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From: Shannon Zhao <>
To: Ian Campbell <>,
	Stefano Stabellini <>,
	Shannon Zhao <>
	Christoffer Dall <>
Subject: Re: Runtime services support for Xen on ARM
Date: Tue, 10 Nov 2015 22:27:37 +0800	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

On 2015/11/10 20:36, Ian Campbell wrote:
> On Tue, 2015-11-10 at 12:26 +0000, Stefano Stabellini wrote:
>> CC'ing xen-devel and Jan
>> On Tue, 10 Nov 2015, Shannon Zhao wrote:
>>> Hi Stefano,
>>> I'm working on adding Runtime services support at Xen side. Most of
>>> work
>>> is adding the ARM part in xen/common/efi/runtime.c.
>>> There is one problem which block me. That is how to implement
>>> efi_rs_enter() and efi_rs_leave() for ARM, since I think current
>>> implementation is x86 specific and won't work on ARM. Also the
>>> rtc_lock.
>>> Could you give some suggestion? Thanks!
>> efi_rs_enter() and efi_rs_leave() look very PV x86 specific. It is
>> possible that we don't actually need to do anything at all on ARM, aside
>> from refactoring the code. Jan?
> I think these functions derive from the USE_SET_VIRTUAL_ADDRESS_MAP option.
> If that is set we call efi_rs->SetVirtualAddressMap to tell the f/w about
> our virtual address layout and can then call rs directly with no faff.
> Unfortunately SetVirtualAddressMap is incompatible with kexec (I think you
> can only call it once), so we have this USE_SET_VIRTUAL_ADDRESS_MAP option.
> Without USE_SET_VIRTUAL_ADDRESS_MAP we need to switch to a set of page
> tables which are "OK" for calling the runtime services. I'm not sure what
> "OK" means here -- but I suspect it means "1:1" in some part.
> So sadly I think we do _eventually_ need to support this mode (for kexec),
> which would mean quite a bit of refactoring (since the relevant code
> in xen/common/efi/boot.c has some x86-isms).
> But right now, since we do not yet support kexec,  I think we could get the
> ball rolling wrt RS support by setting USE_SET_VIRTUAL_ADDRESS_MAP on ARM
> and dodging the need to make efi_rs_enter() work right now. (IOW make it
> the problem of whomever wants kexec support...)
Yeah, we could set USE_SET_VIRTUAL_ADDRESS_MAP at this moment, but as 
you said, it needs to support kexec and make efi_rs_enter() work 
eventually. So if anyone know this well, please share me your ideas. 
Thanks very much.

> Unless there are issues other than kexec with SetVirtualAddressMap which
> I'm not thinking of now?
>> Similarly we don't have an rtc_lock spinlock today and it is not
>> actually needed, but for the sake of keeping the common code common, I
>> would just introduce rtc_lock on ARM too.
> Agreed.


  reply	other threads:[~2015-11-10 14:27 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <>
2015-11-10 12:26 ` Runtime services support for Xen on ARM Stefano Stabellini
2015-11-10 12:36   ` Ian Campbell
2015-11-10 14:27     ` Shannon Zhao [this message]
2015-11-12  9:06     ` Shannon Zhao
2015-11-12 11:04       ` Jan Beulich
2015-11-12 12:52         ` Shannon Zhao
2015-11-12 15:29           ` Jan Beulich
2015-11-10 13:12   ` Jan Beulich

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