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kernel-parameters: document earlycon=xenboot

PATCH In review Chris Patterson 3 participants 10 messages Apr 5, 2016 – Apr 8, 2016 Documentation

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#0 lore raw

PATCH 1/1 kernel-parameters: document earlycon=xenboot

Add earlycon=xenboot option to Documentation/kernel-parameters.txt.

---
 Documentation/kernel-parameters.txt | 2 ++
 1 file changed, 2 insertions(+)
Documentation/kernel-parameters.txt +2 -0
index ecc74fa..e01ec39 100644
@@ -1078,6 +1078,8 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
 			address. The serial port must already be setup
 			and configured. Options are not yet supported.
 
+		xenboot	Use Xen hypervisor console for early console.
+
 	earlyprintk=	[X86,SH,BLACKFIN,ARM,M68k]
 			earlyprintk=vga
 			earlyprintk=efi
Signature · 1 line
2.1.4
#1 lore raw
Quoted 2 lines · Chris Patterson

Add earlycon=xenboot option to Documentation/kernel-parameters.txt.

But it is not true.

I tried this on x86: "earlycon=xenboot console=tty0"

And nothing from Linux came during earlyboot to the Xen console?

Quoted 26 lines
---
 Documentation/kernel-parameters.txt | 2 ++
 1 file changed, 2 insertions(+)
Documentation/kernel-parameters.txt +2 -0
index ecc74fa..e01ec39 100644
@@ -1078,6 +1078,8 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
 			address. The serial port must already be setup
 			and configured. Options are not yet supported.
 
+		xenboot	Use Xen hypervisor console for early console.
+
 	earlyprintk=	[X86,SH,BLACKFIN,ARM,M68k]
 			earlyprintk=vga
 			earlyprintk=efi
Signature · 7 lines
2.1.4


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#2 lore raw
Quoted 8 lines · Konrad Rzeszutek Wilk
Quoted 2 lines · Chris Patterson

Add earlycon=xenboot option to Documentation/kernel-parameters.txt.

But it is not true.

I tried this on x86: "earlycon=xenboot console=tty0"

I can investigate further, but hopefully Stefano can chime in more definitively on what is supported.

I used "earlycon=xenboot console=hvc0" with success for dom0 on my ARM64 platform.

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#3 lore raw
In reply to Konrad Rzeszutek Wilk
Quoted 8 lines · Konrad Rzeszutek Wilk
Quoted 2 lines · Chris Patterson

Add earlycon=xenboot option to Documentation/kernel-parameters.txt.

But it is not true.

I tried this on x86: "earlycon=xenboot console=tty0"

I can investigate further, but hopefully Stefano can chime in more definitively on what is supported.

I used "earlycon=xenboot console=hvc0" with success for dom0 on my ARM64 platform.

#4 lore raw
Quoted 8 lines · Chris Patterson
Quoted 6 lines · Konrad Rzeszutek Wilk
Quoted 2 lines · Chris Patterson

Add earlycon=xenboot option to Documentation/kernel-parameters.txt.

But it is not true.

Quoted 8 lines
Quoted 2 lines

I tried this on x86: "earlycon=xenboot console=tty0"

I can investigate further, but hopefully Stefano can chime in more definitively on what is supported.

I used "earlycon=xenboot console=hvc0" with success for dom0 on my ARM64 platform.

Perhaps the documentation should also have [ARM], like some of the other ones?

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#5 lore raw
Quoted 12 lines · Konrad Rzeszutek Wilk
Quoted 11 lines · Chris Patterson
Quoted 8 lines · Konrad Rzeszutek Wilk
Quoted 2 lines · Chris Patterson

Add earlycon=xenboot option to Documentation/kernel-parameters.txt.

But it is not true.

I tried this on x86: "earlycon=xenboot console=tty0"

Quoted 8 lines
Quoted 5 lines

I can investigate further, but hopefully Stefano can chime in more definitively on what is supported.

I used "earlycon=xenboot console=hvc0" with success for dom0 on my ARM64 platform.

Perhaps the documentation should also have [ARM], like some of the other ones?

Absolutely. I will test some combinations and be explicit about what should work in v2. Thanks for the feedback.

Cheers,
-Chris

#6 lore raw
In reply to Konrad Rzeszutek Wilk
Quoted 12 lines · Konrad Rzeszutek Wilk
Quoted 11 lines · Chris Patterson
Quoted 8 lines · Konrad Rzeszutek Wilk
Quoted 2 lines · Chris Patterson

Add earlycon=xenboot option to Documentation/kernel-parameters.txt.

