mirror of
https://github.com/torvalds/linux.git
synced 2026-07-29 02:31:27 +02:00
Linux kernel source tree
bb723bebde
Handle TDX PV MMIO hypercall when TDX guest calls TDVMCALL with the leaf #VE.RequestMMIO (same value as EXIT_REASON_EPT_VIOLATION) according to TDX Guest Host Communication Interface (GHCI) spec. For TDX guests, VMM is not allowed to access vCPU registers and the private memory, and the code instructions must be fetched from the private memory. So MMIO emulation implemented for non-TDX VMs is not possible for TDX guests. In TDX the MMIO regions are instead configured by VMM to trigger a #VE exception in the guest. The #VE handling is supposed to emulate the MMIO instruction inside the guest and convert it into a TDVMCALL with the leaf #VE.RequestMMIO, which equals to EXIT_REASON_EPT_VIOLATION. The requested MMIO address must be in shared GPA space. The shared bit is stripped after check because the existing code for MMIO emulation is not aware of the shared bit. The MMIO GPA shouldn't have a valid memslot, also the attribute of the GPA should be shared. KVM could do the checks before exiting to userspace, however, even if KVM does the check, there still will be race conditions between the check in KVM and the emulation of MMIO access in userspace due to a memslot hotplug, or a memory attribute conversion. If userspace doesn't check the attribute of the GPA and the attribute happens to be private, it will not pose a security risk or cause an MCE, but it can lead to another issue. E.g., in QEMU, treating a GPA with private attribute as shared when it falls within RAM's range can result in extra memory consumption during the emulation to the access to the HVA of the GPA. There are two options: 1) Do the check both in KVM and userspace. 2) Do the check only in QEMU. This patch chooses option 2, i.e. KVM omits the memslot and attribute checks, and expects userspace to do the checks. Similar to normal MMIO emulation, try to handle the MMIO in kernel first, if kernel can't support it, forward the request to userspace. Export needed symbols used for MMIO handling. Fragments handling is not needed for TDX PV MMIO because GPA is provided, if a MMIO access crosses page boundary, it should be continuous in GPA. Also, the size is limited to 1, 2, 4, 8 bytes. No further split needed. Allow cross page access because no extra handling needed after checking both start and end GPA are shared GPAs. Suggested-by: Sean Christopherson <seanjc@google.com> Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com> Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com> Co-developed-by: Binbin Wu <binbin.wu@linux.intel.com> Signed-off-by: Binbin Wu <binbin.wu@linux.intel.com> Reviewed-by: Paolo Bonzini <pbonzini@redhat.com> Message-ID: <20250222014225.897298-10-binbin.wu@linux.intel.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> |
||
|---|---|---|
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| io_uring | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| rust | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .clippy.toml | ||
| .cocciconfig | ||
| .editorconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| .rustfmt.toml | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.