Add a config option to set the max size of a Xen domain. This is used to scale the size of the physical-to-machine array; it ends up using around 1 page/GByte, so there's no reason to be very restrictive.

For a 32-bit guest, the default value of 8GB is probably sufficient; there's not much point in giving a 32-bit machine much more memory than that.

Signed-off-by: Jeremy Fitzhardinge <jere...@citrix.com>

--- arch/x86/xen/Kconfig | 10 ++++++++++ arch/x86/xen/mmu.c | 25 ++++++++++++------------- arch/x86/xen/setup.c | 3 +++ include/asm-x86/xen/page.h | 5 +++++ 4 files changed, 30 insertions(+), 13 deletions(-)

diff --git a/arch/x86/xen/Kconfig b/arch/x86/xen/Kconfig --- a/arch/x86/xen/Kconfig +++ b/arch/x86/xen/Kconfig @@ -11,3 +11,13 @@ This is the Linux Xen port. Enabling this will allow the kernel to boot in a paravirtualized environment under the Xen hypervisor. + +config XEN_MAX_DOMAIN_MEMORY + int "Maximum allowed size of a domain in gigabytes" + default 8 + depends on XEN + help + The pseudo-physical to machine address array is sized + according to the maximum possible memory size of a Xen + domain. This array uses 1 page per gigabyte, so there's no + need to be too stingy here. \ No newline at end of file diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c --- a/arch/x86/xen/mmu.c +++ b/arch/x86/xen/mmu.c @@ -56,19 +56,13 @@ #include "multicalls.h" #include "mmu.h"

-/* - * This should probably be a config option. On 32-bit, it costs 1 - * page/gig of memory; on 64-bit its 2 pages/gig. If we want it to be - * completely unbounded we can add another level to the p2m structure. - */ -#define MAX_GUEST_PAGES (16ull * 1024*1024*1024 / PAGE_SIZE) #define P2M_ENTRIES_PER_PAGE (PAGE_SIZE / sizeof(unsigned long))

-static unsigned long *p2m_top[MAX_GUEST_PAGES / P2M_ENTRIES_PER_PAGE]; +static unsigned long *p2m_top[MAX_DOMAIN_PAGES / P2M_ENTRIES_PER_PAGE];

static inline unsigned p2m_top_index(unsigned long pfn) { - BUG_ON(pfn >= MAX_GUEST_PAGES); + BUG_ON(pfn >= MAX_DOMAIN_PAGES); return pfn / P2M_ENTRIES_PER_PAGE; }

@@ -81,12 +75,9 @@ { unsigned pfn; unsigned long *mfn_list = (unsigned long *)xen_start_info->mfn_list; + unsigned long max_pfn = min(MAX_DOMAIN_PAGES, xen_start_info->nr_pages);

- BUG_ON(xen_start_info->nr_pages >= MAX_GUEST_PAGES); - - for(pfn = 0; - pfn < xen_start_info->nr_pages; - pfn += P2M_ENTRIES_PER_PAGE) { + for(pfn = 0; pfn < max_pfn; pfn += P2M_ENTRIES_PER_PAGE) { unsigned topidx = p2m_top_index(pfn);

p2m_top[topidx] = &mfn_list[pfn]; @@ -96,6 +87,9 @@ unsigned long get_phys_to_machine(unsigned long pfn) { unsigned topidx, idx; + + if (unlikely(pfn >= MAX_DOMAIN_PAGES)) + return INVALID_P2M_ENTRY;

topidx = p2m_top_index(pfn); if (p2m_top[topidx] == NULL) @@ -126,6 +120,11 @@

if (unlikely(xen_feature(XENFEAT_auto_translated_physmap))) { BUG_ON(pfn != mfn && mfn != INVALID_P2M_ENTRY); + return; + } + + if (unlikely(pfn >= MAX_DOMAIN_PAGES)) { + BUG_ON(mfn != INVALID_P2M_ENTRY); return; }

diff --git a/arch/x86/xen/setup.c b/arch/x86/xen/setup.c --- a/arch/x86/xen/setup.c +++ b/arch/x86/xen/setup.c @@ -16,6 +16,7 @@ #include <asm/xen/hypervisor.h> #include <asm/xen/hypercall.h>

+#include <xen/page.h> #include <xen/interface/callback.h> #include <xen/interface/physdev.h> #include <xen/features.h> @@ -35,6 +36,8 @@ char * __init xen_memory_setup(void) { unsigned long max_pfn = xen_start_info->nr_pages; + + max_pfn = min(MAX_DOMAIN_PAGES, max_pfn);

e820.nr_map = 0; add_memory_region(0, LOWMEMSIZE(), E820_RAM); diff --git a/include/asm-x86/xen/page.h b/include/asm-x86/xen/page.h --- a/include/asm-x86/xen/page.h +++ b/include/asm-x86/xen/page.h @@ -25,6 +25,11 @@ #define INVALID_P2M_ENTRY (~0UL) #define FOREIGN_FRAME_BIT (1UL<<31) #define FOREIGN_FRAME(m) ((m) | FOREIGN_FRAME_BIT) + +/* Maximum amount of memory we can handle in a domain in pages */ +#define MAX_DOMAIN_PAGES \ + ((unsigned long)((u64)CONFIG_XEN_MAX_DOMAIN_MEMORY * 1024 * 1024 * 1024 /
PAGE_SIZE)) +

extern unsigned long get_phys_to_machine(unsigned long pfn); extern void set_phys_to_machine(unsigned long pfn, unsigned long mfn);