[RFCv2 00/13] TDX and guest memory unmapping

Kirill A. Shutemov
2021-04-16T15:41:39Z

TDX integrity check failures may lead to system shutdown host kernel must
not allow any writes to TD-private memory. This requirment clashes with
KVM design: KVM expects the guest memory to be mapped into host userspace
(e.g. QEMU).

This patchset aims to start discussion on how we can approach the issue.

The core of the change is in the last patch. Please see more detailed
description of the issue and proposoal of the solution there.

TODO:
- THP support
- Clarify semantics wrt. page cache

v2:
- Unpoison page on free
- Authorize access to the page: only the KVM that poisoned the page
allows to touch it
- FOLL_ALLOW_POISONED is implemented

The patchset can also be found here:

git://git.kernel.org/pub/scm/linux/kernel/git/kas/linux.git kvm-unmapped-poison

Kirill A. Shutemov (13):
x86/mm: Move force_dma_unencrypted() to common code
x86/kvm: Introduce KVM memory protection feature
x86/kvm: Make DMA pages shared
x86/kvm: Use bounce buffers for KVM memory protection
x86/kvmclock: Share hvclock memory with the host
x86/realmode: Share trampoline area if KVM memory protection enabled
mm: Add hwpoison_entry_to_pfn() and hwpoison_entry_to_page()
mm/gup: Add FOLL_ALLOW_POISONED
shmem: Fail shmem_getpage_gfp() on poisoned pages
mm: Keep page reference for hwpoison entries
mm: Replace hwpoison entry with present PTE if page got unpoisoned
KVM: passdown struct kvm to hva_to_pfn_slow()
KVM: unmap guest memory using poisoned pages

arch/powerpc/kvm/book3s_64_mmu_hv.c | 2 +-
arch/powerpc/kvm/book3s_64_mmu_radix.c | 2 +-
arch/x86/Kconfig | 9 +-
arch/x86/include/asm/cpufeatures.h | 1 +
arch/x86/include/asm/io.h | 4 +-
arch/x86/include/asm/kvm_para.h | 5 +
arch/x86/include/asm/mem_encrypt.h | 7 +-
arch/x86/include/uapi/asm/kvm_para.h | 3 +-
arch/x86/kernel/kvm.c | 19 +++
arch/x86/kernel/kvmclock.c | 2 +-
arch/x86/kernel/pci-swiotlb.c | 3 +-
arch/x86/kvm/Kconfig | 1 +
arch/x86/kvm/cpuid.c | 3 +-
arch/x86/kvm/mmu/mmu.c | 20 ++-
arch/x86/kvm/mmu/paging_tmpl.h | 10 +-
arch/x86/kvm/x86.c | 6 +
arch/x86/mm/Makefile | 2 +
arch/x86/mm/mem_encrypt.c | 74 ---------
arch/x86/mm/mem_encrypt_common.c | 87 ++++++++++
arch/x86/mm/pat/set_memory.c | 10 ++
arch/x86/realmode/init.c | 7 +-
include/linux/kvm_host.h | 31 +++-
include/linux/mm.h | 1 +
include/linux/swapops.h | 20 +++
include/uapi/linux/kvm_para.h | 5 +-
mm/gup.c | 29 ++--
mm/memory.c | 44 ++++-
mm/page_alloc.c | 7 +
mm/rmap.c | 2 +-
mm/shmem.c | 7 +
virt/Makefile | 2 +-
virt/kvm/Kconfig | 4 +
virt/kvm/Makefile | 1 +
virt/kvm/kvm_main.c | 212 +++++++++++++++++++------
virt/kvm/mem_protected.c | 110 +++++++++++++
35 files changed, 593 insertions(+), 159 deletions(-)
create mode 100644 arch/x86/mm/mem_encrypt_common.c
create mode 100644 virt/kvm/Makefile
create mode 100644 virt/kvm/mem_protected.c

--
2.26.3