On 09/11/2022 06:46, Wei Chen wrote:
Hi Julien,
Hi Wei,
-----Original Message-----
From: Julien Grall <[email protected]>
Sent: 2022年11月7日 3:45
To: Wei Chen <[email protected]>; [email protected]
Cc: nd <[email protected]>; Stefano Stabellini <[email protected]>; Bertrand
Marquis <[email protected]>; Volodymyr Babchuk
<[email protected]>
Subject: Re: [PATCH v6 07/11] xen/arm: implement FIXMAP_ADDR for MPU
systems
Hi Wei,
On 04/11/2022 10:07, Wei Chen wrote:
FIXMAP is a special virtual address section for Xen to map some
physical ram or device memory temporarily in initialization for
MMU systems. FIXMAP_ADDR will return a virtual address by index
for special purpose phys-to-virt mapping usage. For example,
FIXMAP_ADDR(FIXMAP_CONSOLE) for early console mapping and
FIXMAP_ADDR(FIXMAP_MISC) for copy_from_paddr.
To me, we are bending quite a bit the definition of the fixmap. There
are not many use of the FIXMAP within the code and I think it would
simply be better to abstract the use (or removing it when possible) and
avoid defining FIXMAP_ADDR() & co for MPU.
I agree, if we don't mind to add some CONFIG_HAS_MPU in some generic code.
FAOD, this is not what I had in mind. Instead, it was to provide helper
which for !HAS_MPU would call fixmap and for HAS_MPU would do the work
to map the region in the MPU.
[...]
xen/arch/arm/Kconfig | 2 +-
xen/arch/arm/include/asm/config_mpu.h | 2 ++
xen/arch/arm/include/asm/fixmap.h | 25 +++++++++++++++++++++++++
3 files changed, 28 insertions(+), 1 deletion(-)
diff --git a/xen/arch/arm/Kconfig b/xen/arch/arm/Kconfig
index ac276307d6..1458ffa777 100644
--- a/xen/arch/arm/Kconfig
+++ b/xen/arch/arm/Kconfig
@@ -16,7 +16,7 @@ config ARM
select HAS_DEVICE_TREE
select HAS_PASSTHROUGH
select HAS_PDX
- select HAS_PMAP
+ select HAS_PMAP if !HAS_MPU
I can't find any change of mm.c in this series. So surely this will
break the build?
Yes, in our internal testing, open PMAP for MPU will cause building
failed, except we add some new stubs for MPU system.
Do you mean you added some stubs for PMAP? If so, I would not expect any
caller for the pmap() to be used for the MPU. Therefore, why would they
be necessary?
Cheers,
--
Julien Grall
