* [PATCH v2] platform: generic: Keep some empty space in FDT passed to next stage
@ 2025-12-01 5:00 Anup Patel
2025-12-07 10:59 ` Samuel Holland
0 siblings, 1 reply; 5+ messages in thread
From: Anup Patel @ 2025-12-01 5:00 UTC (permalink / raw)
To: Atish Patra; +Cc: Andrew Jones, Anup Patel, opensbi, Anup Patel
Leaving no empty space in the FDT passed to the next booting stage
causes the following U-Boot crash on Ventana internal platforms:
Unhandled exception: Load access fault
EPC: 00000000fffa6372 RA: 00000000fffa7418 TVAL: 0001746174730068
EPC: 0000000080245372 RA: 0000000080246418 reloc adjusted
SP: 00000000fef38440 GP: 00000000fef40e60 TP: 0000000000000000
T0: 00000000fef40a70 T1: 000000000000ff00 T2: 0000000000000000
S0: 00000000fffc17a8 S1: 00000000fef38d40 A0: 7375746174730068
A1: 00000000fffc17a8 A2: 0000000000000010 A3: 0000000000000010
A4: 0000000000000000 A5: 00000000fffc17b8 A6: 0000000000ff0000
A7: 000000000000b100 S2: 0000000000000000 S3: 0000000000000001
S4: 00000000fef38d40 S5: 7375746174730068 S6: 0000000000000000
S7: 00000000fef4eef0 S8: 00000000fef4ef90 S9: 0000000000000000
S10: 0000000000000000 S11: 00000000fef4efc0 T3: 00000000fef40ea8
T4: 0000000000ff0000 T5: 00000000fef40a60 T6: 00000000fef40a6c
To address the above issue, keep some minimal empty space in the
FDT instead of no empty space.
Fixes: bbe9a23060e9 ("platform: generic: Pack the FDT after applying fixups")
Signed-off-by: Anup Patel <apatel@ventanamicro.com>
---
Changes since v1:
- Add Kconfig option for amount of empty space in FDT with default
value as 4KB
---
platform/generic/Kconfig | 5 +++++
platform/generic/platform.c | 3 +++
2 files changed, 8 insertions(+)
diff --git a/platform/generic/Kconfig b/platform/generic/Kconfig
index 25b8886b..b1808012 100644
--- a/platform/generic/Kconfig
+++ b/platform/generic/Kconfig
@@ -23,6 +23,11 @@ config PLATFORM_GENERIC_MINOR_VER
range 0 65535
default 1
+config PLATFORM_GENERIC_FDT_EMPTY_SPACE
+ int "Platform FDT empty space (KB)"
+ range 0 1024
+ default 4
+
config PLATFORM_ALLWINNER_D1
bool "Allwinner D1 support"
depends on FDT_IRQCHIP_PLIC
diff --git a/platform/generic/platform.c b/platform/generic/platform.c
index e66f99fa..ddfc9e80 100644
--- a/platform/generic/platform.c
+++ b/platform/generic/platform.c
@@ -245,7 +245,10 @@ int generic_final_init(bool cold_boot)
fdt_fixups(fdt);
fdt_domain_fixup(fdt);
+ /* Minimize the empty space in FDT to 4KB */
fdt_pack(fdt);
+ fdt_open_into(fdt, fdt, fdt_totalsize(fdt) +
+ CONFIG_PLATFORM_GENERIC_FDT_EMPTY_SPACE * 1024);
return 0;
}
--
2.43.0
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^ permalink raw reply related [flat|nested] 5+ messages in thread
* Re: [PATCH v2] platform: generic: Keep some empty space in FDT passed to next stage
2025-12-01 5:00 [PATCH v2] platform: generic: Keep some empty space in FDT passed to next stage Anup Patel
@ 2025-12-07 10:59 ` Samuel Holland
2025-12-07 14:53 ` Anup Patel
0 siblings, 1 reply; 5+ messages in thread
From: Samuel Holland @ 2025-12-07 10:59 UTC (permalink / raw)
