From: Linus Torvalds <torvalds@linux-foundation.org>
To: Borislav Petkov <bp@alien8.de>
Cc: "Luis R. Rodriguez" <mcgrof@suse.com>,
Toshi Kani <toshi.kani@hp.com>,
Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@kernel.org>, Peter Anvin <hpa@zytor.com>,
Denys Vlasenko <dvlasenk@redhat.com>,
Borislav Petkov <bp@suse.de>,
Andrew Morton <akpm@linux-foundation.org>,
Brian Gerst <brgerst@gmail.com>,
Thomas Gleixner <tglx@linutronix.de>,
linux-mm <linux-mm@kvack.org>,
Andy Lutomirski <luto@amacapital.net>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
"linux-tip-commits@vger.kernel.org"
<linux-tip-commits@vger.kernel.org>
Subject: Re: [tip:x86/mm] x86/mm/mtrr: Clean up mtrr_type_lookup()
Date: Sat, 1 Aug 2015 09:39:07 -0700 [thread overview]
Message-ID: <CA+55aFzBvRYLufS46QR2aXLYX=rMBQ-qKjkkhQm-L9dFgwWywA@mail.gmail.com> (raw)
In-Reply-To: <20150801163311.GA15356@nazgul.tnic>
On Sat, Aug 1, 2015 at 9:33 AM, Borislav Petkov <bp@alien8.de> wrote:
>
> Well, it doesn't really make sense to write-combine IO memory, does it?
Quite the reverse.
It makes no sense to write-combine normal memory (RAM), because caches
work and sane memory is always cache-coherent. So marking regular
memory write-combining is a sign of crap hardware (which admittedly
exists all too much, but hopefully goes away).
In contrast, marking MMIO memory write-combining is not a sign of crap
hardware - it's just a sign of things like frame buffers on the card
etc. Which very much wants write combining. So WC for MMIO at least
makes sense.
Yes, yes, I realize that "crap hardware" may actually be the more
common case, but still..
Linus
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next prev parent reply other threads:[~2015-08-01 16:39 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-05-15 18:23 [PATCH v5 0/6] mtrr, mm, x86: Enhance MTRR checks for huge I/O mapping Toshi Kani
2015-05-15 18:23 ` [PATCH v5 1/6] mm, x86: Simplify conditions of HAVE_ARCH_HUGE_VMAP Toshi Kani
2015-05-17 8:30 ` Borislav Petkov
[not found] ` <1432628901-18044-2-git-send-email-bp@alien8.de>
2015-05-27 14:17 ` [tip:x86/mm] x86/mm/kconfig: Simplify conditions for HAVE_ARCH_HUGE_VMAP tip-bot for Toshi Kani
2015-05-15 18:23 ` [PATCH v5 2/6] mtrr, x86: Fix MTRR lookup to handle inclusive entry Toshi Kani
[not found] ` <1432628901-18044-3-git-send-email-bp@alien8.de>
2015-05-27 14:18 ` [tip:x86/mm] x86/mm/mtrr: Fix MTRR lookup to handle an " tip-bot for Toshi Kani
2015-05-15 18:23 ` [PATCH v5 3/6] mtrr, x86: Fix MTRR state checks in mtrr_type_lookup() Toshi Kani
[not found] ` <1432628901-18044-4-git-send-email-bp@alien8.de>
2015-05-27 14:18 ` [tip:x86/mm] x86/mm/mtrr: " tip-bot for Toshi Kani
2015-05-15 18:23 ` [PATCH v5 4/6] mtrr, x86: Define MTRR_TYPE_INVALID for mtrr_type_lookup() Toshi Kani
[not found] ` <1432628901-18044-5-git-send-email-bp@alien8.de>
2015-05-27 14:18 ` [tip:x86/mm] x86/mm/mtrr: Use symbolic define as a retval for disabled MTRRs tip-bot for Toshi Kani
2015-05-15 18:23 ` [PATCH v5 5/6] mtrr, x86: Clean up mtrr_type_lookup() Toshi Kani
[not found] ` <1432628901-18044-6-git-send-email-bp@alien8.de>
2015-05-27 14:19 ` [tip:x86/mm] x86/mm/mtrr: " tip-bot for Toshi Kani
2015-07-31 13:18 ` Peter Zijlstra
2015-07-31 14:44 ` Borislav Petkov
2015-07-31 15:08 ` Peter Zijlstra
2015-07-31 15:27 ` Borislav Petkov
2015-08-01 14:28 ` Luis R. Rodriguez
2015-08-01 16:33 ` Borislav Petkov
2015-08-01 16:39 ` Linus Torvalds [this message]
2015-08-01 16:49 ` Borislav Petkov
2015-08-01 17:03 ` Linus Torvalds
2015-05-15 18:23 ` [PATCH v5 6/6] mtrr, mm, x86: Enhance MTRR checks for KVA huge page mapping Toshi Kani
2015-05-18 13:33 ` Borislav Petkov
2015-05-18 17:22 ` Toshi Kani
2015-05-18 19:01 ` Borislav Petkov
2015-05-18 19:31 ` Toshi Kani
2015-05-18 20:01 ` Borislav Petkov
2015-05-18 20:21 ` Toshi Kani
2015-05-18 20:51 ` Borislav Petkov
2015-05-18 21:53 ` Toshi Kani
2015-05-19 11:44 ` Borislav Petkov
2015-05-19 13:23 ` Borislav Petkov
2015-05-19 13:47 ` Toshi Kani
2015-05-20 11:55 ` Ingo Molnar
2015-05-20 14:34 ` Toshi Kani
2015-05-20 15:01 ` Ingo Molnar
2015-05-20 15:02 ` Toshi Kani
2015-05-20 16:04 ` Borislav Petkov
2015-05-20 15:46 ` Toshi Kani
[not found] ` <1432628901-18044-8-git-send-email-bp@alien8.de>
2015-05-27 14:19 ` [tip:x86/mm] x86/mm/mtrr: Enhance MTRR checks in kernel mapping helpers tip-bot for Toshi Kani
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