xen-devel
Re: [Xen-devel] 2.6.27-rc1 >4096MB issue
Jan Beulich wrote:
Jeremy Fitzhardinge <jeremy@xxxxxxxx> 05.08.08 05:07 >>>
Subject: make PFN_PHYS explicitly return 64-bit result
PFN_PHYS, as its name suggests, turns a pfn into a physical address.
However, it is a macro which just operates on its argument without
modifying its type. pfns are typed unsigned long, but an unsigned
long may not be long enough to hold a physical address (32-bit systems
with more than 32 bits of physcial address). This means that the
resulting address could be truncated if it doesn't fit within an
unsigned long. This isn't generally a problem because most users end
up using it for "low" memory, but there's no reason why PFN_PHYS
couldn't be used for any possible pfn.
Unfortunately there's no univerally recognized type for holding a full
physical address, so this patch makes it always return a u64 result.
Couldn't you use resource_size_t here?
Yeah, looks like I can. It had crossed my mind, but I'd vaguely
remembered that it might no be set if you don't have 64-bit IO devices.
But it looks like it's set for all interesting cases (64 bit machines,
and 32-bit x86 PAE).
J
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