Re: [PATCH 19/26] x86/tdx: Make pages shared in ioremap()

[Tom Lendacky]

On 1/4/22 6:43 PM, Dave Hansen wrote:
> On 1/4/22 4:31 PM, Kirill A. Shutemov wrote:
> > On Tue, Jan 04, 2022 at 12:36:06PM -0800, Dave Hansen wrote:
> > > @@ -57,7 +58,6 @@ typedef struct { unsigned long iopte; }
> > >   typedef struct { unsigned long pmd; } pmd_t;
> > >   typedef struct { unsigned long pgd; } pgd_t;
> > >   typedef struct { unsigned long ctxd; } ctxd_t;
> > > -typedef struct { unsigned long pgprot; } pgprot_t;
> > >   typedef struct { unsigned long iopgprot; } iopgprot_t;
> > >   
> > >   #define pte_val(x)	((x).pte)
> > > @@ -85,7 +85,6 @@ typedef unsigned long iopte_t;
> > >   typedef unsigned long pmd_t;
> > >   typedef unsigned long pgd_t;
> > >   typedef unsigned long ctxd_t;
> > > -typedef unsigned long pgprot_t;
> > >   typedef unsigned long iopgprot_t;
> > >   
> > >   #define pte_val(x)	(x)
> >
> > Any arch that use STRICT_MM_TYPECHECKS hacks will get broken if compiled
> > without the define (as sparc by default).
>
> My read of STRICT_MM_TYPECHECKS was that "typedef unsigned long
> pgprot_t" produces better code, but "typedef struct { unsigned long
> pgprot; } pgprot_t;" produces better type checking.
>
> I just compiled these patches on sparc with no issues.
>
> ...
> > Is it the way to go we want?
>
> I _think_ this was all a result of some review feedback from Tom
> Lendacky about where the encryption-modifying pgprot helpers got placed
> in the code.  I don't feel strongly about it, but I'm not quite sure
> that this is worth the trouble.
>
> I'd be curious what Tom thinks now that he's gotten a peek at what it's
> going to take to address his concerns.

I have vague memories of pgprot_t and what a pain it could be, which is 
why my feedback suggested putting it in cc_platform.c, but said there 
might be issues :)

I'm fine with it living somewhere else, just thought it would be nice to 
have everything consolidated, if possible.

Thanks,
Tom


>