From 9ec23a7f6d2537faf14368e066e307c06812c4ca Mon Sep 17 00:00:00 2001 From: Ian Campbell Date: Thu, 28 Oct 2010 11:32:29 -0700 Subject: [PATCH] xen: do not release any memory under 1M in domain 0 We already deliberately setup a 1-1 P2M for the region up to 1M in order to allow code which assumes this region is already mapped to work without having to convert everything to ioremap. Domain 0 should not return any apparently unused memory regions (reserved or otherwise) in this region to Xen since the e820 may not accurately reflect what the BIOS has stashed in this region. Signed-off-by: Ian Campbell Signed-off-by: Jeremy Fitzhardinge --- arch/x86/xen/setup.c | 18 +++++++++++------- 1 file changed, 11 insertions(+), 7 deletions(-) diff --git a/arch/x86/xen/setup.c b/arch/x86/xen/setup.c index b1dbdaa23ecc..769c4b01fa32 100644 --- a/arch/x86/xen/setup.c +++ b/arch/x86/xen/setup.c @@ -118,16 +118,18 @@ static unsigned long __init xen_return_unused_memory(unsigned long max_pfn, const struct e820map *e820) { phys_addr_t max_addr = PFN_PHYS(max_pfn); - phys_addr_t last_end = 0; + phys_addr_t last_end = ISA_END_ADDRESS; unsigned long released = 0; int i; + /* Free any unused memory above the low 1Mbyte. */ for (i = 0; i < e820->nr_map && last_end < max_addr; i++) { phys_addr_t end = e820->map[i].addr; end = min(max_addr, end); - released += xen_release_chunk(last_end, end); - last_end = e820->map[i].addr + e820->map[i].size; + if (last_end < end) + released += xen_release_chunk(last_end, end); + last_end = max(last_end, e820->map[i].addr + e820->map[i].size); } if (last_end < max_addr) @@ -164,6 +166,7 @@ char * __init xen_memory_setup(void) XENMEM_memory_map; rc = HYPERVISOR_memory_op(op, &memmap); if (rc == -ENOSYS) { + BUG_ON(xen_initial_domain()); memmap.nr_entries = 1; map[0].addr = 0ULL; map[0].size = mem_end; @@ -201,12 +204,13 @@ char * __init xen_memory_setup(void) } /* - * Even though this is normal, usable memory under Xen, reserve - * ISA memory anyway because too many things think they can poke + * In domU, the ISA region is normal, usable memory, but we + * reserve ISA memory anyway because too many things poke * about in there. * - * In a dom0 kernel, this region is identity mapped with the - * hardware ISA area, so it really is out of bounds. + * In Dom0, the host E820 information can leave gaps in the + * ISA range, which would cause us to release those pages. To + * avoid this, we unconditionally reserve them here. */ e820_add_region(ISA_START_ADDRESS, ISA_END_ADDRESS - ISA_START_ADDRESS, E820_RESERVED); -- GitLab