Re: [Qemu-devel] [PATCH v6 10/18] hw/arm/virt: Bump the 255GB initial RAM limit

[Shameerali Kolothum Thodi <shameerali.kolothum.thodi@huawei.com>]

Hi Eric,

> -----Original Message-----
> From: Eric Auger [mailto:eric.auger@redhat.com]
> Sent: 05 February 2019 17:33
> To: eric.auger.pro@gmail.com; eric.auger@redhat.com;
> qemu-devel@nongnu.org; qemu-arm@nongnu.org; peter.maydell@linaro.org;
> Shameerali Kolothum Thodi <shameerali.kolothum.thodi@huawei.com>;
> imammedo@redhat.com; david@redhat.com
> Cc: dgilbert@redhat.com; david@gibson.dropbear.id.au; drjones@redhat.com
> Subject: [PATCH v6 10/18] hw/arm/virt: Bump the 255GB initial RAM limit
> 
> Now we have the extended memory map (high IO regions beyond the
> scalable RAM) and dynamic IPA range support at KVM/ARM level
> we can bump the legacy 255GB initial RAM limit. The actual maximum
> RAM size now depends on the physical CPU and host kernel.
> 
> Signed-off-by: Eric Auger <eric.auger@redhat.com>
> ---
>  hw/arm/virt.c | 26 +++++++-------------------
>  1 file changed, 7 insertions(+), 19 deletions(-)
> 
> diff --git a/hw/arm/virt.c b/hw/arm/virt.c
> index b90ffc2e5d..f01886da22 100644
> --- a/hw/arm/virt.c
> +++ b/hw/arm/virt.c
> @@ -93,22 +93,9 @@
> 
>  #define PLATFORM_BUS_NUM_IRQS 64
> 
> -/* RAM limit in GB. Since VIRT_MEM starts at the 1GB mark, this means
> - * RAM can go up to the 256GB mark, leaving 256GB of the physical
> - * address space unallocated and free for future use between 256G and 512G.
> - * If we need to provide more RAM to VMs in the future then we need to:
> - *  * allocate a second bank of RAM starting at 2TB and working up
> - *  * fix the DT and ACPI table generation code in QEMU to correctly
> - *    report two split lumps of RAM to the guest
> - *  * fix KVM in the host kernel to allow guests with >40 bit address spaces
> - * (We don't want to fill all the way up to 512GB with RAM because
> - * we might want it for non-RAM purposes later. Conversely it seems
> - * reasonable to assume that anybody configuring a VM with a quarter
> - * of a terabyte of RAM will be doing it on a host with more than a
> - * terabyte of physical address space.)
> - */
> -#define RAMLIMIT_GB 255
> -#define RAMLIMIT_BYTES (RAMLIMIT_GB * 1024ULL * 1024 * 1024)
> +/* Legacy RAM limit in GB (< version 4.0) */
> +#define LEGACY_RAMLIMIT_GB 255
> +#define LEGACY_RAMLIMIT_BYTES (LEGACY_RAMLIMIT_GB * GiB)
> 
>  /* Addresses and sizes of our components.
>   * 0..128MB is space for a flash device so we can run bootrom code such as
> UEFI.
> @@ -149,7 +136,7 @@ static const MemMapEntry a15memmap[] = {
>      [VIRT_PCIE_MMIO] =          { 0x10000000, 0x2eff0000 },
>      [VIRT_PCIE_PIO] =           { 0x3eff0000, 0x00010000 },
>      [VIRT_PCIE_ECAM] =          { 0x3f000000, 0x01000000 },
> -    [VIRT_MEM] =                { 0x40000000, RAMLIMIT_BYTES },
> +    [VIRT_MEM] =                { 0x40000000,
> LEGACY_RAMLIMIT_BYTES },
>  };
> 
>  /*
> @@ -1483,8 +1470,9 @@ static void machvirt_init(MachineState *machine)
> 
>      vms->smp_cpus = smp_cpus;
> 
> -    if (machine->ram_size > vms->memmap[VIRT_MEM].size) {
> -        error_report("mach-virt: cannot model more than %dGB RAM",
> RAMLIMIT_GB);
> +    if (!vms->extended_memmap && machine->ram_size >
> LEGACY_RAMLIMIT_GB) {

Just hit this while testing, should this check be against LEGACY_RAMLIMIT_BYTES?

Thanks,
Shameer

> +        error_report("mach-virt: cannot model more than %dGB RAM",
> +                     LEGACY_RAMLIMIT_GB);
>          exit(1);
>      }
> 
> --
> 2.20.1