Re: [PATCH v7 07/10] x86/virt/tdx: Trim away tail null CMRs

[Dave Hansen]

On 11/11/24 02:39, Kai Huang wrote:
> TDX architecturally supports up to 32 CMRs.  The global metadata field
> "NUM_CMRS" reports the number of CMR entries that can be read by the
> kernel.  However, that field may just report the maximum number of CMRs
> albeit the actual number of CMRs is smaller, in which case there are
> tail null CMRs (size is 0).
> 
> Trim away those null CMRs, and print valid CMRs since they are useful
> at least to developers.
> 
> More information about CMR can be found at "Intel TDX ISA Background:
> Convertible Memory Ranges (CMRs)" in TDX 1.5 base spec [1], and
> "CMR_INFO" in TDX 1.5 ABI spec [2].
> 
> Now get_tdx_sys_info() just reads kernel-needed global metadata to
> kernel structure, and it is auto-generated.  Add a wrapper function
> init_tdx_sys_info() to invoke get_tdx_sys_info() and provide room to do
> additional things like dealing with CMRs.

I'm not sure I understand why this patch is here.

What does trimming buy us in the first place?