Re: [RFC PATCH 4/5] EXPERIMENTAL: x86: use __GFP_UNMAPPED for modele_alloc()

From: "Edgecombe, Rick P" <rick.p.edgecombe@intel.com>
To: "linux-mm@kvack.org" <linux-mm@kvack.org>,
	"rppt@kernel.org" <rppt@kernel.org>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"peterz@infradead.org" <peterz@infradead.org>,
	"tglx@linutronix.de" <tglx@linutronix.de>,
	"song@kernel.org" <song@kernel.org>,
	"dave.hansen@linux.intel.com" <dave.hansen@linux.intel.com>,
	"vbabka@suse.cz" <vbabka@suse.cz>,
	"x86@kernel.org" <x86@kernel.org>,
	"akpm@linux-foundation.org" <akpm@linux-foundation.org>
Subject: Re: [RFC PATCH 4/5] EXPERIMENTAL: x86: use __GFP_UNMAPPED for modele_alloc()
Date: Thu, 9 Mar 2023 01:54:30 +0000	[thread overview]
Message-ID: <ba3e16e1e2d6b2f5eae54d41592f90c9e7827241.camel@intel.com> (raw)
In-Reply-To: <20230308094106.227365-5-rppt@kernel.org>

On Wed, 2023-03-08 at 11:41 +0200, Mike Rapoport wrote:
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index ef910bf349e1..84220ec45ec2 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -2892,7 +2892,7 @@ vm_area_alloc_pages(gfp_t gfp, int nid,
>          * to fails, fallback to a single page allocator that is
>          * more permissive.
>          */
> -       if (!order) {
> +       if (!order && !(gfp & __GFP_UNMAPPED)) {
>                 gfp_t bulk_gfp = gfp & ~__GFP_NOFAIL;
>  
>                 while (nr_allocated < nr_pages) {

This is obviously a quick POC patch, but I guess we should skip the
whole vm_remove_mappings() thing since it would reset the direct map to
RW for these unmapped pages. Or rather modules shouldn't set
VM_FLUSH_RESET_PERMS if it uses this.