To: Anup Patel, Atish Patra; +Cc: Andrew Jones, Anup Patel, opensbi
Hi Anup,
On 2025-11-30 11:00 PM, Anup Patel wrote:
> Leaving no empty space in the FDT passed to the next booting stage
> causes the following U-Boot crash on Ventana internal platforms:
>
> Unhandled exception: Load access fault
> EPC: 00000000fffa6372 RA: 00000000fffa7418 TVAL: 0001746174730068
> EPC: 0000000080245372 RA: 0000000080246418 reloc adjusted
>
> SP: 00000000fef38440 GP: 00000000fef40e60 TP: 0000000000000000
> T0: 00000000fef40a70 T1: 000000000000ff00 T2: 0000000000000000
> S0: 00000000fffc17a8 S1: 00000000fef38d40 A0: 7375746174730068
> A1: 00000000fffc17a8 A2: 0000000000000010 A3: 0000000000000010
> A4: 0000000000000000 A5: 00000000fffc17b8 A6: 0000000000ff0000
> A7: 000000000000b100 S2: 0000000000000000 S3: 0000000000000001
> S4: 00000000fef38d40 S5: 7375746174730068 S6: 0000000000000000
> S7: 00000000fef4eef0 S8: 00000000fef4ef90 S9: 0000000000000000
> S10: 0000000000000000 S11: 00000000fef4efc0 T3: 00000000fef40ea8
> T4: 0000000000ff0000 T5: 00000000fef40a60 T6: 00000000fef40a6c
>
> To address the above issue, keep some minimal empty space in the
> FDT instead of no empty space.
>
> Fixes: bbe9a23060e9 ("platform: generic: Pack the FDT after applying fixups")
> Signed-off-by: Anup Patel <apatel@ventanamicro.com>
> ---
> Changes since v1:
> - Add Kconfig option for amount of empty space in FDT with default
> value as 4KB
> ---
> platform/generic/Kconfig | 5 +++++
> platform/generic/platform.c | 3 +++
> 2 files changed, 8 insertions(+)
>
> diff --git a/platform/generic/Kconfig b/platform/generic/Kconfig
> index 25b8886b..b1808012 100644
> --- a/platform/generic/Kconfig
> +++ b/platform/generic/Kconfig
> @@ -23,6 +23,11 @@ config PLATFORM_GENERIC_MINOR_VER
> range 0 65535
> default 1
>
> +config PLATFORM_GENERIC_FDT_EMPTY_SPACE
> + int "Platform FDT empty space (KB)"
> + range 0 1024
> + default 4
Since this is a workaround for a specific platform, and the workaround should
eventually be obsoleted by a U-Boot fix, please default this to zero.
> +
> config PLATFORM_ALLWINNER_D1
> bool "Allwinner D1 support"
> depends on FDT_IRQCHIP_PLIC
> diff --git a/platform/generic/platform.c b/platform/generic/platform.c
> index e66f99fa..ddfc9e80 100644
> --- a/platform/generic/platform.c
> +++ b/platform/generic/platform.c
> @@ -245,7 +245,10 @@ int generic_final_init(bool cold_boot)
> fdt_fixups(fdt);
> fdt_domain_fixup(fdt);
>
> + /* Minimize the empty space in FDT to 4KB */
This comment is no longer accurate, since the padding is not a fixed size.
> fdt_pack(fdt);
> + fdt_open_into(fdt, fdt, fdt_totalsize(fdt) +
> + CONFIG_PLATFORM_GENERIC_FDT_EMPTY_SPACE * 1024);
This change reintroduces the problem that motivated adding fdt_pack().
fdt_open_into() does not initialize the unused space, so once again the range
[fdt, fdt + fdt_totalsize(fdt)) contains unitialized data.
If having unitialized data in the FDT blob is not a problem on the platform
requiring this workaround, then I suppose the code is fine. Otherwise, this
would need a memset().
