From: Anirudh Rayabharam <anrayabh@xxxxxxxxxxxxxxxxxxx> Sent: Thursday, October 27, 2022 2:57 AM
>
> hv_cleanup resets the hypercall page by setting the MSR to 0. However,
The function name is hyperv_cleanup(), not hv_cleanup().
> the root partition is not allowed to write to the GPA bits of the MSR.
> Instead, it uses the hypercall page provided by the MSR. Similar is the
> case with the reference TSC MSR.
>
> Clear only the enable bit instead of zeroing the entire MSR to make
> the code valid for root partition too.
>
> Signed-off-by: Anirudh Rayabharam <anrayabh@xxxxxxxxxxxxxxxxxxx>
> ---
> arch/x86/hyperv/hv_init.c | 11 +++++++----
> 1 file changed, 7 insertions(+), 4 deletions(-)
>
> diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
> index 29774126e931..80fdfff9266c 100644
> --- a/arch/x86/hyperv/hv_init.c
> +++ b/arch/x86/hyperv/hv_init.c
> @@ -537,6 +537,7 @@ void __init hyperv_init(void)
> void hyperv_cleanup(void)
> {
> union hv_x64_msr_hypercall_contents hypercall_msr;
> + union hv_reference_tsc_msr tsc_msr;
>
> unregister_syscore_ops(&hv_syscore_ops);
>
> @@ -552,12 +553,14 @@ void hyperv_cleanup(void)
> hv_hypercall_pg = NULL;
>
> /* Reset the hypercall page */
> - hypercall_msr.as_uint64 = 0;
> - wrmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);
> + hypercall_msr.as_uint64 = hv_get_register(HV_X64_MSR_HYPERCALL);
> + hypercall_msr.enable = 0;
> + hv_set_register(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);
>
> /* Reset the TSC page */
> - hypercall_msr.as_uint64 = 0;
> - wrmsrl(HV_X64_MSR_REFERENCE_TSC, hypercall_msr.as_uint64);
> + tsc_msr.as_uint64 = hv_get_register(HV_X64_MSR_REFERENCE_TSC);
> + tsc_msr.enable = 0;
> + hv_set_register(HV_X64_MSR_REFERENCE_TSC, tsc_msr.as_uint64);
> }
>
> void hyperv_report_panic(struct pt_regs *regs, long err, bool in_die)
> --
> 2.34.1
Modulo the nit in the commit message,
Reviewed-by: Michael Kelley <mikelley@xxxxxxxxxxxxx>
