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Re: Need guidance to support reading GICR_TYPER (64 bit register) on Aarch32_v8r
- To: Julien Grall <julien@xxxxxxx>, "Stabellini, Stefano" <stefano.stabellini@xxxxxxx>, bertrand Marquis <Bertrand.Marquis@xxxxxxx>, "Volodymyr_Babchuk@xxxxxxxx" <Volodymyr_Babchuk@xxxxxxxx>, Henry Wang <Henry.Wang@xxxxxxx>, Penny Zheng <Penny.Zheng@xxxxxxx>
- From: Ayan Kumar Halder <ayankuma@xxxxxxx>
- Date: Thu, 13 Oct 2022 15:30:31 +0100
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- Cc: Jaxson Han <jaxson.han@xxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- Delivery-date: Thu, 13 Oct 2022 14:30:51 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 13/10/2022 14:20, Julien Grall wrote:
On 13/10/2022 12:47, Ayan Kumar Halder wrote:
Hi Arm mantainers/Folks,
Hello,
Hi Julien,
Appreciate your help as always. :)
Please refer to the discussion
https://github.com/zephyrproject-rtos/zephyr/pull/51163 .
We intend to run Zephyr as a domU guest on Xen on Aarch32_v8R fixed
virtual platform.
Zephyr is trying to read GICR_TYPER which is a 64 bit register using
ldrd instruction.
As GICR is emulated by Xen, so this instruction gets trapped with HSR
= 0x9200000c.
As ISV is 0, so Xen cannot emulate this instruction.
The proposed solution is to use two sys_read32() on GICR_TYPER to
return the lower and upper 32 bits.
With this, HSR = 0x9383 000c, ISV=1 so ISS is valid.
Now, for Xen to emulate this read, I have proposed the modifications
(in my last comment).
I am confused. Looking at the emulation of GICR_TYPER in Xen
(arch/arm/vgic-v3.c), the code should already be able to handle 32-bit
access.
When I compile Xen for arm32, vreg_reg64_extract() definitions do not exist.
The reason being
https://xenbits.xen.org/gitweb/?p=xen.git;a=blob;f=xen/arch/arm/include/asm/vreg.h;h=f26a70d024e2d1f933ea66793ea6e42f81c7a8cf;hb=9029bc265cdf2bd63376dde9fdd91db4ce9c0586#l189
, BITS_PER_LONG is 32 (Refer xen/arch/arm/include/asm/config.h).
.Thus, the guest need to invoke sys_read32() twice (GICR_TYPER and
GICR_TYPER+4).
I doesn't look like we need to modify Xen. What did I miss?
Cheers,
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