[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] query on physical memory map for Xen?
Nada, this is definetly the wrong piece of code you are looking at.:-) Let me check once again for you ... Ahh...got something. see xen/include/asm-x86/config.h 296 #ifdef CONFIG_X86_PAE 297 # define LINEARPT_MBYTES 8 298 # define MACHPHYS_MBYTES 16 /* 1 MB needed per 1 GB memory */ 299 # define FRAMETABLE_MBYTES (MACHPHYS_MBYTES * 6) 300 #else 301 # define LINEARPT_MBYTES 4 302 # define MACHPHYS_MBYTES 4 303 # define FRAMETABLE_MBYTES 24 a 32 bit kernel/hypervisor cannot access more than 4GB of physical memory.So if PAE is enabled while compiling the kernel/hypervisor you get the first part of the above conditional macro. for each GB you have 1MB of memory for a m2p table.isn't it? 16MB means 16GB of physical mem max you can address in 32 bit xen hypervisor. Thanks, On Mon, Apr 14, 2008 at 11:13 AM, Peter Teoh <htmldeveloper@xxxxxxxxx> wrote: > Just curious, can anyone give a hint on where this 16GB max physical > memory is defined? > > Doing some random search by strings I found these: > > #define MAXMEM 0x3fffffffffffUL > #define MAXMEM > (__FIXADDR_TOP-__PAGE_OFFSET-__VMALLOC_RESERVE) > #define MAXMEM_PFN PFN_DOWN(MAXMEM) > #define ACPI_MEM_LIST_MAX 6 > #define NR_NODE_MEMBLKS (MAX_NUMNODES*2) > #define EFI_MAX_MEMORY_TYPE 14 > #define PCI_X_CMD_MAX_READ 0x000c /* Max Memory Read Byte Count */ > #define PCI_X_STATUS_MAX_READ 0x00600000 /* Designed Max Memory > Read Count */ > #define GEO_TYPE_MAX (GEO_TYPE_MEM+1) > #define NR_NODE_MEMBLKS (MAX_NUMNODES*2) > *max_mfn = xc_memory_op(xc_handle, XENMEM_maximum_ram_page, NULL); > #define EFI_MAX_MEMORY_TYPE 14 > #define MAXMEM 0x3fffffffffffUL > * KEXEC_SOURCE_MEMORY_LIMIT maximum page get_free_page can return. > #define MAXMEM > (__FIXADDR_TOP-__PAGE_OFFSET-__VMALLOC_RESERVE) > #define MAXMEM_PFN PFN_DOWN(MAXMEM) > * KEXEC_SOURCE_MEMORY_LIMIT maximum page get_free_page can return. > #define ACPI_MEM_LIST_MAX 6 > #define XENMEM_maximum_ram_page 2 > #define XENMEM_maximum_reservation 4 > #define XENMEM_maximum_gpfn 14 > #define NR_NODE_MEMBLKS (MAX_NUMNODES*2) > #define EFI_MAX_MEMORY_TYPE 14 > #define GEO_TYPE_MAX (GEO_TYPE_MEM+1) > #define NR_NODE_MEMBLKS (MAX_NUMNODES*2) > > Not sure which one maps to this 16GB thing? Thanks for the sharing :-). > > > > On Fri, Apr 11, 2008 at 2:54 PM, Keir Fraser <keir.fraser@xxxxxxxxxxxxx> > wrote: > > On 11/4/08 07:14, "pradeep singh rautela" <rautelap@xxxxxxxxx> wrote: > > > > > Based on my understanding of the Xen code, I have a small query for you > all. > > > > > > Xen hypervisor can access only a max of 16GB of physical memory > > > directly on x86 architecture. > > > Is this correct inference? > > > > > > So does Xen hypervisor cannot touch memory about 16G directly? Does it > > > employ some kind of temporary mapping like linux kernel to access > > > memory above 16G then? > > > > 32-bit Xen does not use memory above 16GB at all. 64-bit Xen can use any > > amount of memory, and is able to keep a permanent mapping of all of it. > > > > -- Keir > > > > > > > > > > > > _______________________________________________ > > Xen-devel mailing list > > Xen-devel@xxxxxxxxxxxxxxxxxxx > > http://lists.xensource.com/xen-devel > > > > > > -- > Regards, > Peter Teoh > -- Pradeep Singh Rautela http://eagain.wordpress.com http://emptydomain.googlepages.com _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
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