But it is not true.

I tried this on x86: "earlycon=xenboot console=tty0"

Quoted 8 lines
Quoted 5 lines

I can investigate further, but hopefully Stefano can chime in more definitively on what is supported.

I used "earlycon=xenboot console=hvc0" with success for dom0 on my ARM64 platform.

Perhaps the documentation should also have [ARM], like some of the other ones?

Absolutely. I will test some combinations and be explicit about what should work in v2. Thanks for the feedback.

Cheers,
-Chris

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#7 lore raw
In reply to Konrad Rzeszutek Wilk
Quoted 10 lines · Konrad Rzeszutek Wilk
Quoted 9 lines · Chris Patterson
Quoted 7 lines · Konrad Rzeszutek Wilk
Quoted 2 lines · Chris Patterson

Add earlycon=xenboot option to Documentation/kernel-parameters.txt.

But it is not true.

I tried this on x86: "earlycon=xenboot console=tty0"

Was it a PV guest? Do you have SERIAL_EARLYCON enabled in your kconfig? Does Xen allow DomU debug output via HYPERVISOR_console_io in your config?

Quoted 9 lines
Quoted 5 lines

I can investigate further, but hopefully Stefano can chime in more definitively on what is supported.

I used "earlycon=xenboot console=hvc0" with success for dom0 on my ARM64 platform.

Perhaps the documentation should also have [ARM], like some of the other ones?

I don't recall whether I actually tested earlycon on x86, but looking at the code it should work, at least for PV guests (you need to be able to issue hypercalls and HVM guests cannot do that until they map the hypercall page).

In any case given that x86 has earlyprintk, specifying xenboot as only available for ARM and ARM64 is also OK for me, but I would prefer to keep it arch-independent given that earlycon is.

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#8 lore raw
In reply to Konrad Rzeszutek Wilk
Quoted 10 lines · Konrad Rzeszutek Wilk
Quoted 9 lines · Chris Patterson
Quoted 7 lines · Konrad Rzeszutek Wilk
Quoted 2 lines · Chris Patterson

Add earlycon=xenboot option to Documentation/kernel-parameters.txt.

But it is not true.

I tried this on x86: "earlycon=xenboot console=tty0"

Was it a PV guest? Do you have SERIAL_EARLYCON enabled in your kconfig? Does Xen allow DomU debug output via HYPERVISOR_console_io in your config?

Quoted 9 lines
Quoted 5 lines

I can investigate further, but hopefully Stefano can chime in more definitively on what is supported.

I used "earlycon=xenboot console=hvc0" with success for dom0 on my ARM64 platform.

Perhaps the documentation should also have [ARM], like some of the other ones?

I don't recall whether I actually tested earlycon on x86, but looking at the code it should work, at least for PV guests (you need to be able to issue hypercalls and HVM guests cannot do that until they map the hypercall page).

In any case given that x86 has earlyprintk, specifying xenboot as only available for ARM and ARM64 is also OK for me, but I would prefer to keep it arch-independent given that earlycon is.

#9 lore raw
Quoted 5 lines · Stefano Stabellini
Quoted 4 lines · Konrad Rzeszutek Wilk
Quoted 3 lines · Chris Patterson
Quoted 1 line · Konrad Rzeszutek Wilk

On Mon, Apr 04, 2016 at 10:48:11PM -0400, Chris Patterson wrote:

Quoted 8 lines
Quoted 6 lines
Quoted 6 lines
Quoted 6 lines
Quoted 2 lines

Add earlycon=xenboot option to Documentation/kernel-parameters.txt.

But it is not true.

I tried this on x86: "earlycon=xenboot console=tty0"

Was it a PV guest? Do you have SERIAL_EARLYCON enabled in your kconfig?

Yes, dom0 in fact.

Quoted 1 line

Does Xen allow DomU debug output via HYPERVISOR_console_io in your config?

Yes. That works.

Quoted 12 lines
Quoted 11 lines
Quoted 7 lines

I can investigate further, but hopefully Stefano can chime in more definitively on what is supported.

I used "earlycon=xenboot console=hvc0" with success for dom0 on my ARM64 platform.

Perhaps the documentation should also have [ARM], like some of the other ones?

Quoted 8 lines

I don't recall whether I actually tested earlycon on x86, but looking at the code it should work, at least for PV guests (you need to be able to issue hypercalls and HVM guests cannot do that until they map the hypercall page).

In any case given that x86 has earlyprintk, specifying xenboot as only available for ARM and ARM64 is also OK for me, but I would prefer to keep it arch-independent given that earlycon is.

/me nods.

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