Re: [RFC] efi: Add ACPI_MEMORY_NVS into the linear map

Re: [RFC] efi: Add ACPI_MEMORY_NVS into the linear map

[Boqun Feng]

(Cc the correct arm mailing list)

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+
> ---
> We hit this in an ARM64 Hyper-V VM when using 64k page size, although
> this issue may also be fixed if the efi memory regions are all 64k
> aligned, but I don't find this memory region setup is invalid per UEFI
> spec, also I don't find that spec disallows ACPI_MEMORY_NVS to be mapped
> in the OS linear map, but if there is any better way or I'm reading the
> spec incorrectly, please let me know.
> 
> It's Cced stable since 5.15 because that's when Hyper-V ARM64 support is
> added, and Hyper-V is the only one that hits the problem so far.
> 
>  drivers/firmware/efi/efi-init.c | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/firmware/efi/efi-init.c b/drivers/firmware/efi/efi-init.c
> index a00e07b853f2..9a1b9bc66d50 100644
> --- a/drivers/firmware/efi/efi-init.c
> +++ b/drivers/firmware/efi/efi-init.c
> @@ -139,6 +139,7 @@ static __init int is_usable_memory(efi_memory_desc_t *md)
>  	case EFI_LOADER_CODE:
>  	case EFI_LOADER_DATA:
>  	case EFI_ACPI_RECLAIM_MEMORY:
> +	case EFI_ACPI_MEMORY_NVS:
>  	case EFI_BOOT_SERVICES_CODE:
>  	case EFI_BOOT_SERVICES_DATA:
>  	case EFI_CONVENTIONAL_MEMORY:
> @@ -202,8 +203,12 @@ static __init void reserve_regions(void)
>  			if (!is_usable_memory(md))
>  				memblock_mark_nomap(paddr, size);
>  
> -			/* keep ACPI reclaim memory intact for kexec etc. */
> -			if (md->type == EFI_ACPI_RECLAIM_MEMORY)
> +			/*
> +			 * keep ACPI reclaim and NVS memory and intact for kexec
> +			 * etc.
> +			 */
> +			if (md->type == EFI_ACPI_RECLAIM_MEMORY ||
> +			    md->type == EFI_ACPI_MEMORY_NVS)
>  				memblock_reserve(paddr, size);
>  		}
>  	}
> -- 
> 2.43.0
> 

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Re: [RFC] efi: Add ACPI_MEMORY_NVS into the linear map

[Ard Biesheuvel]

On Fri, 16 Feb 2024 at 00:21, Ard Biesheuvel <ardb@kernel.org> wrote:
>
> (cc Oliver)
>
> On Thu, 15 Feb 2024 at 23:51, Boqun Feng <boqun.feng@gmail.com> 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|...]
> >
>
> Which memory types were listed here?
>
> > , 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
> >
>
> You trimmed all the useful information here. ACPI reclaim memory is
> reclaimable, but we don't actually do so in Linux. So this is not
> general purpose memory, it is used for a specific purpose, and the
> code that accesses it is assuming that it is accessible via the linear
> map. There are reason why this may not be the case, so the fix might
> be to use memremap() in the access instead.
>

Please try the below if the caller is already using memremap(). It
might misidentify the region because the start is in the linear map
but the end is not.


diff --git a/arch/arm64/mm/ioremap.c b/arch/arm64/mm/ioremap.c
index 269f2f63ab7d..fef0281e223c 100644
--- a/arch/arm64/mm/ioremap.c
+++ b/arch/arm64/mm/ioremap.c
@@ -31,7 +31,6 @@ void __init early_ioremap_init(void)
 bool arch_memremap_can_ram_remap(resource_size_t offset, size_t size,
                                 unsigned long flags)
 {
-       unsigned long pfn = PHYS_PFN(offset);
-
-       return pfn_is_map_memory(pfn);
+       return pfn_is_map_memory(PHYS_PFN(offset)) &&
+              pfn_is_map_memory(PHYS_PFN(offset + size - 1));
 }

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Re: [RFC] efi: Add ACPI_MEMORY_NVS into the linear map

[Boqun Feng]

On Tue, Feb 20, 2024 at 09:27:54AM +0100, Ard Biesheuvel wrote:
> 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.

Got it. Would do if necessary, thanks!

Regards,
Boqun

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