From: David Hildenbrand <david@redhat.com>
To: Gerald Schaefer <gerald.schaefer@linux.ibm.com>
Cc: linux-kernel@vger.kernel.org,
Andrew Morton <akpm@linux-foundation.org>,
Hugh Dickins <hughd@google.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
David Rientjes <rientjes@google.com>,
Shakeel Butt <shakeelb@google.com>,
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Jason Gunthorpe <jgg@nvidia.com>,
Mike Kravetz <mike.kravetz@oracle.com>,
Mike Rapoport <rppt@linux.ibm.com>,
Yang Shi <shy828301@gmail.com>,
"Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>,
Matthew Wilcox <willy@infradead.org>,
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Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
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linux-arm-kernel@lists.infradead.org,
linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org
Subject: Re: [PATCH v1 5/7] s390/pgtable: support __HAVE_ARCH_PTE_SWP_EXCLUSIVE
Date: Tue, 15 Mar 2022 18:14:04 +0100 [thread overview]
Message-ID: <51afa7a7-15c5-8769-78db-ed2d134792f4@redhat.com> (raw)
In-Reply-To: <55b6b582-51ca-b869-2055-674fe4c563e6@redhat.com>
On 15.03.22 18:12, David Hildenbrand wrote:
> On 15.03.22 17:58, David Hildenbrand wrote:
>>
>>>> This would mean that it is not OK to have bit 52 not zero for swap PTEs.
>>>> But if I read the POP correctly, all bits except for the DAT-protection
>>>> would be ignored for invalid PTEs, so maybe this comment needs some update
>>>> (for both bits 52 and also 55).
>>>>
>>>> Heiko might also have some more insight.
>>>
>>> Indeed, I wonder why we should get a specification exception when the
>>> PTE is invalid. I'll dig a bit into the PoP.
>>
>> SA22-7832-12 6-46 ("Translation-Specification Exception") is clearer
>>
>> "The page-table entry used for the translation is
>> valid, and bit position 52 does not contain zero."
>>
>> "The page-table entry used for the translation is
>> valid, EDAT-1 does not apply, the instruction-exe-
>> cution-protection facility is not installed, and bit
>> position 55 does not contain zero. It is model
>> dependent whether this condition is recognized."
>>
>
> I wonder if the following matches reality:
>
> diff --git a/arch/s390/include/asm/pgtable.h b/arch/s390/include/asm/pgtable.h
> index 008a6c856fa4..6a227a8c3712 100644
> --- a/arch/s390/include/asm/pgtable.h
> +++ b/arch/s390/include/asm/pgtable.h
> @@ -1669,18 +1669,16 @@ static inline int has_transparent_hugepage(void)
> /*
> * 64 bit swap entry format:
> * A page-table entry has some bits we have to treat in a special way.
> - * Bits 52 and bit 55 have to be zero, otherwise a specification
> - * exception will occur instead of a page translation exception. The
> - * specification exception has the bad habit not to store necessary
> - * information in the lowcore.
> * Bits 54 and 63 are used to indicate the page type.
> * A swap pte is indicated by bit pattern (pte & 0x201) == 0x200
> - * This leaves the bits 0-51 and bits 56-62 to store type and offset.
> - * We use the 5 bits from 57-61 for the type and the 52 bits from 0-51
> - * for the offset.
> - * | offset |01100|type |00|
> + * | offset |XX1XX|type |S0|
> * |0000000000111111111122222222223333333333444444444455|55555|55566|66|
> * |0123456789012345678901234567890123456789012345678901|23456|78901|23|
> + *
> + * Bits 0-51 store the offset.
> + * Bits 57-62 store the type.
^ 57-61, I should stop working for today :)
--
Thanks,
David / dhildenb
next prev parent reply other threads:[~2022-03-15 17:14 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-03-15 14:18 [PATCH v1 0/7] mm: COW fixes part 3: reliable GUP R/W FOLL_GET of anonymous pages David Hildenbrand
2022-03-15 14:18 ` [PATCH v1 1/7] mm/swap: remember PG_anon_exclusive via a swp pte bit David Hildenbrand
2022-03-15 14:18 ` [PATCH v1 2/7] mm/debug_vm_pgtable: add tests for __HAVE_ARCH_PTE_SWP_EXCLUSIVE David Hildenbrand
2022-03-15 14:18 ` [PATCH v1 3/7] x86/pgtable: support __HAVE_ARCH_PTE_SWP_EXCLUSIVE David Hildenbrand
2022-03-15 14:18 ` [PATCH v1 4/7] arm64/pgtable: " David Hildenbrand
2022-03-16 18:27 ` Catalin Marinas
2022-03-17 10:04 ` David Hildenbrand
2022-03-17 17:58 ` Catalin Marinas
2022-03-18 9:59 ` David Hildenbrand
2022-03-18 11:33 ` Catalin Marinas
2022-03-18 14:14 ` David Hildenbrand
2022-03-21 14:38 ` Will Deacon
2022-03-21 14:39 ` Will Deacon
2022-03-21 15:07 ` David Hildenbrand
2022-03-21 17:44 ` Will Deacon
2022-03-21 18:27 ` Catalin Marinas
2022-03-22 9:46 ` David Hildenbrand
2022-03-15 14:18 ` [PATCH v1 5/7] s390/pgtable: " David Hildenbrand
2022-03-15 16:21 ` Gerald Schaefer
2022-03-15 16:37 ` David Hildenbrand
2022-03-15 16:58 ` David Hildenbrand
2022-03-15 17:12 ` David Hildenbrand
2022-03-15 17:14 ` David Hildenbrand [this message]
2022-03-16 10:56 ` Gerald Schaefer
2022-03-16 11:06 ` David Hildenbrand
2022-03-16 13:01 ` Christian Borntraeger
2022-03-16 13:27 ` Gerald Schaefer
2022-03-16 14:00 ` David Hildenbrand
2022-03-15 14:18 ` [PATCH v1 6/7] powerpc/pgtable: remove _PAGE_BIT_SWAP_TYPE for book3s David Hildenbrand
2022-03-15 14:18 ` [PATCH v1 7/7] powerpc/pgtable: support __HAVE_ARCH_PTE_SWP_EXCLUSIVE " David Hildenbrand
2022-03-18 23:48 ` [PATCH v1 0/7] mm: COW fixes part 3: reliable GUP R/W FOLL_GET of anonymous pages Jason Gunthorpe
2022-03-19 11:17 ` David Hildenbrand
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