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Date: Wed, 31 Oct 2018 07:21:22 -0700
From: Matthew Wilcox <willy@infradead.org>
Subject: Re: [kvm PATCH v4 0/2] use vmalloc to allocate vmx vcpus
Message-ID: <20181031142122.GM10491@bombadil.infradead.org>
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Sender: owner-linux-mm@kvack.org
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To: Marc Orr <marcorr@google.com>
Cc: Jim Mattson <jmattson@google.com>, Wanpeng Li <kernellwp@gmail.com>, kvm@vger.kernel.org, David Rientjes <rientjes@google.com>, Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>, linux-mm@kvack.org, akpm@linux-foundation.org, pbonzini@redhat.com, rkrcmar@redhat.com, sean.j.christopherson@intel.com

On Wed, Oct 31, 2018 at 01:48:44PM +0000, Marc Orr wrote:
> Thanks for the explanation. Is there a way to dynamically detect the
> memory allocation done by kvmalloc() (i.e., kmalloc() or vmalloc())?
> If so, we could use kvmalloc(), and add two code paths to do the
> physical mapping, according to whether the underlying memory was
> allocated with kmalloc() or vmalloc().

Yes -- it's used in the implementation of kvfree():

        if (is_vmalloc_addr(addr))
                vfree(addr);
        else
                kfree(addr);