Received-SPF: pass (google.com: domain of linux-kernel+bounces-72555-linux.lists.archive=gmail.com@vger.kernel.org designates 2604:1380:45d1:ec00::1 as permitted sender) client-ip=2604:1380:45d1:ec00::1;
Precedence: bulk
MIME-Version: 1.0
References: <20240215225116.3435953-1-boqun.feng@gmail.com>
 <2024021718-dwindling-oval-8183@gregkh> <ZdQmCEepdOE2R7gS@boqun-archlinux>
In-Reply-To: <ZdQmCEepdOE2R7gS@boqun-archlinux>
From: Ard Biesheuvel <ardb@kernel.org>
Date: Tue, 20 Feb 2024 09:27:54 +0100
Message-ID: <CAMj1kXGzaUsgn0DGfy15c+Z5ECNqosjWbci-YZyUTsMWXte21A@mail.gmail.com>
Subject: Re: [RFC] efi: Add ACPI_MEMORY_NVS into the linear map
To: Boqun Feng <boqun.feng@gmail.com>
Cc: Greg KH <gregkh@linuxfoundation.org>, linux-arm-kernel@vger.kernel.org, 
	stable@vger.kernel.org, linux-efi@vger.kernel.org, 
	linux-kernel@vger.kernel.org, Oliver Smith-Denny <osde@linux.microsoft.com>
Content-Type: text/plain; charset="UTF-8"

On Tue, 20 Feb 2024 at 05:10, Boqun Feng <boqun.feng@gmail.com> wrote:
>
> On Sat, Feb 17, 2024 at 08:49:32AM +0100, Greg KH wrote:
> > On Thu, Feb 15, 2024 at 02:51:06PM -0800, Boqun Feng wrote:
> > > Currently ACPI_MEMORY_NVS is omitted from the linear map, which causes
> > > a trouble with the following firmware memory region setup:
> > >
> > >     [..] efi:   0x0000dfd62000-0x0000dfd83fff [ACPI Reclaim|...]
> > >     [..] efi:   0x0000dfd84000-0x0000dfd87fff [ACPI Mem NVS|...]
> > >
> > > , on ARM64 with 64k page size, the whole 0x0000dfd80000-0x0000dfd8ffff
> > > range will be omitted from the the linear map due to 64k round-up. And
> > > a page fault happens when trying to access the ACPI_RECLAIM_MEMORY:
> > >
> > >     [...] Unable to handle kernel paging request at virtual address ffff0000dfd80000
> > >
> > > To fix this, add ACPI_MEMORY_NVS into the linear map.
> > >
> > > Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
> > > Cc: stable@vger.kernel.org # 5.15+
> >
> > What commit id does this fix?  Can you include that as well?
> >
>
> It should be 7aff79e297ee ("Drivers: hv: Enable Hyper-V code to be built
> on ARM64"), but as Ard mentioned earlier, this could be fixed at the VM
> firmware, and Oliver is working on that. Should the situation change, I
> will send a V2 with more information and include the commit id.
>

The patch as-is is not acceptable to me, so no need to send a v2 just
to add more information.

Please consider the fix I proposed for arch_memremap_can_ram_remap()
if fixing this in the firmware is not feasible.