot extension ----------------- Add the private fd and the offset into the fd to existing 'shared' memslot so that both private/shared guest memory can live in one single memslot. A page in the memslot is either private or shared. A page is private only when it's already allocated in the backend fd, all the other cases it's treated as shared, this includes those already mapped as shared as well as those having not been mapped. This means the memory backend is the place which tells the truth of which page is private. Private memory map/unmap and conversion --------------------------------------- Userspace's map/unmap operations are done by fallocate() ioctl on the backend fd. - map: default fallocate() with mode=0. - unmap: fallocate() with FALLOC_FL_PUNCH_HOLE. The map/unmap will trigger above memfd_falloc_notifier to let KVM map/unmap second MMU page tables. Test ---- This code has been tested with latest TDX code patches hosted at (https://github.com/intel/tdx/tree/kvm-upstream) with minimal TDX adaption and QEMU support. Example QEMU command line: -object tdx-guest,id=tdx \ -object memory-backend-memfd-private,id=ram1,size=2G \ -machine q35,kvm-type=tdx,pic=no,kernel_irqchip=split,memory-encryption=tdx,memory-backend=ram1 Changelog ---------- v3: - Added locking protection when calling invalidate_page_range/fallocate callbacks. - Changed memslot structure to keep use useraddr for shared memory. - Re-organized F_SEAL_INACCESSIBLE and MEMFD_OPS. - Added MFD_INACCESSIBLE flag to force F_SEAL_INACCESSIBLE. - Commit message improvement. - Many small fixes for comments from the last version. Links of previous discussions ----------------------------- [1] https://lkml.kernel.org/kvm/51a6f74f-6c05-74b9-3fd7-b7cd900fb8cc@redhat.com/ [2] https://lkml.kernel.org/linux-fsdevel/20211111141352.26311-1-chao.p.peng@linux.intel.com/ Chao Peng (13): mm/memfd: Introduce MFD_INACCESSIBLE flag KVM: Extend the memslot to support fd-based private memory KVM: Implement fd-based memory using MEMFD_OPS interfaces KVM: Refactor hva based memory invalidation code KVM: Special handling for fd-based memory invalidation KVM: Split out common memory invalidation code KVM: Implement fd-based memory invalidation KVM: Add kvm_map_gfn_range KVM: Implement fd-based memory fallocation KVM: Add KVM_EXIT_MEMORY_ERROR exit KVM: Handle page fault for private memory KVM: Use kvm_userspace_memory_region_ext KVM: Register/unregister private memory slot to memfd Kirill A. Shutemov (2): mm/shmem: Introduce F_SEAL_INACCESSIBLE mm/memfd: Introduce MEMFD_OPS arch/arm64/kvm/mmu.c | 14 +- arch/mips/kvm/mips.c | 14 +- arch/powerpc/include/asm/kvm_ppc.h | 28 ++-- arch/powerpc/kvm/book3s.c | 14 +- arch/powerpc/kvm/book3s_hv.c | 14 +- arch/powerpc/kvm/book3s_pr.c | 14 +- arch/powerpc/kvm/booke.c | 14 +- arch/powerpc/kvm/powerpc.c | 14 +- arch/riscv/kvm/mmu.c | 14 +- arch/s390/kvm/kvm-s390.c | 14 +- arch/x86/kvm/Kconfig | 1 + arch/x86/kvm/Makefile | 3 +- arch/x86/kvm/mmu/mmu.c | 112 +++++++++++++- arch/x86/kvm/mmu/paging_tmpl.h | 11 +- arch/x86/kvm/x86.c | 16 +- include/linux/kvm_host.h | 57 +++++-- include/linux/memfd.h | 22 +++ include/linux/shmem_fs.h | 16 ++ include/uapi/linux/fcntl.h | 1 + include/uapi/linux/kvm.h | 27 ++++ include/uapi/linux/memfd.h | 1 + mm/Kconfig | 4 + mm/memfd.c | 33 +++- mm/shmem.c | 195 ++++++++++++++++++++++- virt/kvm/kvm_main.c | 239 +++++++++++++++++++++-------- virt/kvm/memfd.c | 100 ++++++++++++ 26 files changed, 822 insertions(+), 170 deletions(-) create mode 100644 virt/kvm/memfd.c