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

["Michael Kelley (LINUX)" <mikelley@microsoft.com>]

From: Dexuan Cui <decui@microsoft.com> Sent: Thursday, August 24, 2023 1:07 AM
> 
> 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>
> ---
> 
> Changes in v2: None
> 
> Changes in v3:
>   Improved the changelog
>   Use ms_hyperv.paravisor_present in general and only use
>     hyperv_paravisor_present in arch/x86/include/asm/mshyperv.h
>   Fixed the build when CONFIG_AMD_MEM_ENCRYPT and/or
>      CONFIG_INTEL_TDX_GUEST are not set.
>   Updated arch/x86/include/asm/mshyperv.h accordingly
>   hv_vtom_init(): Fixed/added the comments
>   Handled the TDX special case directly in vmbus_set_event().
> 
>  arch/x86/hyperv/hv_init.c       |  4 ++--
>  arch/x86/hyperv/ivm.c           | 38 ++++++++++++++++++++++++++++++---
>  arch/x86/include/asm/mshyperv.h | 15 ++++++++-----
>  arch/x86/kernel/cpu/mshyperv.c  |  9 ++++++--
>  drivers/hv/connection.c         | 15 +++++++++----
>  drivers/hv/hv.c                 | 10 ++++-----
>  drivers/hv/hv_common.c          |  3 ++-
>  7 files changed, 72 insertions(+), 22 deletions(-)

Reviewed-by: Michael Kelley <mikelley@microsoft.com>