Re: [PATCH v3 06/10] x86/hyperv: Introduce a global variable hyperv_paravisor_present

[Tianyu Lan <ltykernel@gmail.com>]

On 8/24/2023 4:07 PM, Dexuan Cui wrote:
> The new variable hyperv_paravisor_present is set only when the VM
> is a SNP/TDX VM with the paravisor running: see ms_hyperv_init_platform().
> 
> We introduce hyperv_paravisor_present because we can not use
> ms_hyperv.paravisor_present in arch/x86/include/asm/mshyperv.h:
> 
> struct ms_hyperv_info is defined in include/asm-generic/mshyperv.h, which
> is included at the end of arch/x86/include/asm/mshyperv.h, but at the
> beginning of arch/x86/include/asm/mshyperv.h, we would already need to use
> struct ms_hyperv_info in hv_do_hypercall().
> 
> We use hyperv_paravisor_present only in include/asm-generic/mshyperv.h,
> and use ms_hyperv.paravisor_present elsewhere. In the future, we'll
> introduce a hypercall function structure for different VM types, and
> at boot time, the right function pointers would be written into the
> structure so that runtime testing of TDX vs. SNP vs. normal will be
> avoided and hyperv_paravisor_present will no longer be needed.
> 
> Call hv_vtom_init() when it's a VBS VM or when ms_hyperv.paravisor_present
> is true, i.e. the VM is a SNP VM or TDX VM with the paravisor.
> 
> Enhance hv_vtom_init() for a TDX VM with the paravisor.
> 
> In hv_common_cpu_init(), don't decrypt the hyperv_pcpu_input_arg
> for a TDX VM with the paravisor, just like we don't decrypt the page
> for a SNP VM with the paravisor.
> 
> Signed-off-by: Dexuan Cui <decui@microsoft.com>

Reviewed-by: Tianyu Lan <tiala@microsoft.com>