Re: [PATCH] x86/mm: Fix PAGE_KERNEL_IO removal breakage

[Tom Lendacky <thomas.lendacky@amd.com>]

On 12/3/21 11:28 AM, Tom Lendacky wrote:
> 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@suse.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@intel.com>
>>>> Fixes: 27dff0f58bde ("x86/mm: Nuke PAGE_KERNEL_IO")
>>>> Signed-off-by: Joerg Roedel <jroedel@suse.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.

Is i915 for just integrated graphics? In which case SME/SEV-ES aren't 
available on Intel.

Thanks,
Tom

>>
>> 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@intel.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
>>>>