Regards,
Samuel
>
> return 0;
> }
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^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH v2] platform: generic: Keep some empty space in FDT passed to next stage
2025-12-07 10:59 ` Samuel Holland
@ 2025-12-07 14:53 ` Anup Patel
2025-12-09 6:32 ` Samuel Holland
0 siblings, 1 reply; 5+ messages in thread
From: Anup Patel @ 2025-12-07 14:53 UTC (permalink / raw)
To: Samuel Holland; +Cc: Anup Patel, Atish Patra, Andrew Jones, opensbi
On Sun, Dec 7, 2025 at 4:29 PM Samuel Holland <samuel.holland@sifive.com> wrote:
>
> Hi Anup,
>
> On 2025-11-30 11:00 PM, Anup Patel wrote:
> > Leaving no empty space in the FDT passed to the next booting stage
> > causes the following U-Boot crash on Ventana internal platforms:
> >
> > Unhandled exception: Load access fault
> > EPC: 00000000fffa6372 RA: 00000000fffa7418 TVAL: 0001746174730068
> > EPC: 0000000080245372 RA: 0000000080246418 reloc adjusted
> >
> > SP: 00000000fef38440 GP: 00000000fef40e60 TP: 0000000000000000
> > T0: 00000000fef40a70 T1: 000000000000ff00 T2: 0000000000000000
> > S0: 00000000fffc17a8 S1: 00000000fef38d40 A0: 7375746174730068
> > A1: 00000000fffc17a8 A2: 0000000000000010 A3: 0000000000000010
> > A4: 0000000000000000 A5: 00000000fffc17b8 A6: 0000000000ff0000
> > A7: 000000000000b100 S2: 0000000000000000 S3: 0000000000000001
> > S4: 00000000fef38d40 S5: 7375746174730068 S6: 0000000000000000
> > S7: 00000000fef4eef0 S8: 00000000fef4ef90 S9: 0000000000000000
> > S10: 0000000000000000 S11: 00000000fef4efc0 T3: 00000000fef40ea8
> > T4: 0000000000ff0000 T5: 00000000fef40a60 T6: 00000000fef40a6c
> >
> > To address the above issue, keep some minimal empty space in the
> > FDT instead of no empty space.
> >
> > Fixes: bbe9a23060e9 ("platform: generic: Pack the FDT after applying fixups")
> > Signed-off-by: Anup Patel <apatel@ventanamicro.com>
> > ---
> > Changes since v1:
> > - Add Kconfig option for amount of empty space in FDT with default
> > value as 4KB
> > ---
> > platform/generic/Kconfig | 5 +++++
> > platform/generic/platform.c | 3 +++
> > 2 files changed, 8 insertions(+)
> >
> > diff --git a/platform/generic/Kconfig b/platform/generic/Kconfig
> > index 25b8886b..b1808012 100644
> > --- a/platform/generic/Kconfig
> > +++ b/platform/generic/Kconfig
> > @@ -23,6 +23,11 @@ config PLATFORM_GENERIC_MINOR_VER
> > range 0 65535
> > default 1
> >
> > +config PLATFORM_GENERIC_FDT_EMPTY_SPACE
> > + int "Platform FDT empty space (KB)"
> > + range 0 1024
> > + default 4
>
> Since this is a workaround for a specific platform, and the workaround should
> eventually be obsoleted by a U-Boot fix, please default this to zero.
Although the issue manifests on Ventana internal platforms,
the issue is not Ventana specific and can happen on any platform
where U-Boot tries to modify FDT passed by OpenSBI without
adding extra space.
>
> > +
> > config PLATFORM_ALLWINNER_D1
> > bool "Allwinner D1 support"
> > depends on FDT_IRQCHIP_PLIC
> > diff --git a/platform/generic/platform.c b/platform/generic/platform.c
> > index e66f99fa..ddfc9e80 100644
> > --- a/platform/generic/platform.c
> > +++ b/platform/generic/platform.c
> > @@ -245,7 +245,10 @@ int generic_final_init(bool cold_boot)
> > fdt_fixups(fdt);
> > fdt_domain_fixup(fdt);
> >
> > + /* Minimize the empty space in FDT to 4KB */
>
> This comment is no longer accurate, since the padding is not a fixed size.
Sure, I will update.
