Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Subject: Re: [PATCH v3 2/2] KVM: s390: fix for hugepage vmalloc
To:     Claudio Imbrenda <imbrenda@linux.ibm.com>
Cc:     linux-kernel@vger.kernel.org, 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>
 <368cfb74-fdc2-00a7-d452-696e375c2ff7@de.ibm.com>
 <20210610184953.19bed6b4@ibm-vm>
From:   Christian Borntraeger <borntraeger@de.ibm.com>
Message-ID: <7001a6a9-d415-e826-9bf0-17032568e7b3@de.ibm.com>
Date:   Thu, 10 Jun 2021 18:52:18 +0200
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101
 Thunderbird/78.10.0
MIME-Version: 1.0
In-Reply-To: <20210610184953.19bed6b4@ibm-vm>
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Language: en-US
Content-Transfer-Encoding: 7bit
Precedence: bulk


On 10.06.21 18:49, Claudio Imbrenda wrote:
> On Thu, 10 Jun 2021 17:56:58 +0200
> Christian Borntraeger <borntraeger@de.ibm.com> wrote:
> 
>> 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.
> 
> ^ here
> 
>>> 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?
> 
> no, as explained above

Makes sense.

Acked-by: Christian Borntraeger <borntraeger@de.ibm.com>