linux-kernel - Re: [PATCH] x86/mm: Fix PAGE_KERNEL

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Message-ID: <35ba181f-c182-aa74-07e2-fcff94bf345a@amd.com>
Date:   Fri, 3 Dec 2021 11:28:58 -0600
From:   Tom Lendacky <thomas.lendacky@....com>
To:     Lucas De Marchi <lucas.demarchi@...el.com>,
        Joerg Roedel <joro@...tes.org>
Cc:     x86@...nel.org, Dave Hansen <dave.hansen@...ux.intel.com>,
        Borislav Petkov <bp@...en8.de>, Ingo Molnar <mingo@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>, hpa@...or.com,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Brijesh Singh <brijesh.singh@....com>,
        linux-kernel@...r.kernel.org, Joerg Roedel <jroedel@...e.de>
Subject: Re: [PATCH] x86/mm: Fix PAGE_KERNEL_IO removal breakage

On 12/2/21 6:25 PM, Lucas De Marchi wrote:
> On Thu, Dec 02, 2021 at 07:55:14AM -0800, Lucas De Marchi wrote:
>> On Thu, Dec 02, 2021 at 03:46:46PM +0100, Joerg Roedel wrote:
>>> From: Joerg Roedel <jroedel@...e.de>
>>>
>>> The removal of PAGE_KERNEL_IO broke SEV-ES because it changed the
>>> mapping of ioremap and some fixmap areas (like the local APIC page)
>>> from unencrypted to encrypted. Change those mappings back to
>>> be unencrypted.
>>>
>>> Cc: Lucas De Marchi <lucas.demarchi@...el.com>
>>> Fixes: 27dff0f58bde ("x86/mm: Nuke PAGE_KERNEL_IO")
>>> Signed-off-by: Joerg Roedel <jroedel@...e.de>
>>
>> oops, missed the fact PAGE_KERNEL had `| ENC` while PAGE_KERENL_IO
>> didn't have it. Thanks for the fixup.
> 
> on a second thought, the fact that PAGE_KERNEL is _not_ the same as
> PAGE_KERNEL_IO, completely invalidates those 2 patches I sent. It seems
> I screwed it up big here.
> 
> About the first patch,
> 6b2a2138cf36 ("drm/i915/gem: Stop using PAGE_KERNEL_IO"),
> I didn't notice any regression on the i915
> side though. Is it safe to keep it? Otherwise we are probably better
> off reverting everything.
> 
> I'm wondering why the addition of memory encryption
> in 21729f81ce8a ("x86/mm: Provide general kernel support for memory 
> encryption")
> didn't break io_mapping_init_wc() though as it had already done a
> s/PAGE_KERNEL_IO/PAGE_KERNEL/ in commit
> ac96b5566926 ("io-mapping.h: s/PAGE_KERNEL_IO/PAGE_KERNEL/")

If I follow it correctly, since SME/SEV-ES are X86_64 only, 
io_mapping_init_wc() takes the ioremap_wc() path which uses 
PAGE_KERNEL_IO. iomap_create_wc() is only called when 
CONFIG_HAVE_ATOMIC_IOMAP is set, which isn't set for X86_64.

