Re: [PATCH v2 3/3] PCI: hv: Introduce hv_msi_entry

From: Andrew Murray <amurray@thegoodpenguin.co.uk>
To: Boqun Feng <boqun.feng@gmail.com>
Cc: linux-pci@vger.kernel.org, linux-hyperv@vger.kernel.org,
	linux-kernel@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	Michael Kelley <mikelley@microsoft.com>,
	"K. Y. Srinivasan" <kys@microsoft.com>,
	Haiyang Zhang <haiyangz@microsoft.com>,
	Stephen Hemminger <sthemmin@microsoft.com>,
	Sasha Levin <sashal@kernel.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
	"H. Peter Anvin" <hpa@zytor.com>,
	x86@kernel.org, Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>,
	Andrew Murray <andrew.murray@arm.com>,
	Bjorn Helgaas <bhelgaas@google.com>
Subject: Re: [PATCH v2 3/3] PCI: hv: Introduce hv_msi_entry
Date: Mon, 3 Feb 2020 09:51:40 +0000	[thread overview]
Message-ID: <20200203095140.GE20189@big-machine> (raw)
In-Reply-To: <20200203050313.69247-4-boqun.feng@gmail.com>

On Mon, Feb 03, 2020 at 01:03:13PM +0800, Boqun Feng wrote:
> Add a new structure (hv_msi_entry), which is also defined int tlfs, to

s/int/in the/ ?

> describe the msi entry for HVCALL_RETARGET_INTERRUPT. The structure is
> needed because its layout may be different from architecture to
> architecture.
> 
> Also add a new generic interface hv_set_msi_address_from_desc() to allow
> different archs to set the msi address from msi_desc.
> 
> No functional change, only preparation for the future support of virtual
> PCI on non-x86 architectures.
> 
> Signed-off-by: Boqun Feng (Microsoft) <boqun.feng@gmail.com>
> ---
>  arch/x86/include/asm/hyperv-tlfs.h  | 11 +++++++++--
>  arch/x86/include/asm/mshyperv.h     |  5 +++++
>  drivers/pci/controller/pci-hyperv.c |  4 ++--
>  3 files changed, 16 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/x86/include/asm/hyperv-tlfs.h b/arch/x86/include/asm/hyperv-tlfs.h
> index 4a76e442481a..953b3ad38746 100644
> --- a/arch/x86/include/asm/hyperv-tlfs.h
> +++ b/arch/x86/include/asm/hyperv-tlfs.h
> @@ -912,11 +912,18 @@ struct hv_partition_assist_pg {
>  	u32 tlb_lock_count;
>  };
>  
> +union hv_msi_entry {
> +	u64 as_uint64;
> +	struct {
> +		u32 address;
> +		u32 data;
> +	} __packed;
> +};
> +
>  struct hv_interrupt_entry {
>  	u32 source;			/* 1 for MSI(-X) */
>  	u32 reserved1;
> -	u32 address;
> -	u32 data;
> +	union hv_msi_entry msi_entry;
>  } __packed;
>  
>  /*
> diff --git a/arch/x86/include/asm/mshyperv.h b/arch/x86/include/asm/mshyperv.h
> index 6b79515abb82..3bdaa3b6e68f 100644
> --- a/arch/x86/include/asm/mshyperv.h
> +++ b/arch/x86/include/asm/mshyperv.h
> @@ -240,6 +240,11 @@ bool hv_vcpu_is_preempted(int vcpu);
>  static inline void hv_apic_init(void) {}
>  #endif
>  
> +#define hv_set_msi_address_from_desc(msi_entry, msi_desc)	\
> +do {								\
> +	(msi_entry)->address = (msi_desc)->msg.address_lo;	\
> +} while (0)

Given that this is a single statement, is there really a need for the do ; while(0) ?

> +
>  #else /* CONFIG_HYPERV */
>  static inline void hyperv_init(void) {}
>  static inline void hyperv_setup_mmu_ops(void) {}
> diff --git a/drivers/pci/controller/pci-hyperv.c b/drivers/pci/controller/pci-hyperv.c
> index 0d9b74503577..2240f2b3643e 100644
> --- a/drivers/pci/controller/pci-hyperv.c
> +++ b/drivers/pci/controller/pci-hyperv.c
> @@ -1170,8 +1170,8 @@ static void hv_irq_unmask(struct irq_data *data)
>  	memset(params, 0, sizeof(*params));
>  	params->partition_id = HV_PARTITION_ID_SELF;
>  	params->int_entry.source = 1; /* MSI(-X) */
> -	params->int_entry.address = msi_desc->msg.address_lo;
> -	params->int_entry.data = msi_desc->msg.data;
> +	hv_set_msi_address_from_desc(&params->int_entry.msi_entry, msi_desc);
> +	params->int_entry.msi_entry.data = msi_desc->msg.data;

If the layout may differ, then don't we also need a wrapper for data?

Thanks,

Andrew Murray

>  	params->device_id = (hbus->hdev->dev_instance.b[5] << 24) |
>  			   (hbus->hdev->dev_instance.b[4] << 16) |
>  			   (hbus->hdev->dev_instance.b[7] << 8) |
> -- 
> 2.24.1
> 