kho: allow scratch areas with zero size

Patch series "kho: fixes and cleanups", v3.

These are small KHO and KHO test fixes and cleanups.

This patch (of 3):

Parsing of kho_scratch parameter treats zero size as an invalid value,
although it should be fine for user to request zero sized scratch area for
some types if scratch memory, when for example there is no need to create
scratch area in the low memory.

Treat zero as a valid value for a scratch area size but reject kho_scratch
parameter that defines no scratch memory at all.

Link: https://lkml.kernel.org/r/20250811082510.4154080-1-rppt@kernel.org
Link: https://lkml.kernel.org/r/20250811082510.4154080-2-rppt@kernel.org
Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Reviewed-by: Pratyush Yadav <pratyush@kernel.org>
Cc: Alexander Graf <graf@amazon.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: Changyuan Lyu <changyuanl@google.com>
Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Thomas Weißschuh <linux@weissschuh.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/kernel/kexec_handover.c b/kernel/kexec_handover.c
index ecd1ac210dbd74edc83f9cd4c5d4483e14399222..1a65419e37560fd4253be27d3d61fb38c7b0dfa3 100644 (file)
--- a/kernel/kexec_handover.c
+++ b/kernel/kexec_handover.c
@@ -405,6 +405,7 @@ static int __init kho_parse_scratch_size(char *p)
 {
        size_t len;
        unsigned long sizes[3];
+       size_t total_size = 0;
        int i;
 
        if (!p)
@@ -441,11 +442,15 @@ static int __init kho_parse_scratch_size(char *p)
                }
 
                sizes[i] = memparse(p, &endp);
-               if (!sizes[i] || endp == p)
+               if (endp == p)
                        return -EINVAL;
                p = endp;
+               total_size += sizes[i];
        }
 
+       if (!total_size)
+               return -EINVAL;
+
        scratch_size_lowmem = sizes[0];
        scratch_size_global = sizes[1];
        scratch_size_pernode = sizes[2];