From: Pavel Tatashin <pasha.tatashin@soleen.com>
To: Tyler Hicks <tyhicks@linux.microsoft.com>
Cc: James Morris <jmorris@namei.org>,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Anshuman Khandual <anshuman.khandual@arm.com>,
Mike Rapoport <rppt@kernel.org>,
Logan Gunthorpe <logang@deltatee.com>,
ardb@kernel.org, Linux ARM <linux-arm-kernel@lists.infradead.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] arm64: mm: correct the start of physical address in linear map
Date: Sat, 13 Feb 2021 13:17:11 -0500 [thread overview]
Message-ID: <CA+CK2bC4X4SmZ4FBXSBO15ErCd3yDeU9i97mZfQWbZaXN2AWNw@mail.gmail.com> (raw)
In-Reply-To: <20210213175151.GA4646@sequoia>
> We're ignoring the portion from the linear mapping's start PA to the
> point of wraparound. Could the start and end of the hot plugged memory
> fall within this range and, as a result, the hot plug operation be
> incorrectly blocked?
Hi Tyler,
Thank you for looking at this fix. The maximum addressable PA's can be
seen in this function: id_aa64mmfr0_parange_to_phys_shift(). For
example for PA shift 32, the linear map must be able to cover any
physical addresses from 0 to "1 << 32". Therefore, 0 to __pa(PAGE_END
- 1); must include 0 to "1<<32".
The randomization of the linear map tries to hide where exactly within
the linear map the [0 to max_phys] addresses are located by changing
PHYS_OFFSET (linear map space is usually much bigger than PA space).
Therefore, the beginning or end of a linear map can actually convert
to completely bagus high PA addresses, but this is normal.
Thank you,
Pasha
>
> Tyler
>
> > +
> > /*
> > * Linear mapping region is the range [PAGE_OFFSET..(PAGE_END - 1)]
> > * accommodating both its ends but excluding PAGE_END. Max physical
> > * range which can be mapped inside this linear mapping range, must
> > * also be derived from its end points.
> > */
> > - return start >= __pa(_PAGE_OFFSET(vabits_actual)) &&
> > - (start + size - 1) <= __pa(PAGE_END - 1);
> > + return start >= start_linear_pa && (start + size - 1) <= end_linear_pa;
> > }
> >
> > int arch_add_memory(int nid, u64 start, u64 size,
> > --
> > 2.25.1
> >
next prev parent reply other threads:[~2021-02-13 18:18 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-13 1:23 [PATCH] arm64: mm: correct the start of physical address in linear map Pavel Tatashin
2021-02-13 17:51 ` Tyler Hicks
2021-02-13 18:17 ` Pavel Tatashin [this message]
2021-02-15 5:26 ` Anshuman Khandual
2021-02-15 13:42 ` Pavel Tatashin
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