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Subject: Re: [PATCH v3 2/2] KVM: s390: fix for hugepage vmalloc
To:     Claudio Imbrenda <imbrenda@linux.ibm.com>,
        linux-kernel@vger.kernel.org
Cc:     kvm@vger.kernel.org, linux-s390@vger.kernel.org,
        frankja@linux.ibm.com, cohuck@redhat.com, david@redhat.com,
        linux-mm@kvack.org, Andrew Morton <akpm@linux-foundation.org>,
        Nicholas Piggin <npiggin@gmail.com>,
        Uladzislau Rezki <urezki@gmail.com>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>,
        David Rientjes <rientjes@google.com>,
        Christoph Hellwig <hch@infradead.org>
References: <20210610154220.529122-1-imbrenda@linux.ibm.com>
 <20210610154220.529122-3-imbrenda@linux.ibm.com>
From:   Christian Borntraeger <borntraeger@de.ibm.com>
Message-ID: <368cfb74-fdc2-00a7-d452-696e375c2ff7@de.ibm.com>
Date:   Thu, 10 Jun 2021 17:56:58 +0200
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On 10.06.21 17:42, 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@linux.ibm.com>
> Reviewed-by: Janosch Frank <frankja@linux.ibm.com>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> 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: Christoph Hellwig <hch@infradead.org>
> ---
>   arch/s390/kvm/pv.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/s390/kvm/pv.c b/arch/s390/kvm/pv.c
> index 813b6e93dc83..ad7c6d7cc90b 100644
> --- a/arch/s390/kvm/pv.c
> +++ b/arch/s390/kvm/pv.c
> @@ -140,7 +140,7 @@ 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_no_huge(vlen);

dont we need a memset now?

>   	if (!kvm->arch.pv.stor_var)
>   		goto out_err;
>   	return 0;
>