Re: [PATCH v2 3/5] hw/arm/virt: Honor highmem setting when computing the memory map

[Andrew Jones]

On Sun, Oct 03, 2021 at 05:46:03PM +0100, Marc Zyngier wrote:
> Even when the VM is configured with highmem=off, the highest_gpa
> field includes devices that are above the 4GiB limit.
> Similarily, nothing seem to check that the memory is within
> the limit set by the highmem=off option.
> 
> This leads to failures in virt_kvm_type() on systems that have
> a crippled IPA range, as the reported IPA space is larger than
> what it should be.
> 
> Instead, honor the user-specified limit to only use the devices
> at the lowest end of the spectrum, and fail if we have memory
> crossing the 4GiB limit.
> 
> Signed-off-by: Marc Zyngier <maz@kernel.org>
> ---
>  hw/arm/virt.c | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/hw/arm/virt.c b/hw/arm/virt.c
> index bcf58f677d..9d2abdbd5f 100644
> --- a/hw/arm/virt.c
> +++ b/hw/arm/virt.c
> @@ -1628,6 +1628,11 @@ static void virt_set_memmap(VirtMachineState *vms)
>          exit(EXIT_FAILURE);
>      }
>  
> +    if (!vms->highmem &&
> +        vms->memmap[VIRT_MEM].base + ms->maxram_size > 4 * GiB) {
> +        error_report("highmem=off, but memory crosses the 4GiB limit\n");
> +        exit(EXIT_FAILURE);
> +    }
>      /*
>       * We compute the base of the high IO region depending on the
>       * amount of initial and device memory. The device memory start/size
> @@ -1657,7 +1662,9 @@ static void virt_set_memmap(VirtMachineState *vms)
>          vms->memmap[i].size = size;
>          base += size;
>      }
> -    vms->highest_gpa = base - 1;
> +    vms->highest_gpa = (vms->highmem ?
> +                        base :
> +                        vms->memmap[VIRT_MEM].base + ms->maxram_size) - 1;
>      if (device_memory_size > 0) {
>          ms->device_memory = g_malloc0(sizeof(*ms->device_memory));
>          ms->device_memory->base = device_memory_base;
> -- 
> 2.30.2
>

Reviewed-by: Andrew Jones <drjones@redhat.com>