Default phys-bits on Qemu is TCG_PHYS_BITS (40) which is enough to address 1Tb (0xff ffff ffff). On AMD platforms, if a ram-above-4g relocation happens and the CPU wasn't configured with a big enough phys-bits, warn the user. There isn't a catastrophic failure exactly, the guest will still boot, but most likely won't be able to use more than ~4G of RAM.
Signed-off-by: Joao Martins <joao.m.mart...@oracle.com> --- hw/i386/pc.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/hw/i386/pc.c b/hw/i386/pc.c index b060aedd38f3..f8712eb8427e 100644 --- a/hw/i386/pc.c +++ b/hw/i386/pc.c @@ -842,6 +842,7 @@ static void relocate_4g(MachineState *machine, PCMachineState *pcms) X86MachineState *x86ms = X86_MACHINE(pcms); ram_addr_t device_mem_size = 0; uint32_t eax, vendor[3]; + hwaddr maxphysaddr; host_cpuid(0x0, 0, &eax, &vendor[0], &vendor[2], &vendor[1]); if (!IS_AMD_VENDOR(vendor)) { @@ -858,6 +859,12 @@ static void relocate_4g(MachineState *machine, PCMachineState *pcms) return; } + maxphysaddr = ((hwaddr)1 << X86_CPU(first_cpu)->phys_bits) - 1; + if (maxphysaddr < AMD_ABOVE_1TB_START) + warn_report("Relocated RAM above 4G to start at %lu " + "phys-bits too low (%u)", + AMD_ABOVE_1TB_START, X86_CPU(first_cpu)->phys_bits); + x86ms->above_4g_mem_start = AMD_ABOVE_1TB_START; } -- 2.17.2