On 10/20/2025 2:27 PM, Alexander Gordeev wrote:
> On Fri, Oct 17, 2025 at 01:26:41PM +0200, Mikhail Zaslonko wrote:
>> In s390x_kvtop() early return may take place despite the verbose
>> flag. Thus we can miss page-table walk information in the vtop output
>> for kernel virtual addresses.
>> Make sure that s390x_vtop() is always called for kernel virtual addresses
>> when the verbose flag is passed to s390x_kvtop() by do_vtop().
>>
>> Suggested-by: Heiko Carstens <[email protected]>
>> Signed-off-by: Mikhail Zaslonko <[email protected]>
>> ---
>> s390x.c | 6 +++---
>> 1 file changed, 3 insertions(+), 3 deletions(-)
>>
>> diff --git a/s390x.c b/s390x.c
>> index 25dca5e..77d9082 100644
>> --- a/s390x.c
>> +++ b/s390x.c
>> @@ -943,15 +943,15 @@ s390x_kvtop(struct task_context *tc, ulong vaddr,
>> physaddr_t *paddr, int verbose
>>
>> if (!IS_KVADDR(vaddr)){
>> *paddr = 0;
>> return FALSE;
>> }
>>
>> - if (!IS_VMALLOC_ADDR(vaddr)) {
>> - *paddr = VTOP(vaddr);
>> - return TRUE;
>> + if (!verbose && !IS_VMALLOC_ADDR(vaddr)) {
>> + *paddr = VTOP(vaddr);
>> + return TRUE;
>
> Few other architectures do it like this:
>
> if (!vt->vmalloc_start) {
> *paddr = VTOP(kvaddr);
> return TRUE;
> }
> if (!IS_VMALLOC_ADDR(kvaddr)) {
> *paddr = VTOP(kvaddr);
> if (!verbose)
> return TRUE;
> }
>
> Would it work for s390x?
It would, but does it make sense updating *paddr value for non-verbose case
prior to
calling s390x_vtop() where we set it back to zero at the very start (see below).
Do you think we should just try keeping the code similar to other architectures?
/* lookup virtual address in page tables */
int s390x_vtop(ulong table, ulong vaddr, physaddr_t *phys_addr, int verbose)
{
ulong entry, paddr;
int level, len;
if (verbose)
fprintf(fp, "PAGE DIRECTORY: %016lx\n", table);
*phys_addr = 0;
>
>> }
>>
>> pgd_base = (unsigned long)vt->kernel_pgd[0];
>> return s390x_vtop(pgd_base, vaddr, paddr, verbose);
>> }
>
> Thanks!
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