>
> > fdt_pack(fdt);
> > + fdt_open_into(fdt, fdt, fdt_totalsize(fdt) +
> > + CONFIG_PLATFORM_GENERIC_FDT_EMPTY_SPACE * 1024);
>
> This change reintroduces the problem that motivated adding fdt_pack().
> fdt_open_into() does not initialize the unused space, so once again the range
> [fdt, fdt + fdt_totalsize(fdt)) contains unitialized data.
>
> If having unitialized data in the FDT blob is not a problem on the platform
> requiring this workaround, then I suppose the code is fine. Otherwise, this
> would need a memset().
I think it is better to do memset() on additional space in fdt_open_into()
itself but that would be a separate change in libfdt.
Regards,
Anup
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^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH v2] platform: generic: Keep some empty space in FDT passed to next stage
2025-12-07 14:53 ` Anup Patel
@ 2025-12-09 6:32 ` Samuel Holland
2025-12-09 6:44 ` Anup Patel
0 siblings, 1 reply; 5+ messages in thread
From: Samuel Holland @ 2025-12-09 6:32 UTC (permalink / raw)
To: Anup Patel; +Cc: Anup Patel, Atish Patra, Andrew Jones, opensbi
Hi Anup,
On 2025-12-07 11:53 PM, Anup Patel wrote:
> On Sun, Dec 7, 2025 at 4:29 PM Samuel Holland <samuel.holland@sifive.com> wrote:
>> On 2025-11-30 11:00 PM, Anup Patel wrote:
>>> Leaving no empty space in the FDT passed to the next booting stage
>>> causes the following U-Boot crash on Ventana internal platforms:
>>>
>>> Unhandled exception: Load access fault
>>> EPC: 00000000fffa6372 RA: 00000000fffa7418 TVAL: 0001746174730068
>>> EPC: 0000000080245372 RA: 0000000080246418 reloc adjusted
>>>
>>> SP: 00000000fef38440 GP: 00000000fef40e60 TP: 0000000000000000
>>> T0: 00000000fef40a70 T1: 000000000000ff00 T2: 0000000000000000
>>> S0: 00000000fffc17a8 S1: 00000000fef38d40 A0: 7375746174730068
>>> A1: 00000000fffc17a8 A2: 0000000000000010 A3: 0000000000000010
>>> A4: 0000000000000000 A5: 00000000fffc17b8 A6: 0000000000ff0000
>>> A7: 000000000000b100 S2: 0000000000000000 S3: 0000000000000001
>>> S4: 00000000fef38d40 S5: 7375746174730068 S6: 0000000000000000
>>> S7: 00000000fef4eef0 S8: 00000000fef4ef90 S9: 0000000000000000
>>> S10: 0000000000000000 S11: 00000000fef4efc0 T3: 00000000fef40ea8
>>> T4: 0000000000ff0000 T5: 00000000fef40a60 T6: 00000000fef40a6c
>>>
>>> To address the above issue, keep some minimal empty space in the
>>> FDT instead of no empty space.
>>>
>>> Fixes: bbe9a23060e9 ("platform: generic: Pack the FDT after applying fixups")
>>> Signed-off-by: Anup Patel <apatel@ventanamicro.com>
>>> ---
>>> Changes since v1:
>>> - Add Kconfig option for amount of empty space in FDT with default
>>> value as 4KB
>>> ---
>>> platform/generic/Kconfig | 5 +++++
>>> platform/generic/platform.c | 3 +++
>>> 2 files changed, 8 insertions(+)
>>>
>>> diff --git a/platform/generic/Kconfig b/platform/generic/Kconfig
>>> index 25b8886b..b1808012 100644
>>> --- a/platform/generic/Kconfig
>>> +++ b/platform/generic/Kconfig
>>> @@ -23,6 +23,11 @@ config PLATFORM_GENERIC_MINOR_VER
>>> range 0 65535
>>> default 1
>>>
>>> +config PLATFORM_GENERIC_FDT_EMPTY_SPACE
>>> + int "Platform FDT empty space (KB)"
>>> + range 0 1024
>>> + default 4
>>
>> Since this is a workaround for a specific platform, and the workaround should
>> eventually be obsoleted by a U-Boot fix, please default this to zero.
