linux-kernel - Re: hv_hypercall

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Message-ID: <20200616102050.GP2531@hirez.programming.kicks-ass.net>
Date:   Tue, 16 Jun 2020 12:20:50 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Christoph Hellwig <hch@....de>
Cc:     Vitaly Kuznetsov <vkuznets@...hat.com>,
        Dexuan Cui <decui@...rosoft.com>,
        Stephen Hemminger <stephen@...workplumber.org>,
        Andy Lutomirski <luto@...nel.org>,
        Andy Lutomirski <luto@...capital.net>,
        Michael Kelley <mikelley@...rosoft.com>,
        Ju-Hyoung Lee <juhlee@...rosoft.com>,
        "x86@...nel.org" <x86@...nel.org>,
        "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        KY Srinivasan <kys@...rosoft.com>
Subject: Re: hv_hypercall_pg page permissios

On Tue, Jun 16, 2020 at 11:55:49AM +0200, Christoph Hellwig wrote:
> +	hv_hypercall_pg = __vmalloc_node_range(PAGE_SIZE, 1, VMALLOC_START,
> +			VMALLOC_END, GFP_KERNEL, PAGE_KERNEL_RX,
> +			VM_FLUSH_RESET_PERMS, NUMA_NO_NODE, __func__);

I think that's wrong, they seem to want to CALL into that page, and that
doesn't unconditionally work for any page in the vmalloc range. This
really ought to use module_alloc() to guarantees it gets a page in the
correct range.