linux-kernel - Re: [PATCH v4 3/3] RISC-V: Add support for srmcfg CSR from Ssqosid ext

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Message-ID: <aOqjggmTr4ioHwB/@x1>
Date: Sat, 11 Oct 2025 11:35:46 -0700
From: Drew Fustini <fustini@...nel.org>
To: Radim Krčmář <rkrcmar@...tanamicro.com>
Cc: Paul Walmsley <paul.walmsley@...ive.com>,
	Palmer Dabbelt <palmer@...belt.com>,
	Albert Ou <aou@...s.berkeley.edu>, Alexandre Ghiti <alex@...ti.fr>,
	Conor Dooley <conor@...nel.org>, Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Kornel Dulęba <mindal@...ihalf.com>,
	Adrien Ricciardi <aricciardi@...libre.com>,
	James Morse <james.morse@....com>,
	Atish Kumar Patra <atishp@...osinc.com>,
	Atish Patra <atish.patra@...ux.dev>,
	Vasudevan Srinivasan <vasu@...osinc.com>,
	Conor Dooley <conor.dooley@...rochip.com>, guo.wenjia23@....com.cn,
	liu.qingtao2@....com.cn, linux-riscv@...ts.infradead.org,
	linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
	linux-riscv <linux-riscv-bounces@...ts.infradead.org>
Subject: Re: [PATCH v4 3/3] RISC-V: Add support for srmcfg CSR from Ssqosid
 ext

On Thu, Oct 09, 2025 at 08:47:27AM +0200, Radim Krčmář wrote:
> 2025-10-07T23:21:12-07:00, Drew Fustini <fustini@...nel.org>:
> > diff --git a/arch/riscv/include/asm/qos.h b/arch/riscv/include/asm/qos.h
> > +static inline void __switch_to_srmcfg(struct task_struct *next)
> > +{
> > +	u32 *cpu_srmcfg_ptr = this_cpu_ptr(&cpu_srmcfg);
> > +	u32 thread_srmcfg;
> > +
> > +	thread_srmcfg = READ_ONCE(next->thread.srmcfg);
> > +
> > +	if (thread_srmcfg != *cpu_srmcfg_ptr) {
> 
> Wouldn't prev->thread.srmcfg have the value of CSR_SRMCFG when executing
> switch_to?

Thanks for reviewing. Yes, you are right that prev->thread.srmcfg should
have same value as CSR_SRMCFG. Are you suggesting that the cpu_srmcfg is
not necessary as prev->thread.srmcfg should have same value?

Drew