From: Michael Kelley Date: Wed, 31 Dec 2025 20:14:47 +0000 (-0800) Subject: Drivers: hv: Always do Hyper-V panic notification in hv_kmsg_dump() X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=49f49d47af67f8a7b221db1d758fc634242dc91a;p=thirdparty%2Fkernel%2Flinux.git Drivers: hv: Always do Hyper-V panic notification in hv_kmsg_dump() hv_kmsg_dump() currently skips the panic notification entirely if it doesn't get any message bytes to pass to Hyper-V due to an error from kmsg_dump_get_buffer(). Skipping the notification is undesirable because it leaves the Hyper-V host uncertain about the state of a panic'ed guest. Fix this by always doing the panic notification, even if bytes_written is zero. Also ensure that bytes_written is initialized, which fixes a kernel test robot warning. The warning is actually bogus because kmsg_dump_get_buffer() happens to set bytes_written even if it fails, and in the kernel test robot's CONFIG_PRINTK not set case, hv_kmsg_dump() is never called. But do the initialization for robustness and to quiet the static checker. Fixes: 9c318a1d9b50 ("Drivers: hv: move panic report code from vmbus to hv early init code") Reported-by: kernel test robot Reported-by: Dan Carpenter Closes: https://lore.kernel.org/all/202512172103.OcUspn1Z-lkp@intel.com/ Signed-off-by: Michael Kelley Reviewed-by: Roman Kisel Signed-off-by: Wei Liu --- diff --git a/drivers/hv/hv_common.c b/drivers/hv/hv_common.c index 0a3ab7efed46..f1c17fb60dc1 100644 --- a/drivers/hv/hv_common.c +++ b/drivers/hv/hv_common.c @@ -195,13 +195,15 @@ static void hv_kmsg_dump(struct kmsg_dumper *dumper, /* * Write dump contents to the page. No need to synchronize; panic should - * be single-threaded. + * be single-threaded. Ignore failures from kmsg_dump_get_buffer() since + * panic notification should be done even if there is no message data. + * Don't assume bytes_written is set in case of failure, so initialize it. */ kmsg_dump_rewind(&iter); - kmsg_dump_get_buffer(&iter, false, hv_panic_page, HV_HYP_PAGE_SIZE, + bytes_written = 0; + (void)kmsg_dump_get_buffer(&iter, false, hv_panic_page, HV_HYP_PAGE_SIZE, &bytes_written); - if (!bytes_written) - return; + /* * P3 to contain the physical address of the panic page & P4 to * contain the size of the panic data in that page. Rest of the @@ -210,7 +212,7 @@ static void hv_kmsg_dump(struct kmsg_dumper *dumper, hv_set_msr(HV_MSR_CRASH_P0, 0); hv_set_msr(HV_MSR_CRASH_P1, 0); hv_set_msr(HV_MSR_CRASH_P2, 0); - hv_set_msr(HV_MSR_CRASH_P3, virt_to_phys(hv_panic_page)); + hv_set_msr(HV_MSR_CRASH_P3, bytes_written ? virt_to_phys(hv_panic_page) : 0); hv_set_msr(HV_MSR_CRASH_P4, bytes_written); /*