linux-kernel - Re: Qemu Guest kernel 4.20-rc1 PCIe hotplug issue

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Date:   Tue, 13 Nov 2018 14:59:10 +0200
From:   "mika.westerberg@...ux.intel.com" <mika.westerberg@...ux.intel.com>
To:     Shameerali Kolothum Thodi <shameerali.kolothum.thodi@...wei.com>
Cc:     "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Wangzhou (B)" <wangzhou1@...ilicon.com>,
        Linuxarm <linuxarm@...wei.com>, Lukas Wunner <lukas@...ner.de>
Subject: Re: Qemu Guest kernel 4.20-rc1 PCIe hotplug issue

On Tue, Nov 13, 2018 at 12:36:20PM +0000, Shameerali Kolothum Thodi wrote:
> > @@ -156,9 +156,9 @@ static void pcie_do_write_cmd(struct controller *ctrl,
> > u16 cmd,
> >  	slot_ctrl |= (cmd & mask);
> >  	ctrl->cmd_busy = 1;
> >  	smp_mb();
> > +	ctrl->slot_ctrl = slot_ctrl;
> 
> Actually I tried this one, but it doesn't help in this case as the initial 
> pcie_capability_read_word() returns the slot_ctrl without PCI_EXP_SLTCTL_HPIE
> bit set.  It looks to me  pcie_enable_notification() function enables this,
> 
> 	if (!pciehp_poll_mode)
> 		cmd |= PCI_EXP_SLTCTL_HPIE | PCI_EXP_SLTCTL_CCIE;
> 
> I don't know this is as per the spec or not as the initial cap read doesn't seems to
> have the PCI_EXP_SLTCTL_HPIE bit set.

If I read the code right cmd value should end up in ctrl->slot_ctrl
properly from pcie_enable_notification().

However, I think we are missing check for PCI_EXP_SLTCTL_CCIE in
pciehp_isr().

Here's an updated patch, can you try and see if it makes any difference?

diff --git a/drivers/pci/hotplug/pciehp_hpc.c b/drivers/pci/hotplug/pciehp_hpc.c
index 7dd443aea5a5..da2cbe892444 100644
--- a/drivers/pci/hotplug/pciehp_hpc.c
+++ b/drivers/pci/hotplug/pciehp_hpc.c
@@ -156,9 +156,9 @@ static void pcie_do_write_cmd(struct controller *ctrl, u16 cmd,
 	slot_ctrl |= (cmd & mask);
 	ctrl->cmd_busy = 1;
 	smp_mb();
+	ctrl->slot_ctrl = slot_ctrl;
 	pcie_capability_write_word(pdev, PCI_EXP_SLTCTL, slot_ctrl);
 	ctrl->cmd_started = jiffies;
-	ctrl->slot_ctrl = slot_ctrl;
 
 	/*
 	 * Controllers with the Intel CF118 and similar errata advertise
@@ -522,7 +522,7 @@ static irqreturn_t pciehp_isr(int irq, void *dev_id)
 	 * in the Slot Control register (PCIe r4.0, sec 6.7.3.4).
 	 */
 	if (pdev->current_state == PCI_D3cold ||
-	    (!(ctrl->slot_ctrl & PCI_EXP_SLTCTL_HPIE) && !pciehp_poll_mode))
+	    (!(ctrl->slot_ctrl & (PCI_EXP_SLTCTL_HPIE | PCI_EXP_SLTCTL_CCIE)) && !pciehp_poll_mode))
 		return IRQ_NONE;
 
 	/*