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xen/e820: Don't mark balloon memory as E820_UNUSABLE when running as guest and fix overflow.
If we have a guest that asked for: memory=1024 maxmem=2048 Which means we want 1GB now, and create pagetables so that we can expand up to 2GB, we would have this E820 layout: [ 0.000000] BIOS-provided physical RAM map: [ 0.000000] Xen: 0000000000000000 - 00000000000a0000 (usable) [ 0.000000] Xen: 00000000000a0000 - 0000000000100000 (reserved) [ 0.000000] Xen: 0000000000100000 - 0000000080800000 (usable) Due to patch: "xen/setup: Inhibit resource API from using System RAM E820 gaps as PCI mem gaps." we would mark the memory past the 1GB mark as unusuable resulting in: [ 0.000000] BIOS-provided physical RAM map: [ 0.000000] Xen: 0000000000000000 - 00000000000a0000 (usable) [ 0.000000] Xen: 00000000000a0000 - 0000000000100000 (reserved) [ 0.000000] Xen: 0000000000100000 - 0000000040000000 (usable) [ 0.000000] Xen: 0000000040000000 - 0000000080800000 (unusable) which meant that we could not balloon up anymore. We could balloon the guest down. The fix is to run the code introduced by the above mentioned patch only for the initial domain. We will have to revisit this once we start introducing a modified E820 for PCI passthrough so that we can utilize the P2M identity code. We also fix an overflow by having UL instead of ULL on 32-bit machines. [v2: Ian pointed to the overflow issue] Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
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@ -200,7 +200,8 @@ char * __init xen_memory_setup(void)
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* used as potential resource for I/O address (happens
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* when 'allocate_resource' is called).
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*/
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if (delta && end < 0x100000000UL)
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if (delta &&
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(xen_initial_domain() && end < 0x100000000ULL))
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e820_add_region(end, delta, E820_UNUSABLE);
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}
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