linux-kernel - Re: [PATCH] PCI: hv: use effective affinity mask

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Message-ID: <20171108010736.GA28427@bhelgaas-glaptop.roam.corp.google.com>
Date:   Tue, 7 Nov 2017 19:07:36 -0600
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Dexuan Cui <decui@...rosoft.com>
Cc:     Bjorn Helgaas <bhelgaas@...gle.com>,
        "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        Jake Oshins <jakeo@...rosoft.com>,
        KY Srinivasan <kys@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        "devel@...uxdriverproject.org" <devel@...uxdriverproject.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Jork Loeser <Jork.Loeser@...rosoft.com>,
        "Chris Valean (Cloudbase Solutions SRL)" <v-chvale@...rosoft.com>,
        "Adrian Suhov (Cloudbase Solutions SRL)" <v-adsuho@...rosoft.com>,
        Simon Xiao <sixiao@...rosoft.com>,
        'Eyal Mizrachi' <eyalmi@...lanox.com>,
        Jack Morgenstein <jackm@...lanox.com>,
        Armen Guezalian <armeng@...lanox.com>,
        Firas Mahameed <firas@...lanox.com>,
        Tziporet Koren <tziporet@...lanox.com>,
        Daniel Jurgens <danielj@...lanox.com>
Subject: Re: [PATCH] PCI: hv: use effective affinity mask

On Wed, Nov 01, 2017 at 08:30:53PM +0000, Dexuan Cui wrote:
> 
> The effective_affinity_mask is always set when an interrupt is assigned in
> __assign_irq_vector() -> apic->cpu_mask_to_apicid(), e.g. for struct apic
> apic_physflat: -> default_cpu_mask_to_apicid() ->
> irq_data_update_effective_affinity(), but it looks d->common->affinity
> remains all-1's before the user space or the kernel changes it later.
> 
> In the early allocation/initialization phase of an irq, we should use the
> effective_affinity_mask, otherwise Hyper-V may not deliver the interrupt
> to the expected cpu. Without the patch, if we assign 7 Mellanox ConnectX-3
> VFs to a 32-vCPU VM, one of the VFs may fail to receive interrupts.
> 
> Signed-off-by: Dexuan Cui <decui@...rosoft.com>
> Cc: Jake Oshins <jakeo@...rosoft.com>
> Cc: Jork Loeser <jloeser@...rosoft.com>
> Cc: Stephen Hemminger <sthemmin@...rosoft.com>
> Cc: K. Y. Srinivasan <kys@...rosoft.com>
> ---
> 
> Please consider this for v4.14, if it's not too late.

What would be the rationale for putting it in v4.14?  After the merge
window, I usually only merge fixes for problems introduced during the
merge window, or for serious regressions.  I can't tell if this fits
into that or not.

>  drivers/pci/host/pci-hyperv.c | 8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/pci/host/pci-hyperv.c b/drivers/pci/host/pci-hyperv.c
> index 5ccb47d..8b5f66d 100644
> --- a/drivers/pci/host/pci-hyperv.c
> +++ b/drivers/pci/host/pci-hyperv.c
> @@ -879,7 +879,7 @@ static void hv_irq_unmask(struct irq_data *data)
>  	int cpu;
>  	u64 res;
>  
> -	dest = irq_data_get_affinity_mask(data);
> +	dest = irq_data_get_effective_affinity_mask(data);
>  	pdev = msi_desc_to_pci_dev(msi_desc);
>  	pbus = pdev->bus;
>  	hbus = container_of(pbus->sysdata, struct hv_pcibus_device, sysdata);
> @@ -1042,6 +1042,7 @@ static void hv_compose_msi_msg(struct irq_data *data, struct msi_msg *msg)
>  	struct hv_pci_dev *hpdev;
>  	struct pci_bus *pbus;
>  	struct pci_dev *pdev;
> +	struct cpumask *dest;
>  	struct compose_comp_ctxt comp;
>  	struct tran_int_desc *int_desc;
>  	struct {
> @@ -1056,6 +1057,7 @@ static void hv_compose_msi_msg(struct irq_data *data, struct msi_msg *msg)
>  	int ret;
>  
>  	pdev = msi_desc_to_pci_dev(irq_data_get_msi_desc(data));
> +	dest = irq_data_get_effective_affinity_mask(data);
>  	pbus = pdev->bus;
>  	hbus = container_of(pbus->sysdata, struct hv_pcibus_device, sysdata);
>  	hpdev = get_pcichild_wslot(hbus, devfn_to_wslot(pdev->devfn));
> @@ -1081,14 +1083,14 @@ static void hv_compose_msi_msg(struct irq_data *data, struct msi_msg *msg)
>  	switch (pci_protocol_version) {
>  	case PCI_PROTOCOL_VERSION_1_1:
>  		size = hv_compose_msi_req_v1(&ctxt.int_pkts.v1,
> -					irq_data_get_affinity_mask(data),
> +					dest,
>  					hpdev->desc.win_slot.slot,
>  					cfg->vector);
>  		break;
>  
>  	case PCI_PROTOCOL_VERSION_1_2:
>  		size = hv_compose_msi_req_v2(&ctxt.int_pkts.v2,
> -					irq_data_get_affinity_mask(data),
> +					dest,
>  					hpdev->desc.win_slot.slot,
>  					cfg->vector);
>  		break;
> -- 
> 2.7.4
>