linux-kernel - Re: [PATCH 1/1] PCI: hv: Support for create interrupt v3

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Date:   Fri, 9 Jul 2021 10:24:34 +0000
From:   Wei Liu <wei.liu@...nel.org>
To:     Sunil Muthuswamy <sunilmut@...rosoft.com>
Cc:     KY Srinivasan <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        Wei Liu <liuwe@...rosoft.com>,
        Dexuan Cui <decui@...rosoft.com>,
        Michael Kelley <mikelley@...rosoft.com>,
        "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
        "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Rob Herring <robh@...nel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Wei Liu <wei.liu@...nel.org>
Subject: Re: [PATCH 1/1] PCI: hv: Support for create interrupt v3

On Thu, Jul 08, 2021 at 11:04:49PM +0000, Sunil Muthuswamy wrote:
> Hyper-V vPCI protocol version 1_4 adds support for create interrupt
> v3. Create interrupt v3 essentially makes the size of the vector
> field bigger in the message, thereby allowing bigger vector values.
> For example, that will come into play for supporting LPI vectors
> on ARM, which start at 8192.
> 
> Signed-off-by: Sunil Muthuswamy <sunilmut@...rosoft.com>
> ---
>  drivers/pci/controller/pci-hyperv.c | 74 ++++++++++++++++++++++++++---
>  1 file changed, 68 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/pci/controller/pci-hyperv.c b/drivers/pci/controller/pci-hyperv.c
> index bebe3eeebc4e..de61b20f9604 100644
> --- a/drivers/pci/controller/pci-hyperv.c
> +++ b/drivers/pci/controller/pci-hyperv.c
> @@ -64,6 +64,7 @@ enum pci_protocol_version_t {
>  	PCI_PROTOCOL_VERSION_1_1 = PCI_MAKE_VERSION(1, 1),	/* Win10 */
>  	PCI_PROTOCOL_VERSION_1_2 = PCI_MAKE_VERSION(1, 2),	/* RS1 */
>  	PCI_PROTOCOL_VERSION_1_3 = PCI_MAKE_VERSION(1, 3),	/* Vibranium */
> +	PCI_PROTOCOL_VERSION_1_4 = PCI_MAKE_VERSION(1, 4),      /* Fe */
>  };
>  
>  #define CPU_AFFINITY_ALL	-1ULL
> @@ -73,6 +74,7 @@ enum pci_protocol_version_t {
>   * first.
>   */
>  static enum pci_protocol_version_t pci_protocol_versions[] = {
> +	PCI_PROTOCOL_VERSION_1_4,
>  	PCI_PROTOCOL_VERSION_1_3,
>  	PCI_PROTOCOL_VERSION_1_2,
>  	PCI_PROTOCOL_VERSION_1_1,
> @@ -122,6 +124,8 @@ enum pci_message_type {
>  	PCI_CREATE_INTERRUPT_MESSAGE2	= PCI_MESSAGE_BASE + 0x17,
>  	PCI_DELETE_INTERRUPT_MESSAGE2	= PCI_MESSAGE_BASE + 0x18, /* unused */
>  	PCI_BUS_RELATIONS2		= PCI_MESSAGE_BASE + 0x19,
> +	PCI_RESOURCES_ASSIGNED3         = PCI_MESSAGE_BASE + 0x1A,
> +	PCI_CREATE_INTERRUPT_MESSAGE3   = PCI_MESSAGE_BASE + 0x1B,
>  	PCI_MESSAGE_MAXIMUM
>  };
>  
> @@ -235,6 +239,21 @@ struct hv_msi_desc2 {
>  	u16	processor_array[32];
>  } __packed;
>  
> +/*
> + * struct hv_msi_desc3 - 1.3 version of hv_msi_desc
> + *	Everything is the same as in 'hv_msi_desc2' except that the size
> + *	of the 'vector_count' field is larger to support bigger vector
> + *	values. For ex: LPI vectors on ARM.
> + */
> +struct hv_msi_desc3 {
> +	u32	vector;
> +	u8	delivery_mode;
> +	u8	reserved;
> +	u16	vector_count;
> +	u16	processor_count;
> +	u16	processor_array[32];
> +} __packed;
> +
>  /**
>   * struct tran_int_desc
>   * @reserved:		unused, padding
> @@ -383,6 +402,12 @@ struct pci_create_interrupt2 {
>  	struct hv_msi_desc2 int_desc;
>  } __packed;
>  
> +struct pci_create_interrupt3 {
> +	struct pci_message message_type;
> +	union win_slot_encoding wslot;
> +	struct hv_msi_desc3 int_desc;
> +} __packed;
> +
>  struct pci_delete_interrupt {
>  	struct pci_message message_type;
>  	union win_slot_encoding wslot;
> @@ -1334,26 +1359,55 @@ static u32 hv_compose_msi_req_v1(
>  	return sizeof(*int_pkt);
>  }
>  
> +static void hv_compose_msi_req_get_cpu(struct cpumask *affinity, int *cpu,
> +				       u16 *count)

Isn't count redundant here? I don't see how this can be used safely for
passing back more than 1 cpu, since if cpu is pointing to an array, its
size is not specified.

Wei.

> +{
> +	/*
> +	 * Create MSI w/ dummy vCPU set targeting just one vCPU, overwritten
> +	 * by subsequent retarget in hv_irq_unmask().
> +	 */
> +	*cpu = cpumask_first_and(affinity, cpu_online_mask);
> +	*count = 1;
> +}
> +