Thanks,
Tom

> 
> thanks
> Lucas De Marchi
> 
>>
>> Reviewed-by: Lucas De Marchi <lucas.demarchi@...el.com>
>>
>> Lucas De Marchi
>>
>>> ---
>>> arch/x86/include/asm/fixmap.h        |  2 +-
>>> arch/x86/include/asm/pgtable_types.h | 21 +++++++++++----------
>>> arch/x86/mm/ioremap.c                |  2 +-
>>> 3 files changed, 13 insertions(+), 12 deletions(-)
>>>
>>> diff --git a/arch/x86/include/asm/fixmap.h b/arch/x86/include/asm/fixmap.h
>>> index 5e186a69db10..a2eaf265f784 100644
>>> --- a/arch/x86/include/asm/fixmap.h
>>> +++ b/arch/x86/include/asm/fixmap.h
>>> @@ -173,7 +173,7 @@ static inline void __set_fixmap(enum 
>>> fixed_addresses idx,
>>> * supported for MMIO addresses, so make sure that the memory encryption
>>> * mask is not part of the page attributes.
>>> */
>>> -#define FIXMAP_PAGE_NOCACHE PAGE_KERNEL_NOCACHE
>>> +#define FIXMAP_PAGE_NOCACHE PAGE_KERNEL_NOCACHE_NOENC
>>>
>>> /*
>>> * Early memremap routines used for in-place encryption. The mappings 
>>> created
>>> diff --git a/arch/x86/include/asm/pgtable_types.h 
>>> b/arch/x86/include/asm/pgtable_types.h
>>> index a87224767ff3..fc9b6995cb22 100644
>>> --- a/arch/x86/include/asm/pgtable_types.h
>>> +++ b/arch/x86/include/asm/pgtable_types.h
>>> @@ -208,16 +208,17 @@ enum page_cache_mode {
>>>
>>> #define __pgprot_mask(x)    __pgprot((x) & __default_kernel_pte_mask)
>>>
>>> -#define PAGE_KERNEL        __pgprot_mask(__PAGE_KERNEL            | _ENC)
>>> -#define PAGE_KERNEL_NOENC    __pgprot_mask(__PAGE_KERNEL            
>>> |    0)
>>> -#define PAGE_KERNEL_RO        __pgprot_mask(__PAGE_KERNEL_RO         | 
>>> _ENC)
>>> -#define PAGE_KERNEL_EXEC    __pgprot_mask(__PAGE_KERNEL_EXEC       | 
>>> _ENC)
>>> -#define PAGE_KERNEL_EXEC_NOENC    
>>> __pgprot_mask(__PAGE_KERNEL_EXEC       |    0)
>>> -#define PAGE_KERNEL_ROX        __pgprot_mask(__PAGE_KERNEL_ROX        
>>> | _ENC)
>>> -#define PAGE_KERNEL_NOCACHE    __pgprot_mask(__PAGE_KERNEL_NOCACHE    
>>> | _ENC)
>>> -#define PAGE_KERNEL_LARGE    __pgprot_mask(__PAGE_KERNEL_LARGE      | 
>>> _ENC)
>>> -#define PAGE_KERNEL_LARGE_EXEC    
>>> __pgprot_mask(__PAGE_KERNEL_LARGE_EXEC | _ENC)
>>> -#define PAGE_KERNEL_VVAR    __pgprot_mask(__PAGE_KERNEL_VVAR       | 
>>> _ENC)
>>> +#define PAGE_KERNEL            __pgprot_mask(__PAGE_KERNEL            
>>> | _ENC)
>>> +#define PAGE_KERNEL_NOENC        
>>> __pgprot_mask(__PAGE_KERNEL            |    0)
>>> +#define PAGE_KERNEL_RO            
>>> __pgprot_mask(__PAGE_KERNEL_RO         | _ENC)
>>> +#define PAGE_KERNEL_EXEC        __pgprot_mask(__PAGE_KERNEL_EXEC       
>>> | _ENC)
>>> +#define PAGE_KERNEL_EXEC_NOENC        
>>> __pgprot_mask(__PAGE_KERNEL_EXEC       |    0)
>>> +#define PAGE_KERNEL_ROX            
>>> __pgprot_mask(__PAGE_KERNEL_ROX        | _ENC)
>>> +#define PAGE_KERNEL_NOCACHE        
>>> __pgprot_mask(__PAGE_KERNEL_NOCACHE    | _ENC)
>>> +#define PAGE_KERNEL_NOCACHE_NOENC    
>>> __pgprot_mask(__PAGE_KERNEL_NOCACHE    |    0)
>>> +#define PAGE_KERNEL_LARGE        
>>> __pgprot_mask(__PAGE_KERNEL_LARGE      | _ENC)
>>> +#define PAGE_KERNEL_LARGE_EXEC        
>>> __pgprot_mask(__PAGE_KERNEL_LARGE_EXEC | _ENC)
>>> +#define PAGE_KERNEL_VVAR        __pgprot_mask(__PAGE_KERNEL_VVAR       
>>> | _ENC)
>>>
>>> #endif    /* __ASSEMBLY__ */
>>>
>>> diff --git a/arch/x86/mm/ioremap.c b/arch/x86/mm/ioremap.c
>>> index 3102dda4b152..4fe8d43d53bb 100644
>>> --- a/arch/x86/mm/ioremap.c
>>> +++ b/arch/x86/mm/ioremap.c
>>> @@ -243,7 +243,7 @@ __ioremap_caller(resource_size_t phys_addr, 
>>> unsigned long size,
>>>      * make sure the memory encryption attribute is enabled in the
>>>      * resulting mapping.
>>>      */
>>> -    prot = PAGE_KERNEL;
>>> +    prot = PAGE_KERNEL_NOENC;
>>>     if ((io_desc.flags & IORES_MAP_ENCRYPTED) || encrypted)
>>>         prot = pgprot_encrypted(prot);
>>>
>>> -- 
>>> 2.34.0
>>>