5.4-stable review patch. If anyone has any objections, please let me know.
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From: Anthony Yznaga anthony.yznaga@oracle.com
commit 6fd44a481b3c6111e4801cec964627791d0f3ec5 upstream.
An attempt to exercise sparc hugetlb code in a sun4u-based guest running under qemu results in the guest hanging due to being stuck in a trap loop. This is due to invalid hugetlb TTEs being installed that do not have the expected _PAGE_PMD_HUGE and page size bits set. Although the breakage has gone apparently unnoticed for several years, fix it now so there is the option to exercise sparc hugetlb code under qemu. This can be useful because sun4v support in qemu does not support linux guests currently and sun4v-based hardware resources may not be readily available.
Fix tested with a 6.15.2 and 6.16-rc6 kernels by running libhugetlbfs tests on a qemu guest running Debian 13.
Fixes: c7d9f77d33a7 ("sparc64: Multi-page size support") Cc: stable@vger.kernel.org Signed-off-by: Anthony Yznaga anthony.yznaga@oracle.com Tested-by: John Paul Adrian Glaubitz glaubitz@physik.fu-berlin.de Reviewed-by: John Paul Adrian Glaubitz glaubitz@physik.fu-berlin.de Reviewed-by: Andreas Larsson andreas@gaisler.com Link: https://lore.kernel.org/r/20250716012446.10357-1-anthony.yznaga@oracle.com Signed-off-by: Andreas Larsson andreas@gaisler.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/sparc/mm/hugetlbpage.c | 20 ++++++++++++++++++++ 1 file changed, 20 insertions(+)
--- a/arch/sparc/mm/hugetlbpage.c +++ b/arch/sparc/mm/hugetlbpage.c @@ -134,6 +134,26 @@ hugetlb_get_unmapped_area(struct file *f
static pte_t sun4u_hugepage_shift_to_tte(pte_t entry, unsigned int shift) { + unsigned long hugepage_size = _PAGE_SZ4MB_4U; + + pte_val(entry) = pte_val(entry) & ~_PAGE_SZALL_4U; + + switch (shift) { + case HPAGE_256MB_SHIFT: + hugepage_size = _PAGE_SZ256MB_4U; + pte_val(entry) |= _PAGE_PMD_HUGE; + break; + case HPAGE_SHIFT: + pte_val(entry) |= _PAGE_PMD_HUGE; + break; + case HPAGE_64K_SHIFT: + hugepage_size = _PAGE_SZ64K_4U; + break; + default: + WARN_ONCE(1, "unsupported hugepage shift=%u\n", shift); + } + + pte_val(entry) = pte_val(entry) | hugepage_size; return entry; }