Re: [kvm PATCH v4 0/2] use vmalloc to allocate vmx vcpus

[Matthew Wilcox <willy@infradead.org>]

On Fri, Oct 26, 2018 at 12:58:58AM -0700, Marc Orr wrote:
> A couple of patches to allocate vmx vcpus with vmalloc instead of
> kalloc, which enables vcpu allocation to succeeed when contiguous
> physical memory is sparse.

A question that may have been asked already, but if so I didn't see it ...
does kvm_vcpu need to be so damn big?  It's 22kB with the random .config
I happen to have (which gets rounded to 32kB, an order-3 allocation).  If
we can knock 6kB off it (either by allocating pieces separately), it becomes
an order-2 allocation.  So, biggest chunks:

        struct kvm_vcpu_arch       arch;                 /*   576 21568 */

        struct kvm_mmu             mmu;                  /*   336   400 */
        struct kvm_mmu             nested_mmu;           /*   736   400 */
        struct fpu                 user_fpu;             /*  2176  4160 */
        struct fpu                 guest_fpu;            /*  6336  4160 */
        struct kvm_cpuid_entry2    cpuid_entries[80];    /* 10580  3200 */
        struct x86_emulate_ctxt    emulate_ctxt;         /* 13792  2656 */
        struct kvm_pmu             pmu;                  /* 17344  1520 */
        struct kvm_vcpu_hv         hyperv;               /* 18872  1872 */
                gfn_t              gfns[64];             /* 20832   512 */

that's about 19kB of the 22kB right there.  Can any of them be shrunk
in size or allocated separately?