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

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Date:   Tue, 8 Jun 2021 20:52:53 +0200
From:   Christian Borntraeger <borntraeger@...ibm.com>
To:     Claudio Imbrenda <imbrenda@...ux.ibm.com>,
        linux-kernel@...r.kernel.org
Cc:     kvm@...r.kernel.org, linux-s390@...r.kernel.org,
        frankja@...ux.ibm.com, cohuck@...hat.com, david@...hat.com,
        linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
        Nicholas Piggin <npiggin@...il.com>,
        Uladzislau Rezki <urezki@...il.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        David Rientjes <rientjes@...gle.com>
Subject: Re: [PATCH v2 2/2] KVM: s390: fix for hugepage vmalloc


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@...ux.ibm.com>
> Reviewed-by: Janosch Frank <frankja@...ux.ibm.com>
> Fixes: 121e6f3258fe393e22c3 ("mm/vmalloc: hugepage vmalloc mappings")
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: Nicholas Piggin <npiggin@...il.com>
> Cc: Uladzislau Rezki (Sony) <urezki@...il.com>
> Cc: Catalin Marinas <catalin.marinas@....com>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: Ingo Molnar <mingo@...hat.com>
> Cc: David Rientjes <rientjes@...gle.com>

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@...ibm.com>
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;
>