From c87b1520726f7ae1e698a41f07043d1b539ac88c Mon Sep 17 00:00:00 2001 From: Don Slutz Date: Thu, 19 Jun 2014 21:40:25 -0400 Subject: pc & q35: Add new machine opt max-ram-below-4g This is a pc & q35 only machine opt. If you add enough PCI devices then all mmio for them will not fit below 4G which may not be the layout the user wanted. This allows you to increase the below 4G address space that PCI devices can use (aka decrease ram below 4G) and therefore in more cases not have any mmio that is above 4G. For example using "-machine pc,max-ram-below-4g=2G" on the command line will limit the amount of ram that is below 4G to 2G. Note: this machine option cannot be used to increase the amount of ram below 4G. Signed-off-by: Don Slutz Reviewed-by: Michael S. Tsirkin Signed-off-by: Michael S. Tsirkin MST: fix 32 bit --- hw/i386/pc_q35.c | 22 +++++++++++++++++++++- 1 file changed, 21 insertions(+), 1 deletion(-) (limited to 'hw/i386/pc_q35.c') diff --git a/hw/i386/pc_q35.c b/hw/i386/pc_q35.c index da5fd53..155db99 100644 --- a/hw/i386/pc_q35.c +++ b/hw/i386/pc_q35.c @@ -44,6 +44,7 @@ #include "hw/ide/ahci.h" #include "hw/usb.h" #include "hw/cpu/icc_bus.h" +#include "qemu/error-report.h" /* ICH9 AHCI has 6 ports */ #define MAX_SATA_PORTS 6 @@ -85,6 +86,7 @@ static void pc_q35_init(MachineState *machine) PCIDevice *ahci; DeviceState *icc_bridge; PcGuestInfo *guest_info; + ram_addr_t lowmem; /* Check whether RAM fits below 4G (leaving 1/2 GByte for IO memory * and 256 Mbytes for PCI Express Enhanced Configuration Access Mapping @@ -96,7 +98,25 @@ static void pc_q35_init(MachineState *machine) * breaking migration. */ if (machine->ram_size >= 0xb0000000) { - ram_addr_t lowmem = gigabyte_align ? 0x80000000 : 0xb0000000; + lowmem = gigabyte_align ? 0x80000000 : 0xb0000000; + } else { + lowmem = 0xb0000000; + } + + /* Handle the machine opt max-ram-below-4g. It is basicly doing + * min(qemu limit, user limit). + */ + if (lowmem > pc_machine->max_ram_below_4g) { + lowmem = pc_machine->max_ram_below_4g; + if (machine->ram_size - lowmem > lowmem && + lowmem & ((1ULL << 30) - 1)) { + error_report("Warning: Large machine and max_ram_below_4g(%"PRIu64 + ") not a multiple of 1G; possible bad performance.", + pc_machine->max_ram_below_4g); + } + } + + if (machine->ram_size >= lowmem) { above_4g_mem_size = machine->ram_size - lowmem; below_4g_mem_size = lowmem; } else { -- cgit v1.1