Re: [PATCH v2 2/2] KVM: s390: fix for hugepage vmalloc

[Christian Borntraeger]

On 08.06.21 20:06, Claudio Imbrenda wrote:
> The Create Secure Configuration Ultravisor Call does not support using
> large pages for the virtual memory area. This is a hardware limitation.
>
> This patch replaces the vzalloc call with a longer but equivalent
> __vmalloc_node_range call, also setting the VM_NO_HUGE_VMAP flag, to
> guarantee that this allocation will not be performed with large pages.
>
> Signed-off-by: Claudio Imbrenda <imbrenda@xxxxxxxxxxxxx>
> Reviewed-by: Janosch Frank <frankja@xxxxxxxxxxxxx>
> Fixes: 121e6f3258fe393e22c3 ("mm/vmalloc: hugepage vmalloc mappings")
> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> Cc: Nicholas Piggin <npiggin@xxxxxxxxx>
> Cc: Uladzislau Rezki (Sony) <urezki@xxxxxxxxx>
> Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> Cc: Ingo Molnar <mingo@xxxxxxxxxx>
> Cc: David Rientjes <rientjes@xxxxxxxxxx>

Would be good to have this in 5.13, as for everything else we want to have
hugepages in vmalloc space on s390.

In case Andrew picks this up
Acked-by: Christian Borntraeger <borntraeger@xxxxxxxxxx>
for the KVM/390 part.

> ---
>   arch/s390/kvm/pv.c | 5 ++++-
>   1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/arch/s390/kvm/pv.c b/arch/s390/kvm/pv.c
> index 813b6e93dc83..6087fe7ae77c 100644
> --- a/arch/s390/kvm/pv.c
> +++ b/arch/s390/kvm/pv.c
> @@ -140,7 +140,10 @@ static int kvm_s390_pv_alloc_vm(struct kvm *kvm)
>   	/* Allocate variable storage */
>   	vlen = ALIGN(virt * ((npages * PAGE_SIZE) / HPAGE_SIZE), PAGE_SIZE);
>   	vlen += uv_info.guest_virt_base_stor_len;
> -	kvm->arch.pv.stor_var = vzalloc(vlen);
> +	kvm->arch.pv.stor_var = __vmalloc_node_range(vlen, PAGE_SIZE, VMALLOC_START, VMALLOC_END,
> +						     GFP_KERNEL | __GFP_ZERO, PAGE_KERNEL,
> +						     VM_NO_HUGE_VMAP, NUMA_NO_NODE,
> +						     __builtin_return_address(0));
>   	if (!kvm->arch.pv.stor_var)
>   		goto out_err;
>   	return 0;