From: David Hildenbrand <david@redhat.com>
To: Anshuman Khandual <anshuman.khandual@arm.com>,
linux-mm@kvack.org, akpm@linux-foundation.org, hca@linux.ibm.com,
catalin.marinas@arm.com
Cc: Oscar Salvador <osalvador@suse.de>,
Vasily Gorbik <gor@linux.ibm.com>, Will Deacon <will@kernel.org>,
Ard Biesheuvel <ardb@kernel.org>,
Mark Rutland <mark.rutland@arm.com>,
linux-arm-kernel@lists.infradead.org, linux-s390@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH V3 1/3] mm/memory_hotplug: Prevalidate the address range being added with platform
Date: Fri, 22 Jan 2021 10:18:21 +0100 [thread overview]
Message-ID: <9916f217-ec29-33ff-a260-7a26792d23a1@redhat.com> (raw)
In-Reply-To: <1610975582-12646-2-git-send-email-anshuman.khandual@arm.com>
> +/*
> + * Platforms should define arch_get_mappable_range() that provides
> + * maximum possible addressable physical memory range for which the
> + * linear mapping could be created. The platform returned address
> + * range must adhere to these following semantics.
> + *
> + * - range.start <= range.end
> + * - Range includes both end points [range.start..range.end]
> + *
> + * There is also a fallback definition provided here, allowing the
> + * entire possible physical address range in case any platform does
> + * not define arch_get_mappable_range().
> + */
> +struct range __weak arch_get_mappable_range(void)
> +{
> + struct range memhp_range = {
> + .start = 0UL,
> + .end = -1ULL,
> + };
> + return memhp_range;
> +}
> +
> +struct range memhp_get_pluggable_range(bool need_mapping)
> +{
> + const u64 max_phys = (1ULL << (MAX_PHYSMEM_BITS + 1)) - 1;
Sorry, thought about that line a bit more, and I think this is just
wrong (took me longer to realize as it should). The old code used this
calculation to print the limit only (in a wrong way), let's recap:
Assume MAX_PHYSMEM_BITS=32
max_phys = (1ULL << (32 + 1)) - 1 = 0x1ffffffffull;
Ehm, these are 33 bit.
OTOH, old code checked for
if (max_addr >> MAX_PHYSMEM_BITS) {
Which makes sense, because
0x1ffffffffull >> 32 = 1
results in "true", meaning it's to big, while
0xffffffffull >> 32 = 0
correctly results in "false", meaning the address is fine.
So, this should just be
const u64 max_phys = 1ULL << MAX_PHYSMEM_BITS;
(similarly as calculated in virito-mem code, or in kernel/resource.c)
> + struct range memhp_range;
> +
> + if (need_mapping) {
> + memhp_range = arch_get_mappable_range();
> + if (memhp_range.start > max_phys) {
> + memhp_range.start = 0;
> + memhp_range.end = 0;
> + }
> + memhp_range.end = min_t(u64, memhp_range.end, max_phys);
> + } else {
> + memhp_range.start = 0;
> + memhp_range.end = max_phys;
> + }
> + return memhp_range;
> +}
> +EXPORT_SYMBOL_GPL(memhp_get_pluggable_range);
--
Thanks,
David / dhildenb
next prev parent reply other threads:[~2021-01-22 9:18 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-18 13:12 [PATCH V3 0/3] mm/memory_hotplug: Pre-validate the address range with platform Anshuman Khandual
2021-01-18 13:12 ` [PATCH V3 1/3] mm/memory_hotplug: Prevalidate the address range being added " Anshuman Khandual
2021-01-19 12:21 ` David Hildenbrand
2021-01-20 8:33 ` Anshuman Khandual
2021-01-20 10:41 ` David Hildenbrand
2021-01-20 11:58 ` Oscar Salvador
2021-01-21 9:23 ` Oscar Salvador
2021-01-22 9:18 ` David Hildenbrand [this message]
2021-01-22 10:41 ` Anshuman Khandual
2021-01-22 10:42 ` David Hildenbrand
2021-01-22 10:43 ` David Hildenbrand
2021-01-18 13:13 ` [PATCH V3 2/3] arm64/mm: Define arch_get_mappable_range() Anshuman Khandual
2021-01-19 12:24 ` David Hildenbrand
2021-01-18 13:13 ` [PATCH V3 3/3] s390/mm: " Anshuman Khandual
2021-01-19 12:26 ` David Hildenbrand
2021-01-20 8:28 ` Anshuman Khandual
2021-01-20 10:39 ` David Hildenbrand
2021-01-18 13:13 ` [PATCH RFC] virtio-mem: check against memhp_get_pluggable_range() which memory we can hotplug Anshuman Khandual
2021-01-18 13:21 ` Anshuman Khandual
2021-01-19 12:27 ` David Hildenbrand
2021-01-21 9:57 ` David Hildenbrand
2021-01-22 3:32 ` Anshuman Khandual
2021-01-19 13:33 ` [PATCH V3 0/3] mm/memory_hotplug: Pre-validate the address range with platform David Hildenbrand
2021-01-19 13:40 ` Oscar Salvador
2021-01-20 8:37 ` Anshuman Khandual
2021-01-22 6:04 ` Anshuman Khandual
2021-01-22 8:34 ` David Hildenbrand
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