>
> Although the issue manifests on Ventana internal platforms,
> the issue is not Ventana specific and can happen on any platform
> where U-Boot tries to modify FDT passed by OpenSBI without
> adding extra space.
It's still a U-Boot bug, no? Is your plan to keep the workaround indefinitely?
>>> +
>>> config PLATFORM_ALLWINNER_D1
>>> bool "Allwinner D1 support"
>>> depends on FDT_IRQCHIP_PLIC
>>> diff --git a/platform/generic/platform.c b/platform/generic/platform.c
>>> index e66f99fa..ddfc9e80 100644
>>> --- a/platform/generic/platform.c
>>> +++ b/platform/generic/platform.c
>>> @@ -245,7 +245,10 @@ int generic_final_init(bool cold_boot)
>>> fdt_fixups(fdt);
>>> fdt_domain_fixup(fdt);
>>>
>>> + /* Minimize the empty space in FDT to 4KB */
>>
>> This comment is no longer accurate, since the padding is not a fixed size.
>
> Sure, I will update.
>
>>
>>> fdt_pack(fdt);
>>> + fdt_open_into(fdt, fdt, fdt_totalsize(fdt) +
>>> + CONFIG_PLATFORM_GENERIC_FDT_EMPTY_SPACE * 1024);
>>
>> This change reintroduces the problem that motivated adding fdt_pack().
>> fdt_open_into() does not initialize the unused space, so once again the range
>> [fdt, fdt + fdt_totalsize(fdt)) contains unitialized data.
>>
>> If having unitialized data in the FDT blob is not a problem on the platform
>> requiring this workaround, then I suppose the code is fine. Otherwise, this
>> would need a memset().
>
> I think it is better to do memset() on additional space in fdt_open_into()
> itself but that would be a separate change in libfdt.
I don't have an opinion on whether it is better to change libfdt, but we need to
add the memset() in at least one place to avoid regressing here.
Regards,
Samuel
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^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH v2] platform: generic: Keep some empty space in FDT passed to next stage
2025-12-09 6:32 ` Samuel Holland
@ 2025-12-09 6:44 ` Anup Patel
0 siblings, 0 replies; 5+ messages in thread
From: Anup Patel @ 2025-12-09 6:44 UTC (permalink / raw)
To: Samuel Holland; +Cc: Anup Patel, Atish Patra, Andrew Jones, opensbi
On Tue, Dec 9, 2025 at 12:03 PM Samuel Holland
<samuel.holland@sifive.com> wrote:
>
> Hi Anup,
>
> On 2025-12-07 11:53 PM, Anup Patel wrote:
> > On Sun, Dec 7, 2025 at 4:29 PM Samuel Holland <samuel.holland@sifive.com> wrote:
> >> On 2025-11-30 11:00 PM, Anup Patel wrote:
> >>> Leaving no empty space in the FDT passed to the next booting stage
> >>> causes the following U-Boot crash on Ventana internal platforms:
> >>>
> >>> Unhandled exception: Load access fault
> >>> EPC: 00000000fffa6372 RA: 00000000fffa7418 TVAL: 0001746174730068
> >>> EPC: 0000000080245372 RA: 0000000080246418 reloc adjusted
> >>>
> >>> SP: 00000000fef38440 GP: 00000000fef40e60 TP: 0000000000000000
> >>> T0: 00000000fef40a70 T1: 000000000000ff00 T2: 0000000000000000
> >>> S0: 00000000fffc17a8 S1: 00000000fef38d40 A0: 7375746174730068
> >>> A1: 00000000fffc17a8 A2: 0000000000000010 A3: 0000000000000010
> >>> A4: 0000000000000000 A5: 00000000fffc17b8 A6: 0000000000ff0000
> >>> A7: 000000000000b100 S2: 0000000000000000 S3: 0000000000000001
> >>> S4: 00000000fef38d40 S5: 7375746174730068 S6: 0000000000000000
> >>> S7: 00000000fef4eef0 S8: 00000000fef4ef90 S9: 0000000000000000
> >>> S10: 0000000000000000 S11: 00000000fef4efc0 T3: 00000000fef40ea8
> >>> T4: 0000000000ff0000 T5: 00000000fef40a60 T6: 00000000fef40a6c
> >>>
> >>> To address the above issue, keep some minimal empty space in the
> >>> FDT instead of no empty space.
