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From: Peter Maydell <peter.maydell@linaro.org>
Date: Fri, 22 Apr 2016 11:17:47 +0100
Message-ID: <CAFEAcA__CQ=Vjra2pfYBhUeWW_g4Sv+dwyuPQy_46Z3nha+Czg@mail.gmail.com>
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Subject: Re: [Qemu-devel] Performance regression using KVM/ARM
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To: Christoffer Dall <christoffer.dall@linaro.org>
Cc: Alexander Graf <agraf@suse.de>, "Michael S. Tsirkin" <mst@redhat.com>, QEMU Developers <qemu-devel@nongnu.org>, Marc Zyngier <marc.zyngier@arm.com>, Paolo Bonzini <pbonzini@redhat.com>

On 22 April 2016 at 11:15, Christoffer Dall <christoffer.dall@linaro.org> wrote:
> Peter just pointed me to a change I remember doing for ARM, so perhaps
> this fix is the right one?
>
>
> diff --git a/util/oslib-posix.c b/util/oslib-posix.c
> index d25f671..a36e734 100644
> --- a/util/oslib-posix.c
> +++ b/util/oslib-posix.c
> @@ -35,7 +35,7 @@
>  extern int daemon(int, int);
>  #endif
>
> -#if defined(__linux__) && (defined(__x86_64__) || defined(__arm__))
> +#if defined(__linux__) && (defined(__x86_64__) || defined(__arm__)) || defined(__aarch64__)
>     /* Use 2 MiB alignment so transparent hugepages can be used by KVM.
>        Valgrind does not support alignments larger than 1 MiB,
>        therefore we need special code which handles running on Valgrind. */

I hadn't realised AArch64 didn't define __arm__. Your extra clause
wants to be inside the parens for the ||, not outside.

So was the problem just that we weren't passing 2MB as the align
parameter to qemu_ram_mmap(), and if we do pass 2MB then it does the
right thing ?

thanks
-- PMM