Re: [PATCH 0/8] arm64: ARMv8.5-A: Branch Target Identification support
From: Dave Martin <Dave.Martin@arm.com>
Date: 2019-06-06 09:34:36
On Wed, Jun 05, 2019 at 04:12:03PM -0500, Richard Henderson wrote:
On 5/24/19 5:25 AM, Dave Martin wrote:quoted
Various things need nailing down before this can be upstreamable: * Not tested with hugepages yet. (If anyone has any suggestions about how best to do that, please shout!)The qemu code_gen_buffer is generally between 32MB and 2GB, contiguous. It usually gets AnonHugePage'd. I assume there's no difference in where the hugepages come from on your side?
There are some internal differences between hugetlbfs and anonymous huge pages, but I'm not very familiar with the details.
It won't be too difficult to modify qemu to make it's own code generation BTI-safe, and is on the schedule to do eventually anyway.
For userspace, it really shouldn't make a difference where the pages come from. With hugetlbfs, probably mprotect() only works at huge page granularity; for anonymous huge pages, mprotect() should work at page granularity, with the kernel shattering huge pages as required. I guess I can come up with a handcrafted test or two. Cheers ---Dave _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel