Re: [PATCH] x86: cpu: Error out if memory exceeds addressable range

[Igor Mammedov]

On Mon, 18 Jul 2022 13:47:34 +0530
Nikunj A Dadhania <nikunj@amd.com> wrote:

> Currently it is possible to start a guest with memory that is beyond
> the addressable range of CPU and QEMU does not even warn about it.
> The default phys_bits is 40 and can address 1TB. However it allows to
> start a guest with greater than 1TB memory.
> 
> Prevent this by erroring out in such a scenario.
> 
> Reported-by: Shaju Abraham <Abraham.Shaju@amd.com>
> Signed-off-by: Nikunj A Dadhania <nikunj@amd.com>


Following shall care of your issue:
https://www.mail-archive.com/qemu-devel@nongnu.org/msg900136.html

> ---
>  target/i386/cpu.c | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/target/i386/cpu.c b/target/i386/cpu.c
> index 6a57ef13af..1afbdbac7d 100644
> --- a/target/i386/cpu.c
> +++ b/target/i386/cpu.c
> @@ -6376,6 +6376,7 @@ static void x86_cpu_hyperv_realize(X86CPU *cpu)
>  
>  static void x86_cpu_realizefn(DeviceState *dev, Error **errp)
>  {
> +    MachineState *machine = MACHINE(qdev_get_machine());
>      CPUState *cs = CPU(dev);
>      X86CPU *cpu = X86_CPU(dev);
>      X86CPUClass *xcc = X86_CPU_GET_CLASS(dev);
> @@ -6541,6 +6542,15 @@ static void x86_cpu_realizefn(DeviceState *dev, Error 
> **errp)
>          }
>      }
>  
> +    if (BIT_ULL(cpu->phys_bits) < machine->maxram_size) {
> +        error_setg(&local_err, "cannot setup guest memory: "
> +                   "%s memory(%lu MiB) exceeds addressable limit(%llu MiB)",
> +                   machine->maxram_size == machine->ram_size ? "" : "max",
> +                   machine->maxram_size / MiB,
> +                   BIT_ULL(cpu->phys_bits) / MiB);
> +        goto out;
> +    }
> +
>      /* Cache information initialization */
>      if (!cpu->legacy_cache) {
>          if (!xcc->model || !xcc->model->cpudef->cache_info) {