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References: <1458768723-89242-1-git-send-email-dingel@linux.vnet.ibm.com>
From: Paolo Bonzini <pbonzini@redhat.com>
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Date: Thu, 24 Mar 2016 12:35:10 +0100
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Subject: Re: [Qemu-devel] [PATCH] exec.c: Ensure right alignment also for
	file backed ram
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To: Dominik Dingel <dingel@linux.vnet.ibm.com>, qemu-devel@nongnu.org
Cc: Halil Pasic <pasic@linux.vnet.ibm.com>, Richard Henderson <rth@twiddle.net>, Peter Crosthwaite <crosthwaite.peter@gmail.com>



On 23/03/2016 22:32, Dominik Dingel wrote:
> -    page_size = qemu_fd_getpagesize(fd);
> -    block->mr->align = page_size;
> +    alignment = MAX(qemu_fd_getpagesize(fd), QEMU_VMALLOC_ALIGN);
> +    block->mr->align = alignment;
>  
> -    if (memory < page_size) {
> +    if (memory < alignment) {
>          error_setg(errp, "memory size 0x" RAM_ADDR_FMT " must be equal to "
> -                   "or larger than page size 0x%" PRIx64,
> -                   memory, page_size);
> +                   "or larger than needed alignment 0x%" PRIx64,
> +                   memory, alignment);
>          goto error;
>      }

Why is this part necessary?  On x86 you can have 1 megabyte of RAM,
but QEMU_VMALLOC_ALIGN is 2MB.

Paolo

> -    memory = ROUND_UP(memory, page_size);
> +    memory = ROUND_UP(memory, alignment);
>