Re: [RFC PATCH v2 09/44] target/i386: kvm: don't synchronize guest tsc for TD guest

[Connor Kuehl]

On 7/7/21 7:54 PM, isaku.yamahata@gmail.com wrote:
> From: Isaku Yamahata <isaku.yamahata@intel.com>
>
> Make kvm_synchronize_all_tsc() nop for TD-guest.

s/nop/noop

> TDX module specification, 9.11.1 TSC Virtualization

This appears in 9.12.1 of the latest revision as of this writing.

https://software.intel.com/content/dam/develop/external/us/en/documents/tdx-module-1eas-v0.85.039.pdf

> "Virtual TSC values are consistent among all the TD;s VCPUs at the

s/TD;s/TDs

> level suppored by the CPU".

s/suppored/supported

> There is no need for qemu to synchronize tsc and VMM can't access
> to guest TSC. Actually do_kvm_synchronize_tsc() hits assert due to
> failure to write to guest tsc.
>
> > qemu/target/i386/kvm.c:235: kvm_get_tsc: Assertion `ret == 1' failed.
>
> Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com>

Reviewed-by: Connor Kuehl <ckuehl@redhat.com>