Re: + kvm-s390-fix-for-hugepage-vmalloc.patch added to -mm tree

[Nicholas Piggin <npiggin@gmail.com>]

Excerpts from akpm@linux-foundation.org's message of June 9, 2021 7:06 am:
> 
> The patch titled
>      Subject: KVM: s390: fix for hugepage vmalloc
> has been added to the -mm tree.  Its filename is
>      kvm-s390-fix-for-hugepage-vmalloc.patch
> 
> This patch should soon appear at
>     https://ozlabs.org/~akpm/mmots/broken-out/kvm-s390-fix-for-hugepage-vmalloc.patch
> and later at
>     https://ozlabs.org/~akpm/mmotm/broken-out/kvm-s390-fix-for-hugepage-vmalloc.patch
> 
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> 
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> 
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> 
> ------------------------------------------------------
> From: Claudio Imbrenda <imbrenda@linux.ibm.com>
> Subject: KVM: s390: fix for hugepage vmalloc
> 
> 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.
> 
> Link: https://lkml.kernel.org/r/20210608180618.477766-3-imbrenda@linux.ibm.com
> Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
> Reviewed-by: Janosch Frank <frankja@linux.ibm.com>
> Fixes: 121e6f3258fe393e22c3 ("mm/vmalloc: hugepage vmalloc mappings")

Hmm, s390 does not select HAVE_ARCH_HUGE_VMALLOC so it was intended that 
"mm/vmalloc: hugepage vmalloc mappings" does not introduce huge vmallocs
for you.

I can't see how this would happen, any clue what I'm missing?

Thanks,
Nick

> Acked-by: Christian Borntraeger <borntraeger@de.ibm.com>	[s390]
> Cc: Nicholas Piggin <npiggin@gmail.com>
> Cc: Uladzislau Rezki (Sony) <urezki@gmail.com>
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: David Rientjes <rientjes@google.com>
> Cc: Janosch Frank <frankja@linux.ibm.com>
> Cc: David Hildenbrand <david@redhat.com>
> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
> ---
> 
>  arch/s390/kvm/pv.c |    5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> --- a/arch/s390/kvm/pv.c~kvm-s390-fix-for-hugepage-vmalloc
> +++ a/arch/s390/kvm/pv.c
> @@ -140,7 +140,10 @@ static int kvm_s390_pv_alloc_vm(struct k
>  	/* 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;
> _
> 
> Patches currently in -mm which might be from imbrenda@linux.ibm.com are
> 
> mm-vmalloc-export-__vmalloc_node_range.patch
> kvm-s390-fix-for-hugepage-vmalloc.patch
> 
>