xtensa: fix TLB sanity checker

BugLink: https://bugs.launchpad.net/bugs/1858489

commit 36de10c4 upstream.

Virtual and translated addresses retrieved by the xtensa TLB sanity
checker must be consistent, i.e. correspond to the same state of the
checked TLB entry. KASAN shadow memory is mapped dynamically using
auto-refill TLB entries and thus may change TLB state between the
virtual and translated address retrieval, resulting in false TLB
insanity report.
Move read_xtlb_translation close to read_xtlb_virtual to make sure that
read values are consistent.

Cc: stable@vger.kernel.org
Fixes: a99e07ee ("xtensa: check TLB sanity on return to userspace")
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Connor Kuehl <connor.kuehl@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

arch/xtensa/mm/tlb.c

@@ -218,6 +218,8 @@ static int check_tlb_entry(unsigned w, unsigned e, bool dtlb)
 	unsigned tlbidx = w | (e << PAGE_SHIFT);
 	unsigned r0 = dtlb ?
 		read_dtlb_virtual(tlbidx) : read_itlb_virtual(tlbidx);
+	unsigned r1 = dtlb ?
+		read_dtlb_translation(tlbidx) : read_itlb_translation(tlbidx);
 	unsigned vpn = (r0 & PAGE_MASK) | (e << PAGE_SHIFT);
 	unsigned pte = get_pte_for_vaddr(vpn);
 	unsigned mm_asid = (get_rasid_register() >> 8) & ASID_MASK;
@@ -233,8 +235,6 @@ static int check_tlb_entry(unsigned w, unsigned e, bool dtlb)
 	}
 
 	if (tlb_asid == mm_asid) {
-		unsigned r1 = dtlb ? read_dtlb_translation(tlbidx) :
-			read_itlb_translation(tlbidx);
 		if ((pte ^ r1) & PAGE_MASK) {
 			pr_err("%cTLB: way: %u, entry: %u, mapping: %08x->%08x, PTE: %08x\n",
 					dtlb ? 'D' : 'I', w, e, r0, r1, pte);