Date: Tue, 3 May 2011 11:44:32 -0400 From: John Baldwin <jhb@freebsd.org> To: freebsd-hackers@freebsd.org, philip-freebsd1@soeberg.net Subject: Re: Runtime check for PAE option on BSD 6+ i386 Message-ID: <201105031144.32862.jhb@freebsd.org> In-Reply-To: <4DBFFEC2.4010506@soeberg.net> References: <4DBFFEC2.4010506@soeberg.net>
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On Tuesday, May 03, 2011 9:10:26 am Philip Soeberg wrote:
> Hi fellow FreeBSD hackers,
>
> I've been using the following poor-man's approach in my driver init for
> ages in an attempt at detecting PAE option on BSD 6 (or greater) i386
> kernels, as I depend on dmabus(9) but provide a loadable kernel module only.
>
> >>>
> if (sizeof(void*) == 4) {
> if (((uint64_t)(cnt.v_page_count * cnt.v_page_size) / 1073741824)
> >= 4) {
> printf("FreeBSD i386 detected with PAE option enabled. FreeBSD
> PAE type\n");
> printf("kernels does not support loadable modules which use DMA.
> Please\n");
> printf("reconfigure your kernel for non-PAE or switch to amd64
> kernel.\n");
> return EFAULT;
> }
> }
> <<<
Hmmm, even this isn't really accurate as some folks may choose to enable PAE
even with < 4GB to get PG_NX functionality.
> afaik there's a sysctl method of checking this per BSD7 (or is it 8?),
> but what about BSD6? Any hints on how I can runtime detect the above?
Definitely a kern.features.pae sysctl in 7. I don't see anything similar in
6.
--
John Baldwin
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