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

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Message-ID: <20190227164220.GA20672@e107981-ln.cambridge.arm.com>
Date:   Wed, 27 Feb 2019 16:42:20 +0000
From:   Lorenzo Pieralisi <lorenzo.pieralisi@....com>
To:     Vitaly Kuznetsov <vkuznets@...hat.com>,
        Maya Nakamura <m.maya.nakamura@...il.com>
Cc:     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

On Wed, Feb 27, 2019 at 04:53:37PM +0100, Vitaly Kuznetsov wrote:
> 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.

I am happy to apply this small fix _before_ this patch but if you want
me to merge them for v5.1 this must be put together and tested quite
quickly.

For the time being I am not dropping this patch from the PCI queue,
waiting for an update from you guys.

Thanks,
Lorenzo

> 
> 
> > +	/*
> > +	 * 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