Re: [XEN v3 03/12] xen/Arm: vreg: Support vreg_reg64_* helpers on AArch32

From: Michal Orzel <michal.orzel@amd.com>
To: Ayan Kumar Halder <ayan.kumar.halder@amd.com>,
	<xen-devel@lists.xenproject.org>
Cc: <sstabellini@kernel.org>, <stefanos@xilinx.com>, <julien@xen.org>,
	<Volodymyr_Babchuk@epam.com>, <bertrand.marquis@arm.com>,
	<jgrall@amazon.com>, <burzalodowa@gmail.com>
Subject: Re: [XEN v3 03/12] xen/Arm: vreg: Support vreg_reg64_* helpers on AArch32
Date: Thu, 17 Nov 2022 14:11:30 +0100	[thread overview]
Message-ID: <a2a471dc-f757-940b-c0bb-2eba696e5a70@amd.com> (raw)
In-Reply-To: <20221111141739.2872-4-ayan.kumar.halder@amd.com>

Hi Ayan,

On 11/11/2022 15:17, Ayan Kumar Halder wrote:
> In some situations (e.g. GICR_TYPER), the hypervior may need to emulate
> 64bit registers in AArch32 mode. In such situations, the hypervisor may
> need to read/modify the lower or upper 32 bits of the 64 bit register.
> 
> In AArch32, 'unsigned long' is 32 bits. Thus, we cannot use it for 64 bit
> registers.
> 
> While we could replace 'unsigned long' by 'uint64_t', it is not entirely clear
> whether a 32-bit compiler would not allocate register for the upper 32-bit.
> Therefore fold vreg_reg_* helper in the size specific one and use the
> appropriate type based on the size requested.
> 
> Signed-off-by: Ayan Kumar Halder <ayan.kumar.halder@amd.com>
Reviewed-by: Michal Orzel <michal.orzel@amd.com>

~Michal