> >>>
> >>> Fixes: bbe9a23060e9 ("platform: generic: Pack the FDT after applying fixups")
> >>> Signed-off-by: Anup Patel <apatel@ventanamicro.com>
> >>> ---
> >>> Changes since v1:
> >>> - Add Kconfig option for amount of empty space in FDT with default
> >>> value as 4KB
> >>> ---
> >>> platform/generic/Kconfig | 5 +++++
> >>> platform/generic/platform.c | 3 +++
> >>> 2 files changed, 8 insertions(+)
> >>>
> >>> diff --git a/platform/generic/Kconfig b/platform/generic/Kconfig
> >>> index 25b8886b..b1808012 100644
> >>> --- a/platform/generic/Kconfig
> >>> +++ b/platform/generic/Kconfig
> >>> @@ -23,6 +23,11 @@ config PLATFORM_GENERIC_MINOR_VER
> >>> range 0 65535
> >>> default 1
> >>>
> >>> +config PLATFORM_GENERIC_FDT_EMPTY_SPACE
> >>> + int "Platform FDT empty space (KB)"
> >>> + range 0 1024
> >>> + default 4
> >>
> >> Since this is a workaround for a specific platform, and the workaround should
> >> eventually be obsoleted by a U-Boot fix, please default this to zero.
> >
> > Although the issue manifests on Ventana internal platforms,
> > the issue is not Ventana specific and can happen on any platform
> > where U-Boot tries to modify FDT passed by OpenSBI without
> > adding extra space.
>
> It's still a U-Boot bug, no? Is your plan to keep the workaround indefinitely?
It is certainly a U-Boot bug. We will keep the workaround for atleast
6 months (one OpenSBI release) after U-Boot has fixed it.
>
> >>> +
> >>> config PLATFORM_ALLWINNER_D1
> >>> bool "Allwinner D1 support"
> >>> depends on FDT_IRQCHIP_PLIC
> >>> diff --git a/platform/generic/platform.c b/platform/generic/platform.c
> >>> index e66f99fa..ddfc9e80 100644
> >>> --- a/platform/generic/platform.c
> >>> +++ b/platform/generic/platform.c
> >>> @@ -245,7 +245,10 @@ int generic_final_init(bool cold_boot)
> >>> fdt_fixups(fdt);
> >>> fdt_domain_fixup(fdt);
> >>>
> >>> + /* Minimize the empty space in FDT to 4KB */
> >>
> >> This comment is no longer accurate, since the padding is not a fixed size.
> >
> > Sure, I will update.
> >
> >>
> >>> fdt_pack(fdt);
> >>> + fdt_open_into(fdt, fdt, fdt_totalsize(fdt) +
> >>> + CONFIG_PLATFORM_GENERIC_FDT_EMPTY_SPACE * 1024);
> >>
> >> This change reintroduces the problem that motivated adding fdt_pack().
> >> fdt_open_into() does not initialize the unused space, so once again the range
> >> [fdt, fdt + fdt_totalsize(fdt)) contains unitialized data.
> >>
> >> If having unitialized data in the FDT blob is not a problem on the platform
> >> requiring this workaround, then I suppose the code is fine. Otherwise, this
> >> would need a memset().
> >
> > I think it is better to do memset() on additional space in fdt_open_into()
> > itself but that would be a separate change in libfdt.
>
> I don't have an opinion on whether it is better to change libfdt, but we need to
> add the memset() in at least one place to avoid regressing here.
>
Understood. My suggestion is to do it as a separate patch irrespective
of where we do it.
Regards,
Anup
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2025-12-01 5:00 [PATCH v2] platform: generic: Keep some empty space in FDT passed to next stage Anup Patel
2025-12-07 10:59 ` Samuel Holland
2025-12-07 14:53 ` Anup Patel
2025-12-09 6:32 ` Samuel Holland
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