linux-kernel - Re: [PATCH v2 1/5] arm64/sysreg: Add HDBSS related register information

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Message-ID: <f27c6ada-7994-4ef8-a10e-27d26ed5af0f@huawei.com>
Date: Mon, 26 Jan 2026 10:21:42 +0800
From: Tian Zheng <zhengtian10@...wei.com>
To: Leonardo Bras <leo.bras@....com>, Marc Zyngier <maz@...nel.org>
CC: Tian Zheng <zhengtian10@...wei.com>, <oliver.upton@...ux.dev>,
	<catalin.marinas@....com>, <corbet@....net>, <pbonzini@...hat.com>,
	<will@...nel.org>, <linux-kernel@...r.kernel.org>, <yuzenghui@...wei.com>,
	<wangzhou1@...ilicon.com>, <yezhenyu2@...wei.com>, <xiexiangyou@...wei.com>,
	<zhengchuan@...wei.com>, <joey.gouly@....com>, <kvmarm@...ts.linux.dev>,
	<kvm@...r.kernel.org>, <linux-arm-kernel@...ts.infradead.org>,
	<linux-doc@...r.kernel.org>, <suzuki.poulose@....com>
Subject: Re: [PATCH v2 1/5] arm64/sysreg: Add HDBSS related register
 information



On 1/22/2026 11:12 PM, Leonardo Bras wrote:
> On Sat, Nov 22, 2025 at 12:40:27PM +0000, Marc Zyngier wrote:
>> On Fri, 21 Nov 2025 09:23:38 +0000,
>> Tian Zheng <zhengtian10@...wei.com> wrote:
>>>
>>> From: eillon <yezhenyu2@...wei.com>
>>>
>>> The ARM architecture added the HDBSS feature and descriptions of
>>> related registers (HDBSSBR/HDBSSPROD) in the DDI0601(ID121123) version,
>>> add them to Linux.
>>>
>>> Signed-off-by: eillon <yezhenyu2@...wei.com>
>>> Signed-off-by: Tian Zheng <zhengtian10@...wei.com>
>>> ---
>>>   arch/arm64/include/asm/esr.h     |  2 ++
>>>   arch/arm64/include/asm/kvm_arm.h |  1 +
>>>   arch/arm64/tools/sysreg          | 28 ++++++++++++++++++++++++++++
>>>   3 files changed, 31 insertions(+)
>>>
>>> diff --git a/arch/arm64/include/asm/esr.h b/arch/arm64/include/asm/esr.h
>>> index e1deed824464..a6f3cf0b9b86 100644
>>> --- a/arch/arm64/include/asm/esr.h
>>> +++ b/arch/arm64/include/asm/esr.h
>>> @@ -159,6 +159,8 @@
>>>   #define ESR_ELx_CM 		(UL(1) << ESR_ELx_CM_SHIFT)
>>>
>>>   /* ISS2 field definitions for Data Aborts */
>>> +#define ESR_ELx_HDBSSF_SHIFT	(11)
>>> +#define ESR_ELx_HDBSSF		(UL(1) << ESR_ELx_HDBSSF_SHIFT)
>>>   #define ESR_ELx_TnD_SHIFT	(10)
>>>   #define ESR_ELx_TnD 		(UL(1) << ESR_ELx_TnD_SHIFT)
>>>   #define ESR_ELx_TagAccess_SHIFT	(9)
>>> diff --git a/arch/arm64/include/asm/kvm_arm.h b/arch/arm64/include/asm/kvm_arm.h
>>> index 1da290aeedce..b71122680a03 100644
>>> --- a/arch/arm64/include/asm/kvm_arm.h
>>> +++ b/arch/arm64/include/asm/kvm_arm.h
>>> @@ -124,6 +124,7 @@
>>>   			 TCR_EL2_ORGN0_MASK | TCR_EL2_IRGN0_MASK)
>>>
>>>   /* VTCR_EL2 Registers bits */
>>> +#define VTCR_EL2_HDBSS		(1UL << 45)
>>
>> I think it is time to convert VTCR_EL2 to the sysreg infrastructure
>> instead of adding extra bits here.
> 
> 
> Hi Marc, Tian,
> 
> Marc, IIUC the above was implemented by
> https://lore.kernel.org/all/20251210173024.561160-1-maz@kernel.org
> 
> Which was recently applied to next, and it its way to mainstream.
> 
> Tian, I think it's worth rebasing this patchset on top of the above.
> 

Indeed, I've been following Marc's VTCR_EL2 patch and will rebase my
changes on top of it.

> BTW, I am working on using the feature enabled by this patchset on a new
> optimization, so please include me on any new release.

Sure, I'll make sure you're on the Cc list for the next revision.

> 
> Thanks!
> Leo
>