linux-kernel - Re: [PATCH v4 2/2] KVM: s390: prepare for hugepage vmalloc

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Date:   Mon, 14 Jun 2021 15:44:43 +0200
From:   David Hildenbrand <david@...hat.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, borntraeger@...ibm.com, cohuck@...hat.com,
        linux-mm@...ck.org, Nicholas Piggin <npiggin@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        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>,
        Christoph Hellwig <hch@...radead.org>
Subject: Re: [PATCH v4 2/2] KVM: s390: prepare for hugepage vmalloc

On 14.06.21 15:23, 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 an almost equivalent call to
> the newly introduced vmalloc_no_huge function, which guarantees that
> only small pages will be used for the backing.
> 
> The new call will not clear the allocated memory, but that has never
> been an actual requirement.
> 
> Signed-off-by: Claudio Imbrenda <imbrenda@...ux.ibm.com>
> Reviewed-by: Janosch Frank <frankja@...ux.ibm.com>
> Acked-by: Christian Borntraeger <borntraeger@...ibm.com>
> Acked-by: Nicholas Piggin <npiggin@...il.com>
> 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>
> Cc: Christoph Hellwig <hch@...radead.org>
> ---
>   arch/s390/kvm/pv.c | 7 ++++++-
>   1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/s390/kvm/pv.c b/arch/s390/kvm/pv.c
> index 813b6e93dc83..c8841f476e91 100644
> --- a/arch/s390/kvm/pv.c
> +++ b/arch/s390/kvm/pv.c
> @@ -140,7 +140,12 @@ 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);
> +	/*
> +	 * The Create Secure Configuration Ultravisor Call does not support
> +	 * using large pages for the virtual memory area.
> +	 * This is a hardware limitation.
> +	 */
> +	kvm->arch.pv.stor_var = vmalloc_no_huge(vlen);
>   	if (!kvm->arch.pv.stor_var)
>   		goto out_err;
>   	return 0;
> 

Reviewed-by: David Hildenbrand <david@...hat.com>

-- 
Thanks,

David / dhildenb