linux-kernel - Re: [PATCH 4/9] x86/virt/tdx: Abstract reading multiple global metadata fields as a helper

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Message-ID: <2af34675563cf78db0d17d8d5af3d7160c82cd94.camel@intel.com>
Date: Tue, 18 Jun 2024 23:42:29 +0000
From: "Huang, Kai" <kai.huang@...el.com>
To: "nik.borisov@...e.com" <nik.borisov@...e.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC: "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>, "Hansen, Dave"
	<dave.hansen@...el.com>, "bp@...en8.de" <bp@...en8.de>, "x86@...nel.org"
	<x86@...nel.org>, "peterz@...radead.org" <peterz@...radead.org>,
	"hpa@...or.com" <hpa@...or.com>, "mingo@...hat.com" <mingo@...hat.com>,
	"Williams, Dan J" <dan.j.williams@...el.com>,
	"kirill.shutemov@...ux.intel.com" <kirill.shutemov@...ux.intel.com>,
	"pbonzini@...hat.com" <pbonzini@...hat.com>, "tglx@...utronix.de"
	<tglx@...utronix.de>, "seanjc@...gle.com" <seanjc@...gle.com>,
	"kvm@...r.kernel.org" <kvm@...r.kernel.org>, "binbin.wu@...ux.intel.com"
	<binbin.wu@...ux.intel.com>, "Yamahata, Isaku" <isaku.yamahata@...el.com>
Subject: Re: [PATCH 4/9] x86/virt/tdx: Abstract reading multiple global
 metadata fields as a helper

On Tue, 2024-06-18 at 14:45 +0300, Nikolay Borisov wrote:
> 
> On 16.06.24 г. 15:01 ч., Kai Huang wrote:
> > For now the kernel only reads "TD Memory Region" (TDMR) related global
> > metadata fields to a 'struct tdx_tdmr_sysinfo' for initializing the TDX
> > module.  Future changes will need to read other metadata fields that
> > don't make sense to populate to the "struct tdx_tdmr_sysinfo".
> > 
> > Now the code in get_tdx_tdmr_sysinfo() to read multiple global metadata
> > fields is not bound to the 'struct tdx_tdmr_sysinfo', and can support
> > reading all metadata element sizes.  Abstract this code as a helper for
> > future use.
> > 
> > Signed-off-by: Kai Huang <kai.huang@...el.com>
> > ---
> >   arch/x86/virt/vmx/tdx/tdx.c | 27 ++++++++++++++++-----------
> >   1 file changed, 16 insertions(+), 11 deletions(-)
> > 
> > diff --git a/arch/x86/virt/vmx/tdx/tdx.c b/arch/x86/virt/vmx/tdx/tdx.c
> > index 4392e82a9bcb..c68fbaf4aa15 100644
> > --- a/arch/x86/virt/vmx/tdx/tdx.c
> > +++ b/arch/x86/virt/vmx/tdx/tdx.c
> > @@ -304,6 +304,21 @@ struct field_mapping {
> >   	  .offset   = offsetof(_struct, _member),		\
> >   	  .size	    = sizeof(typeof(((_struct *)0)->_member)) }
> >   
> > +static int stbuf_read_sysmd_multi(const struct field_mapping *fields,
> 
> Rename it to read_system_metadata_fields i.e just use the plural form of 
> the single field function. Whatever you choose to rename the singular 
> form, just make this function be the plural. But as a general remark - I 
> don't see what value the "stbuf" prefix brings. 'sysmd' is also somewhat 
> unintuitive. Any of 
> read_metadata_fields/read_sys_metadata_fields/read_system_metadata_fields 
> seem better.

read_sys_metadata_field() vs read_sys_metadata_fields() is hard to
distinguish due to there's only one character difference.  This is one
reason I added "stbuf" prefix hoping to make it more clear that this
function reads multiple fields to a buffer of a structure.

In terms of "sysmd" I just wanted to make the function name shorter.  This
function is only used by tdx.c internally so I think it's fine.

Anyway I am open on this.  Let's wait for some more time to see whether
other people have comments or not.