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SubjectRe: [PATCH] x86/tsx: clear RTM and HLE when MSR_IA32_TSX_CTRL is not supported
On Mon, Sep 06, 2021 at 10:46:05AM +0800, Hao Peng wrote:
> If hypervisor does not support MSR_IA32_TSX_CTRL, but guest supports
> RTM and HLE features, it will affect TAA mitigation.
>
> Signed-off-by: Peng Hao <flyingpeng@tencent.com>
> ---
> arch/x86/kernel/cpu/tsx.c | 7 +++++++
> 1 file changed, 7 insertions(+)
>
> diff --git a/arch/x86/kernel/cpu/tsx.c b/arch/x86/kernel/cpu/tsx.c
> index 9c7a5f049292..5e852c14fef2 100644
> --- a/arch/x86/kernel/cpu/tsx.c
> +++ b/arch/x86/kernel/cpu/tsx.c
> @@ -122,6 +122,13 @@ void __init tsx_init(void)
>
> if (!tsx_ctrl_is_supported()) {
> tsx_ctrl_state = TSX_CTRL_NOT_SUPPORTED;
> +
> + /* If hypervisor does not support MSR_IA32_TSX_CTRL emulation,
> + * but guest supports RTM and HLE features, it will affect TAA
> + * (tsx_async_abort)mitigation.
> + */
> + setup_clear_cpu_cap(X86_FEATURE_RTM);
> + setup_clear_cpu_cap(X86_FEATURE_HLE);
> return;
> }

How does that even happen - the hypervisor does not support the MSR but
"guest supports" TSX features?!

I guess the guest is detecting it wrong.

What hypervisor, what guest, how do I reproduce?

Please give full details.

--
Regards/Gruss,
Boris.

https://people.kernel.org/tglx/notes-about-netiquette

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