From: Toshi Kani <toshi.kani@hp.com>
To: Ingo Molnar <mingo@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>,
akpm@linux-foundation.org, hpa@zytor.com, tglx@linutronix.de,
mingo@redhat.com, linux-mm@kvack.org, x86@kernel.org,
linux-kernel@vger.kernel.org, dave.hansen@intel.com,
Elliott@hp.com, pebolle@tiscali.nl, mcgrof@suse.com
Subject: Re: [PATCH v5 6/6] mtrr, mm, x86: Enhance MTRR checks for KVA huge page mapping
Date: Wed, 20 May 2015 08:34:11 -0600 [thread overview]
Message-ID: <1432132451.700.4.camel@misato.fc.hp.com> (raw)
In-Reply-To: <20150520115509.GA3489@gmail.com>
On Wed, 2015-05-20 at 13:55 +0200, Ingo Molnar wrote:
> * Borislav Petkov <bp@alien8.de> wrote:
>
> > --- a/arch/x86/mm/pgtable.c
> > +++ b/arch/x86/mm/pgtable.c
> > @@ -566,19 +566,28 @@ void native_set_fixmap(enum fixed_addresses idx, phys_addr_t phys,
> > /**
> > * pud_set_huge - setup kernel PUD mapping
> > *
> > - * MTRR can override PAT memory types with 4KiB granularity. Therefore,
> > - * this function does not set up a huge page when the range is covered
> > - * by a non-WB type of MTRR. MTRR_TYPE_INVALID indicates that MTRR are
> > - * disabled.
> > + * MTRRs can override PAT memory types with 4KiB granularity. Therefore, this
> > + * function sets up a huge page only if any of the following conditions are met:
> > + *
> > + * - MTRRs are disabled, or
> > + *
> > + * - MTRRs are enabled and the range is completely covered by a single MTRR, or
> > + *
> > + * - MTRRs are enabled and the range is not completely covered by a single MTRR
> > + * but the memory type of the range is WB, even if covered by multiple MTRRs.
> > + *
> > + * Callers should try to decrease page size (1GB -> 2MB -> 4K) if the bigger
> > + * page mapping attempt fails.
>
> This comment should explain why it's ok in the WB case.
>
> Also, the phrase 'the memory type of the range' is ambiguous: it might
> mean the partial MTRR's, or the memory type specified via PAT by the
> huge-pmd entry.
Agreed. How about this sentence?
- MTRRs are enabled and the corresponding MTRR memory type is WB, which
has no effect to the requested PAT memory type.
Thanks,
-Toshi
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next prev parent reply other threads:[~2015-05-20 14:53 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
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 [this message]
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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