linux-kernel - Re: [PATCH 2/3] PCI: aardvark: Fix masking MSI interrupts

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Message-ID: <20210815173659.2mjug3jffp6a4ybg@pali>
Date:   Sun, 15 Aug 2021 19:36:59 +0200
From:   Pali Rohár <pali@...nel.org>
To:     Marc Zyngier <maz@...nel.org>
Cc:     Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Rob Herring <robh@...nel.org>,
        Krzysztof Wilczyński <kw@...ux.com>,
        Marek Behún <kabel@...nel.org>,
        linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3] PCI: aardvark: Fix masking MSI interrupts

On Sunday 15 August 2021 17:56:04 Marc Zyngier wrote:
> On Sun, 15 Aug 2021 11:36:23 +0100,
> Pali Rohár <pali@...nel.org> wrote:
> > 
> > Masking of individual MSI interrupts is done via PCIE_MSI_MASK_REG
> > register. At the driver probe time mask all MSI interrupts and then let
> > kernel IRQ chip code to unmask particular MSI interrupt when needed.
> > 
> > Signed-off-by: Pali Rohár <pali@...nel.org>
> > Cc: stable@...r.kernel.org # f21a8b1b6837 ("PCI: aardvark: Move to MSI handling using generic MSI support")
> > ---
> >  drivers/pci/controller/pci-aardvark.c | 44 ++++++++++++++++++++++++---
> >  1 file changed, 40 insertions(+), 4 deletions(-)
> > 
> > diff --git a/drivers/pci/controller/pci-aardvark.c b/drivers/pci/controller/pci-aardvark.c
> > index bacfccee44fe..96580e1e4539 100644
> > --- a/drivers/pci/controller/pci-aardvark.c
> > +++ b/drivers/pci/controller/pci-aardvark.c
> > @@ -480,12 +480,10 @@ static void advk_pcie_setup_hw(struct advk_pcie *pcie)
> >  	advk_writel(pcie, PCIE_ISR1_ALL_MASK, PCIE_ISR1_REG);
> >  	advk_writel(pcie, PCIE_IRQ_ALL_MASK, HOST_CTRL_INT_STATUS_REG);
> >  
> > -	/* Disable All ISR0/1 Sources */
> > +	/* Disable All ISR0/1 and MSI Sources */
> >  	advk_writel(pcie, PCIE_ISR0_ALL_MASK, PCIE_ISR0_MASK_REG);
> >  	advk_writel(pcie, PCIE_ISR1_ALL_MASK, PCIE_ISR1_MASK_REG);
> > -
> > -	/* Unmask all MSIs */
> > -	advk_writel(pcie, ~(u32)PCIE_MSI_ALL_MASK, PCIE_MSI_MASK_REG);
> > +	advk_writel(pcie, PCIE_MSI_ALL_MASK, PCIE_MSI_MASK_REG);
> >  
> >  	/* Unmask summary MSI interrupt */
> >  	reg = advk_readl(pcie, PCIE_ISR0_MASK_REG);
> > @@ -1026,6 +1024,40 @@ static int advk_msi_set_affinity(struct irq_data *irq_data,
> >  	return -EINVAL;
> >  }
> >  
> > +static void advk_msi_irq_mask(struct irq_data *d)
> > +{
> > +	struct advk_pcie *pcie = d->domain->host_data;
> > +	irq_hw_number_t hwirq = irqd_to_hwirq(d);
> > +	u32 mask;
> > +
> > +	mask = advk_readl(pcie, PCIE_MSI_MASK_REG);
> > +	mask |= BIT(hwirq);
> > +	advk_writel(pcie, mask, PCIE_MSI_MASK_REG);
> 
> This isn't atomic, and will results in corruption when two MSIs are
> masked/unmasked concurrently.

Does it mean that also current implementation of masking legacy
interrupt is incorrect?

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/pci/controller/pci-aardvark.c?h=v5.13#n874

> 
> 	M.
> 
> -- 
> Without deviation from the norm, progress is not possible.