Date:   Wed, 5 Jan 2022 04:02:37 +0300
From:   "Kirill A. Shutemov" <kirill@shutemov.name>
To:     Dave Hansen <dave.hansen@intel.com>
Cc:     Borislav Petkov <bp@alien8.de>,
        "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
        Tom Lendacky <thomas.lendacky@amd.com>, tglx@linutronix.de,
        mingo@redhat.com, luto@kernel.org, peterz@infradead.org,
        sathyanarayanan.kuppuswamy@linux.intel.com, aarcange@redhat.com,
        ak@linux.intel.com, dan.j.williams@intel.com, david@redhat.com,
        hpa@zytor.com, jgross@suse.com, jmattson@google.com,
        joro@8bytes.org, jpoimboe@redhat.com, knsathya@kernel.org,
        pbonzini@redhat.com, sdeep@vmware.com, seanjc@google.com,
        tony.luck@intel.com, vkuznets@redhat.com, wanpengli@tencent.com,
        x86@kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 19/26] x86/tdx: Make pages shared in ioremap()
Message-ID: <20220105010237.ixyax4xi2anhga7t@box.shutemov.name>
References: <20220103141705.6hqflhwykqmtfim6@black.fi.intel.com>
 <YdMIWAT42el4D6wJ@zn.tnic>
 <20220103151516.pfcz2pap5l7r2rzv@box.shutemov.name>
 <b4b54116-1cd7-468a-0889-d497268cbfb2@intel.com>
 <20220103181059.ui5eloufw5gsojcb@box.shutemov.name>
 <20220104191424.oly2gqm4ltzj5wo3@box.shutemov.name>
 <0e0c38e2-67ad-1f51-c44b-d3c3d505e40a@intel.com>
 <20220105003108.mr7zyd5oyaaxmnmv@box.shutemov.name>
 <50dfa0db-fcd1-3c54-d982-237d2c9df431@intel.com>
 <20220105005720.zdtgwenqwqmuyxvi@box.shutemov.name>
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In-Reply-To: <20220105005720.zdtgwenqwqmuyxvi@box.shutemov.name>
Precedence: bulk

On Wed, Jan 05, 2022 at 03:57:20AM +0300, Kirill A. Shutemov wrote:
> On Tue, Jan 04, 2022 at 04:43:09PM -0800, 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.
> 
> Apart from pgprot_t, __pgprot() and pgrot_val() helpers are defined
> differently depending on STRICT_MM_TYPECHECKS.
> 
> > I just compiled these patches on sparc with no issues.
> 
> Hm. I can't see how
> 
> #define pgprot_val(x)	(x)
> 
> can work to access value for the pgprot_t defined as a struct.

Ah. I guess you compiled 64-bit sparc, right? STRICT_MM_TYPECHECKS is
default there, unline 32-bit.

-- 
 Kirill A. Shutemov