From: Ankur Arora <ankur.a.arora@oracle.com>
To: Andy Lutomirski <luto@kernel.org>
Cc: LKML <linux-kernel@vger.kernel.org>,
Linux-MM <linux-mm@kvack.org>,
"Kirill A. Shutemov" <kirill@shutemov.name>,
Michal Hocko <mhocko@kernel.org>,
Boris Ostrovsky <boris.ostrovsky@oracle.com>,
Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
X86 ML <x86@kernel.org>, "H. Peter Anvin" <hpa@zytor.com>,
Arnd Bergmann <arnd@arndb.de>,
Andrew Morton <akpm@linux-foundation.org>,
Ira Weiny <ira.weiny@intel.com>,
linux-arch <linux-arch@vger.kernel.org>
Subject: Re: [PATCH 5/8] x86/clear_page: add clear_page_uncached()
Date: Wed, 14 Oct 2020 13:54:00 -0700 [thread overview]
Message-ID: <047e8a34-65cb-ce46-bfe2-014a43b61560@oracle.com> (raw)
In-Reply-To: <CALCETrVKLv5DPByFcj7E5SBbv4mFt7mGQ9j-HU7G5u_aPGCYsQ@mail.gmail.com>
On 2020-10-14 8:45 a.m., Andy Lutomirski wrote:
> On Wed, Oct 14, 2020 at 1:33 AM Ankur Arora <ankur.a.arora@oracle.com> wrote:
>>
>> Define clear_page_uncached() as an alternative_call() to clear_page_nt()
>> if the CPU sets X86_FEATURE_NT_GOOD and fallback to clear_page() if it
>> doesn't.
>>
>> Similarly define clear_page_uncached_flush() which provides an SFENCE
>> if the CPU sets X86_FEATURE_NT_GOOD.
>
> As long as you keep "NT" or "MOVNTI" in the names and keep functions
> in arch/x86, I think it's reasonable to expect that callers understand
> that MOVNTI has bizarre memory ordering rules. But once you give
> something a generic name like "clear_page_uncached" and stick it in
> generic code, I think the semantics should be more obvious.
>
> How about:
>
> clear_page_uncached_unordered() or clear_page_uncached_incoherent()
>
> and
>
> flush_after_clear_page_uncached()
>
> After all, a naive reader might expect "uncached" to imply "caches are
> off and this is coherent with everything". And the results of getting
> this wrong will be subtle and possibly hard-to-reproduce corruption.
Yeah, these are a lot more obvious. Thanks. Will fix.
Ankur
>
> --Andy
>
next prev parent reply other threads:[~2020-10-14 20:56 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-14 8:32 [PATCH 0/8] Use uncached writes while clearing gigantic pages Ankur Arora
2020-10-14 8:32 ` [PATCH 1/8] x86/cpuid: add X86_FEATURE_NT_GOOD Ankur Arora
2020-10-14 8:32 ` [PATCH 2/8] x86/asm: add memset_movnti() Ankur Arora
2020-10-14 8:32 ` [PATCH 3/8] perf bench: " Ankur Arora
2020-10-14 8:32 ` [PATCH 4/8] x86/asm: add clear_page_nt() Ankur Arora
2020-10-14 19:56 ` Borislav Petkov
2020-10-14 21:11 ` Ankur Arora
2020-10-14 8:32 ` [PATCH 5/8] x86/clear_page: add clear_page_uncached() Ankur Arora
2020-10-14 11:10 ` kernel test robot
2020-10-14 11:10 ` kernel test robot
2020-10-14 13:04 ` kernel test robot
2020-10-14 13:04 ` kernel test robot
2020-10-14 15:45 ` Andy Lutomirski
2020-10-14 15:45 ` Andy Lutomirski
2020-10-14 19:58 ` Borislav Petkov
2020-10-14 21:07 ` Andy Lutomirski
2020-10-14 21:12 ` Borislav Petkov
2020-10-15 3:37 ` Ankur Arora
2020-10-15 10:35 ` Borislav Petkov
2020-10-15 21:20 ` Ankur Arora
2020-10-16 18:21 ` Borislav Petkov
2020-10-15 3:21 ` Ankur Arora
2020-10-15 10:40 ` Borislav Petkov
2020-10-15 21:40 ` Ankur Arora
2020-10-14 20:54 ` Ankur Arora [this message]
2020-10-14 8:32 ` [PATCH 6/8] mm, clear_huge_page: use clear_page_uncached() for gigantic pages Ankur Arora
2020-10-14 15:28 ` Ingo Molnar
2020-10-14 19:15 ` Ankur Arora
2020-10-14 8:32 ` [PATCH 7/8] x86/cpu/intel: enable X86_FEATURE_NT_GOOD on Intel Broadwellx Ankur Arora
2020-10-14 15:31 ` Ingo Molnar
2020-10-14 19:23 ` Ankur Arora
2020-10-14 8:32 ` [PATCH 8/8] x86/cpu/amd: enable X86_FEATURE_NT_GOOD on AMD Zen Ankur Arora
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