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KVM: selftests: Add helper to get host IRQ from device MSI-X for IRQ bypass test

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Introduce proc_util.c and proc_util.h to house utility functions for
interacting with the proc filesystem.

Add vfio_msix_to_host_irq(), which parses /proc/interrupts, to get the host
Linux IRQ for a given VFIO device BDF and MSI-X vector.

This helper will be used by the eventfd IRQ test to print the host IRQ
number when triggering IRQs via VFIO device, e.g. to aid in debugging if
the test fails.

Suggested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: David Matlack <dmatlack@google.com>
Co-developed-by: Josh Hilke <jrhilke@google.com>
Signed-off-by: Josh Hilke <jrhilke@google.com>
[sean: massage changelog]
Link: https://patch.msgid.link/20260626213534.3866178-9-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
This commit is contained in:
David Matlack 2026-06-26 14:35:21 -07:00 committed by Sean Christopherson
parent 3ceab37ac9
commit 362cc00162
3 changed files with 50 additions and 0 deletions
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1
tools/testing/selftests/kvm/Makefile.kvm
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@ -11,6 +11,7 @@ LIBKVM += lib/kvm_util.c
LIBKVM += lib/lru_gen_util.c
LIBKVM += lib/memstress.c
LIBKVM += lib/guest_sprintf.c
LIBKVM += lib/proc_util.c
LIBKVM += lib/rbtree.c
LIBKVM += lib/sparsebit.c
LIBKVM += lib/test_util.c

9
tools/testing/selftests/kvm/include/proc_util.h Normal file
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@ -0,0 +1,9 @@
/* SPDX-License-Identifier: GPL-2.0-only */
#ifndef SELFTEST_KVM_PROC_UTIL_H
#define SELFTEST_KVM_PROC_UTIL_H
#include <stdint.h>
unsigned int vfio_msix_to_host_irq(const char *vfio_device_bdf, int msix);
#endif /* SELFTEST_KVM_PROC_UTIL_H */

40
tools/testing/selftests/kvm/lib/proc_util.c Normal file
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@ -0,0 +1,40 @@
// SPDX-License-Identifier: GPL-2.0
#include "kvm_util.h"
#include "test_util.h"
#include "proc_util.h"
static FILE *open_proc_interrupts(void)
{
FILE *fp;
fp = fopen("/proc/interrupts", "r");
TEST_ASSERT(fp, "fopen(/proc/interrupts) failed");
return fp;
}
unsigned int vfio_msix_to_host_irq(const char *device_bdf, int msix)
{
char search_string[64];
char line[4096];
int irq = -1;
FILE *fp;
fp = open_proc_interrupts();
snprintf(search_string, sizeof(search_string), "vfio-msix[%d]", msix);
while (fgets(line, sizeof(line), fp)) {
if (strstr(line, device_bdf) && strstr(line, search_string)) {
TEST_ASSERT_EQ(1, sscanf(line, "%d:", &irq));
break;
}
}
fclose(fp);
TEST_ASSERT(irq != -1, "Failed to locate IRQ for %s %s", device_bdf,
search_string);
return (unsigned int)irq;
}