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Subject: Re: [kvm PATCH v4 0/2] use vmalloc to allocate vmx vcpus
References: <20181026075900.111462-1-marcorr@google.com>
 <20181026122948.GQ25444@bombadil.infradead.org>
 <20181026144528.GS25444@bombadil.infradead.org>
From: Dave Hansen <dave.hansen@intel.com>
Message-ID: <cd9934d3-2699-d705-9e66-88485fc74ead@intel.com>
Date: Fri, 26 Oct 2018 07:49:09 -0700
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To: Matthew Wilcox <willy@infradead.org>, Marc Orr <marcorr@google.com>
Cc: kvm@vger.kernel.org, jmattson@google.com, rientjes@google.com, konrad.wilk@oracle.com, linux-mm@kvack.org, akpm@linux-foundation.org, pbonzini@redhat.com, rkrcmar@redhat.com, sean.j.christopherson@intel.com, Dave Hansen <dave.hansen@linux.intel.com>

On 10/26/18 7:45 AM, Matthew Wilcox wrote:
>         struct fpu                 user_fpu;             /*  2176  4160 */
>         struct fpu                 guest_fpu;            /*  6336  4160 */

Those are *not* supposed to be embedded in any other structures.  My bad
for not documenting this better.

It also seems really goofy that we need an xsave buffer in the
task_struct for user fpu state, then another in the vcpu.  Isn't one for
user state enough?

In any case, I'd suggest getting rid of 'user_fpu', then either moving
'guest_fpu' to the bottom of the structure, or just make it a 'struct
fpu *' and dynamically allocating it separately.

To do this, I'd take fpu__init_task_struct_size(), and break it apart a
bit to tell you the size of the 'struct fpu' separately from the size of
the 'task struct'.