linux-kernel - Re: [PATCH RFC v2 08/11] scsi: ufs: core: Perform read back after disabling interrupts

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <20231227061317.GF2814@thinkpad>
Date: Wed, 27 Dec 2023 11:43:17 +0530
From: Manivannan Sadhasivam <mani@...nel.org>
To: Andrew Halaney <ahalaney@...hat.com>
Cc: Andy Gross <agross@...nel.org>, Bjorn Andersson <andersson@...nel.org>,
	Konrad Dybcio <konrad.dybcio@...aro.org>,
	"James E.J. Bottomley" <jejb@...ux.ibm.com>,
	"Martin K. Petersen" <martin.petersen@...cle.com>,
	Yaniv Gardi <ygardi@...eaurora.org>,
	Dov Levenglick <dovl@...eaurora.org>,
	Hannes Reinecke <hare@...e.de>,
	Subhash Jadavani <subhashj@...eaurora.org>,
	Gilad Broner <gbroner@...eaurora.org>,
	Venkat Gopalakrishnan <venkatg@...eaurora.org>,
	Janek Kotas <jank@...ence.com>,
	Alim Akhtar <alim.akhtar@...sung.com>,
	Avri Altman <avri.altman@....com>,
	Bart Van Assche <bvanassche@....org>,
	Anjana Hari <quic_ahari@...cinc.com>,
	Dolev Raviv <draviv@...eaurora.org>,
	Can Guo <quic_cang@...cinc.com>, Will Deacon <will@...nel.org>,
	linux-arm-msm@...r.kernel.org, linux-scsi@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH RFC v2 08/11] scsi: ufs: core: Perform read back after
 disabling interrupts

On Thu, Dec 21, 2023 at 12:25:25PM -0600, Andrew Halaney wrote:
> Currently, interrupts are cleared and disabled prior to registering the
> interrupt. An mb() is used to complete the clear/disable writes before
> the interrupt is registered.
> 
> mb() ensure that the write completes, but completion doesn't mean that
> it isn't stored in a buffer somewhere. The recommendation for
> ensuring these bits have taken effect on the device is to perform a read
> back to force it to make it all the way to the device. This is
> documented in device-io.rst and a talk by Will Deacon on this can
> be seen over here:
> 
>     https://youtu.be/i6DayghhA8Q?si=MiyxB5cKJXSaoc01&t=1678
> 
> Let's do that to ensure these bits hit the device. Because the mb()'s
> purpose wasn't to add extra ordering (on top of the ordering guaranteed
> by writel()/readl()), it can safely be removed.
> 
> Fixes: 199ef13cac7d ("scsi: ufs: avoid spurious UFS host controller interrupts")
> Signed-off-by: Andrew Halaney <ahalaney@...hat.com>

Same comment as patch 07/11.

Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>

- Mani

> ---
>  drivers/ufs/core/ufshcd.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/ufs/core/ufshcd.c b/drivers/ufs/core/ufshcd.c
> index 7bfb556e5b8e..bb603769b029 100644
> --- a/drivers/ufs/core/ufshcd.c
> +++ b/drivers/ufs/core/ufshcd.c
> @@ -10568,7 +10568,7 @@ int ufshcd_init(struct ufs_hba *hba, void __iomem *mmio_base, unsigned int irq)
>  	 * Make sure that UFS interrupts are disabled and any pending interrupt
>  	 * status is cleared before registering UFS interrupt handler.
>  	 */
> -	mb();
> +	ufshcd_readl(hba, REG_INTERRUPT_ENABLE);
>  
>  	/* IRQ registration */
>  	err = devm_request_irq(dev, irq, ufshcd_intr, IRQF_SHARED, UFSHCD, hba);
> 
> -- 
> 2.43.0
> 

-- 
மணிவண்ணன் சதாசிவம்