linux-kernel - Re: [PATCH v3 1/2] PCI: hv: Replace hv_vp_set with hv

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Date:   Wed, 27 Feb 2019 16:53:37 +0100
From:   Vitaly Kuznetsov <vkuznets@...hat.com>
To:     Maya Nakamura <m.maya.nakamura@...il.com>
Cc:     lorenzo.pieralisi@....com, bhelgaas@...gle.com,
        linux-pci@...r.kernel.org, kys@...rosoft.com,
        sthemmin@...rosoft.com, olaf@...fle.de, apw@...onical.com,
        jasowang@...hat.com, mikelley@...rosoft.com,
        Alexander.Levin@...rosoft.com, linux-kernel@...r.kernel.org,
        driverdev-devel@...uxdriverproject.org, haiyangz@...rosoft.com,
        marcelo.cerri@...onical.com
Subject: Re: [PATCH v3 1/2] PCI: hv: Replace hv_vp_set with hv_vpset

Maya Nakamura <m.maya.nakamura@...il.com> writes:

> Remove a duplicate definition of VP set (hv_vp_set) and use the common
> definition (hv_vpset) that is used in other places.
>
> Change the order of the members in struct hv_pcibus_device so that the
> declaration of retarget_msi_interrupt_params is the last member. Struct
> hv_vpset, which contains a flexible array, is nested two levels deep in
> struct hv_pcibus_device via retarget_msi_interrupt_params.
>
> Add a comment that retarget_msi_interrupt_params should be the last member
> of struct hv_pcibus_device.
>
> Signed-off-by: Maya Nakamura <m.maya.nakamura@...il.com>
> ---
> Change in v3:
> - Correct the v2 change log.
>
> Change in v2:
> - Update the commit message.
>
>  drivers/pci/controller/pci-hyperv.c | 25 ++++++++++++-------------
>  1 file changed, 12 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/pci/controller/pci-hyperv.c b/drivers/pci/controller/pci-hyperv.c
> index 9ba4d12c179c..da8b58d8630d 100644
> --- a/drivers/pci/controller/pci-hyperv.c
> +++ b/drivers/pci/controller/pci-hyperv.c
> @@ -393,12 +393,6 @@ struct hv_interrupt_entry {
>  
>  #define HV_VP_SET_BANK_COUNT_MAX	5 /* current implementation limit */
>  
> -struct hv_vp_set {
> -	u64	format;			/* 0 (HvGenericSetSparse4k) */
> -	u64	valid_banks;
> -	u64	masks[HV_VP_SET_BANK_COUNT_MAX];
> -};
> -
>  /*
>   * flags for hv_device_interrupt_target.flags
>   */
> @@ -410,7 +404,7 @@ struct hv_device_interrupt_target {
>  	u32	flags;
>  	union {
>  		u64		 vp_mask;
> -		struct hv_vp_set vp_set;
> +		struct hv_vpset vp_set;
>  	};
>  };
>  
> @@ -460,12 +454,16 @@ struct hv_pcibus_device {
>  	struct msi_controller msi_chip;
>  	struct irq_domain *irq_domain;
>  
> -	/* hypercall arg, must not cross page boundary */
> -	struct retarget_msi_interrupt retarget_msi_interrupt_params;
> -
>  	spinlock_t retarget_msi_interrupt_lock;
>  
>  	struct workqueue_struct *wq;
> +
> +	/* hypercall arg, must not cross page boundary */
> +	struct retarget_msi_interrupt retarget_msi_interrupt_params;
> +

One more thing here (and again sorry for being late): this structure is
being used as Hyper-V hypercall argument and these have special
requirements on alignment (8 bytes). struct retarget_msi_interrupt is
packed and depending on your environment/compiler you may or may not see
the issue but I has able to get HVCALL_RETARGET_INTERRUPT failing with
the return value of 4 (HV_STATUS_INVALID_ALIGNMENT).

I suggest we add __aligned(8) to 'struct retarget_msi_interrupt'
definition (I haven't tested this but should work). This is not a new
issue, it existed before your patch, but the code movement you do may
change the exposure.


> +	/*
> +	 * Don't put anything here: retarget_msi_interrupt_params must be last
> +	 */
>  };
>  
>  /*
> @@ -955,12 +953,13 @@ static void hv_irq_unmask(struct irq_data *data)
>  		 */
>  		params->int_target.flags |=
>  			HV_DEVICE_INTERRUPT_TARGET_PROCESSOR_SET;
> -		params->int_target.vp_set.valid_banks =
> +		params->int_target.vp_set.valid_bank_mask =
>  			(1ull << HV_VP_SET_BANK_COUNT_MAX) - 1;
>  
>  		/*
>  		 * var-sized hypercall, var-size starts after vp_mask (thus
> -		 * vp_set.format does not count, but vp_set.valid_banks does).
> +		 * vp_set.format does not count, but vp_set.valid_bank_mask
> +		 * does).
>  		 */
>  		var_size = 1 + HV_VP_SET_BANK_COUNT_MAX;
>  
> @@ -974,7 +973,7 @@ static void hv_irq_unmask(struct irq_data *data)
>  				goto exit_unlock;
>  			}
>  
> -			params->int_target.vp_set.masks[cpu_vmbus / 64] |=
> +			params->int_target.vp_set.bank_contents[cpu_vmbus / 64]	|=
>  				(1ULL << (cpu_vmbus & 63));
>  		}
>  	} else {

-- 
Vitaly