Re: [EXTERNAL] [RFC 2/3] common/cnxk: replace variable length array

Harman Kalra
2025-10-27T05:22:11Z

Hi Stephen,

Please find response inline.

Thanks
Harman

________________________________________
From: Stephen Hemminger <stephen@networkplumber.org>
Sent: Friday, October 24, 2025 01:11
To: dev@dpdk.org
Cc: Stephen Hemminger; Nithin Kumar Dabilpuram; Kiran Kumar Kokkilagadda; Sunil Kumar Kori; Satha Koteswara Rao Kottidi; Harman Kalra
Subject: [EXTERNAL] [RFC 2/3] common/cnxk: replace variable length array

This fixes errors when compiled with LTO about large VLA. .. /drivers/common/cnxk/roc_platform. c: In function ‘irq_init’: .. /drivers/common/cnxk/roc_platform. c: 92: 14: warning: argument to variable-length array is too large [-Wvla-larger-than=]
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This fixes errors when compiled with LTO about large VLA.
../drivers/common/cnxk/roc_platform.c: In function ‘irq_init’:
../drivers/common/cnxk/roc_platform.c:92:14: warning: argument to variable-length array is too large [-Wvla-larger-than=]
92 | char irq_set_buf[MSIX_IRQ_SET_BUF_LEN];
| ^

Since the number of IRQ is limited by EAL max interrupt vectors
use that define that already exists rather than a function call
hidden in a macro.

Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
---
drivers/common/cnxk/roc_platform.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/common/cnxk/roc_platform.c b/drivers/common/cnxk/roc_platform.c
index e13cb42285..1fdbf8f051 100644
--- a/drivers/common/cnxk/roc_platform.c
+++ b/drivers/common/cnxk/roc_platform.c
@@ -17,8 +17,8 @@
#include <sys/ioctl.h>
#include <unistd.h>

-#define MSIX_IRQ_SET_BUF_LEN \
- (sizeof(struct vfio_irq_set) + sizeof(int) * (plt_intr_max_intr_get(intr_handle)))
+#define MSIX_IRQ_SET_BUF_LEN \
+ (sizeof(struct vfio_irq_set) + sizeof(int) * PLT_MAX_RXTX_INTR_VEC_ID)

[HK] The value of MSIX_IRQ_SET_BUF_LEN should be derived from the maximum number of interrupts configured for a PCI device,
as obtained via plt_intr_max_intr_get(intr_handle), which internally uses the VFIO_DEVICE_GET_IRQ_INFO ioctl.
In contrast, PLT_MAX_RXTX_INTR_VEC_ID is a fixed default value representing the maximum number of interrupt vectors.
This mismatch may lead to unexpected behaviour as on certain platforms (like cnxk) where the PCI device's MSIX capability
may exceed PLT_MAX_RXTX_INTR_VEC_ID.

static int
irq_get_info(struct plt_intr_handle *intr_handle)
--
2.51.0