linux-kernel - Re: [PATCH v2] PCI: hv: Fix the definition of vector in hv_compose_msi

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Date:   Wed, 29 Mar 2023 18:56:12 -0700
From:   Boqun Feng <boqun.feng@...il.com>
To:     Dexuan Cui <decui@...rosoft.com>
Cc:     quic_jhugo@...cinc.com, quic_carlv@...cinc.com, wei.liu@...nel.org,
        kys@...rosoft.com, haiyangz@...rosoft.com, sthemmin@...rosoft.com,
        lpieralisi@...nel.org, bhelgaas@...gle.com,
        linux-hyperv@...r.kernel.org, linux-pci@...r.kernel.org,
        linux-kernel@...r.kernel.org, mikelley@...rosoft.com,
        robh@...nel.org, kw@...ux.com, helgaas@...nel.org,
        alex.williamson@...hat.com, stable@...r.kernel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Sasha Levin <sashal@...nel.org>
Subject: Re: [PATCH v2] PCI: hv: Fix the definition of vector in
 hv_compose_msi_msg()

[Cc stable]

On Thu, Oct 27, 2022 at 01:52:56PM -0700, Dexuan Cui wrote:
> The local variable 'vector' must be u32 rather than u8: see the
> struct hv_msi_desc3.
> 
> 'vector_count' should be u16 rather than u8: see struct hv_msi_desc,
> hv_msi_desc2 and hv_msi_desc3.
> 

Dexuan, I think this patch should only be in 5.15, because...

> Fixes: a2bad844a67b ("PCI: hv: Fix interrupt mapping for multi-MSI")

^^^ this commit is already in 5.15.y (commit id 92dcb50f7f09).

Upstream id e70af8d040d2b7904dca93d942ba23fb722e21b1
Cc: <stable@...r.kernel.org> # 5.15.x

Regards,
Boqun

> Signed-off-by: Dexuan Cui <decui@...rosoft.com>
> Cc: Jeffrey Hugo <quic_jhugo@...cinc.com>
> Cc: Carl Vanderlip <quic_carlv@...cinc.com>
> ---
> 
> v1 was posted here (sorry, I forgot to follow this up...):
> https://lwn.net/ml/linux-kernel/20220815185505.7626-1-decui@microsoft.com/
> 
> Changes in v2:
>   Added the explicit "(u8)" cast in hv_compose_msi_msg().
>   Added and improved the comments.
>   Fixed a typo in the subject in v1: s/definiton/definition
> 
>  drivers/pci/controller/pci-hyperv.c | 22 ++++++++++++++++------
>  1 file changed, 16 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/pci/controller/pci-hyperv.c b/drivers/pci/controller/pci-hyperv.c
> index e7c6f6629e7c..ba64284eaf9f 100644
> --- a/drivers/pci/controller/pci-hyperv.c
> +++ b/drivers/pci/controller/pci-hyperv.c
> @@ -1614,7 +1614,7 @@ static void hv_pci_compose_compl(void *context, struct pci_response *resp,
>  
>  static u32 hv_compose_msi_req_v1(
>  	struct pci_create_interrupt *int_pkt, const struct cpumask *affinity,
> -	u32 slot, u8 vector, u8 vector_count)
> +	u32 slot, u8 vector, u16 vector_count)
>  {
>  	int_pkt->message_type.type = PCI_CREATE_INTERRUPT_MESSAGE;
>  	int_pkt->wslot.slot = slot;
> @@ -1642,7 +1642,7 @@ static int hv_compose_msi_req_get_cpu(const struct cpumask *affinity)
>  
>  static u32 hv_compose_msi_req_v2(
>  	struct pci_create_interrupt2 *int_pkt, const struct cpumask *affinity,
> -	u32 slot, u8 vector, u8 vector_count)
> +	u32 slot, u8 vector, u16 vector_count)
>  {
>  	int cpu;
>  
> @@ -1661,7 +1661,7 @@ static u32 hv_compose_msi_req_v2(
>  
>  static u32 hv_compose_msi_req_v3(
>  	struct pci_create_interrupt3 *int_pkt, const struct cpumask *affinity,
> -	u32 slot, u32 vector, u8 vector_count)
> +	u32 slot, u32 vector, u16 vector_count)
>  {
>  	int cpu;
>  
> @@ -1701,7 +1701,12 @@ static void hv_compose_msi_msg(struct irq_data *data, struct msi_msg *msg)
>  	struct compose_comp_ctxt comp;
>  	struct tran_int_desc *int_desc;
>  	struct msi_desc *msi_desc;
> -	u8 vector, vector_count;
> +	/*
> +	 * vector_count should be u16: see hv_msi_desc, hv_msi_desc2
> +	 * and hv_msi_desc3. vector must be u32: see hv_msi_desc3.
> +	 */
> +	u16 vector_count;
> +	u32 vector;
>  	struct {
>  		struct pci_packet pci_pkt;
>  		union {
> @@ -1767,6 +1772,11 @@ static void hv_compose_msi_msg(struct irq_data *data, struct msi_msg *msg)
>  		vector_count = 1;
>  	}
>  
> +	/*
> +	 * hv_compose_msi_req_v1 and v2 are for x86 only, meaning 'vector'
> +	 * can't exceed u8. Cast 'vector' down to u8 for v1/v2 explicitly
> +	 * for better readability.
> +	 */
>  	memset(&ctxt, 0, sizeof(ctxt));
>  	init_completion(&comp.comp_pkt.host_event);
>  	ctxt.pci_pkt.completion_func = hv_pci_compose_compl;
> @@ -1777,7 +1787,7 @@ static void hv_compose_msi_msg(struct irq_data *data, struct msi_msg *msg)
>  		size = hv_compose_msi_req_v1(&ctxt.int_pkts.v1,
>  					dest,
>  					hpdev->desc.win_slot.slot,
> -					vector,
> +					(u8)vector,
>  					vector_count);
>  		break;
>  
> @@ -1786,7 +1796,7 @@ static void hv_compose_msi_msg(struct irq_data *data, struct msi_msg *msg)
>  		size = hv_compose_msi_req_v2(&ctxt.int_pkts.v2,
>  					dest,
>  					hpdev->desc.win_slot.slot,
> -					vector,
> +					(u8)vector,
>  					vector_count);
>  		break;
>  
> -- 
> 2.25.1
>