Re: [PATCH v14 12/23] x86/virt/tdx: Allocate and set up PAMTs for TDMRs

[Nikolay Borisov]

On 24.10.23 г. 13:49 ч., Huang, Kai wrote:
> On Tue, 2023-10-24 at 08:53 +0300, Nikolay Borisov wrote:
> > On 17.10.23 г. 13:14 ч., Kai Huang wrote:
> >
> > <snip>
> >
> > >    arch/x86/Kconfig                  |   1 +
> > >    arch/x86/include/asm/shared/tdx.h |   1 +
> > >    arch/x86/virt/vmx/tdx/tdx.c       | 215 +++++++++++++++++++++++++++++-
> > >    arch/x86/virt/vmx/tdx/tdx.h       |   1 +
> > >    4 files changed, 213 insertions(+), 5 deletions(-)
> > >
> > > diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> > > index 864e43b008b1..ee4ac117aa3c 100644
> > > --- a/arch/x86/Kconfig
> > > +++ b/arch/x86/Kconfig
> > > @@ -1946,6 +1946,7 @@ config INTEL_TDX_HOST
> > >    	depends on KVM_INTEL
> > >    	depends on X86_X2APIC
> > >    	select ARCH_KEEP_MEMBLOCK
> > > +	depends on CONTIG_ALLOC
> > >    	help
> > >    	  Intel Trust Domain Extensions (TDX) protects guest VMs from malicious
> > >    	  host and certain physical attacks.  This option enables necessary TDX
> > > diff --git a/arch/x86/include/asm/shared/tdx.h b/arch/x86/include/asm/shared/tdx.h
> > > index abcca86b5af3..cb59fe329b00 100644
> > > --- a/arch/x86/include/asm/shared/tdx.h
> > > +++ b/arch/x86/include/asm/shared/tdx.h
> > > @@ -58,6 +58,7 @@
> > >    #define TDX_PS_4K	0
> > >    #define TDX_PS_2M	1
> > >    #define TDX_PS_1G	2
> > > +#define TDX_PS_NR	(TDX_PS_1G + 1)
> >
> > nit: I'd prefer if you those defines are turned into an enum and
> > subsequently this enum type can be used in the definition of
> > tdmr_get_pamt_sz(). However, at this point I consider this a
> > bikeshedding and you can do that iff you are going to respin the series
> > due to other feedback as well.
> >
> > <snip>
>
> Thanks for comments.  But to be honest I don't get why enum is better, and I
> would like to leave this to future work if really needed.  Please note these
> TDX_PS_xx are also used by TDX guest code (see patch 2).

The reason being self-documenting code. In particular when looking at 
the signature of tdmr_get_pamt_sz if the 2nd argument was enum 
tdx_ps_size or some such it would be immediately evident what this 
parameter is all about. Right now it's just a plain int which can be 
anything. Indeed, this is mostly cosmetic so hence it's minor.