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Linux kernel source tree
adafea1106
Add guest_tsc_protected member to struct kvm_arch_vcpu and prohibit changing TSC offset/multiplier when guest_tsc_protected is true. X86 confidential computing technology defines protected guest TSC so that the VMM can't change the TSC offset/multiplier once vCPU is initialized. SEV-SNP defines Secure TSC as optional, whereas TDX mandates it. KVM has common logic on x86 that tries to guess or adjust TSC offset/multiplier for better guest TSC and TSC interrupt latency at KVM vCPU creation (kvm_arch_vcpu_postcreate()), vCPU migration over pCPU (kvm_arch_vcpu_load()), vCPU TSC device attributes (kvm_arch_tsc_set_attr()) and guest/host writing to TSC or TSC adjust MSR (kvm_set_msr_common()). The current x86 KVM implementation conflicts with protected TSC because the VMM can't change the TSC offset/multiplier. Because KVM emulates the TSC timer or the TSC deadline timer with the TSC offset/multiplier, the TSC timer interrupts is injected to the guest at the wrong time if the KVM TSC offset is different from what the TDX module determined. Originally this issue was found by cyclic test of rt-test [1] as the latency in TDX case is worse than VMX value + TDX SEAMCALL overhead. It turned out that the KVM TSC offset is different from what the TDX module determines. Disable or ignore the KVM logic to change/adjust the TSC offset/multiplier somehow, thus keeping the KVM TSC offset/multiplier the same as the value of the TDX module. Writes to MSR_IA32_TSC are also blocked as they amount to a change in the TSC offset. [1] https://git.kernel.org/pub/scm/utils/rt-tests/rt-tests.git Reported-by: Marcelo Tosatti <mtosatti@redhat.com> Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com> Message-ID: <3a7444aec08042fe205666864b6858910e86aa98.1728719037.git.isaku.yamahata@intel.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> |
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| 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.