Handle overflow in calculating max kmem size.
vm_kmem_size is u_long, and it might be not capable of holding page count times PAGE_SIZE, even when scaled down by VM_KMEM_SIZE_SCALE. As bde reported, 12G PAE config ends up with zero for kmem size. Explicitly check for overflow and clamp kmem size at vm_kmem_size_max. If we end up at zero size because VM_KMEM_SIZE_MAX is not defined, panic with clear explanation rather then failing in a way which is hard to relate. Reported by: bde, pho Tested by: pho Reviewed by: markj Sponsored by: The FreeBSD Foundation MFC after: 1 week Differential revision: https://reviews.freebsd.org/D18767
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2020-12-20 02:59:44 +00:00
svn path=/head/; revision=343017
@ -920,13 +920,16 @@ kmeminit(void)
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* variable:
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*/
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if (vm_kmem_size == 0) {
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vm_kmem_size = (mem_size / vm_kmem_size_scale) * PAGE_SIZE;
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vm_kmem_size = mem_size / vm_kmem_size_scale;
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vm_kmem_size = vm_kmem_size * PAGE_SIZE < vm_kmem_size ?
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vm_kmem_size_max : vm_kmem_size * PAGE_SIZE;
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if (vm_kmem_size_min > 0 && vm_kmem_size < vm_kmem_size_min)
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vm_kmem_size = vm_kmem_size_min;
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if (vm_kmem_size_max > 0 && vm_kmem_size >= vm_kmem_size_max)
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vm_kmem_size = vm_kmem_size_max;
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}
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if (vm_kmem_size == 0)
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panic("Tune VM_KMEM_SIZE_* for the platform");
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/*
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* The amount of KVA space that is preallocated to the
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