linux-kernel - [PATCH v1 1/6] powerpc/code-patching: Use pte_offset_kernel() instead of virt_to

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Date:   Tue, 27 Sep 2022 16:33:03 +0200
From:   Christophe Leroy <christophe.leroy@...roup.eu>
To:     Benjamin Gray <bgray@...ux.ibm.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Nicholas Piggin <npiggin@...il.com>
Cc:     Christophe Leroy <christophe.leroy@...roup.eu>,
        linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: [PATCH v1 1/6] powerpc/code-patching: Use pte_offset_kernel() instead of virt_to_kpte()

virt_to_kpte() checks pmd_none() and returns NULL in that case.

__do_patch_instruction() doesn't expect the pmd to be none and
doesn't handle the case anyway.

So avoid the pmd_none() check by using pte_offset_kernel()
directly.

It improves ftrace activation by approx 1% on an 8xx.

Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>
---
 arch/powerpc/lib/code-patching.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/powerpc/lib/code-patching.c b/arch/powerpc/lib/code-patching.c
index ad0cf3108dd0..0f3acb0534b6 100644
--- a/arch/powerpc/lib/code-patching.c
+++ b/arch/powerpc/lib/code-patching.c
@@ -158,7 +158,7 @@ static int __do_patch_instruction(u32 *addr, ppc_inst_t instr)
 	text_poke_addr = (unsigned long)__this_cpu_read(text_poke_area)->addr & PAGE_MASK;
 	patch_addr = (u32 *)(text_poke_addr + offset_in_page(addr));
 
-	pte = virt_to_kpte(text_poke_addr);
+	pte = pte_offset_kernel(pmd_off_k(text_poke_addr), text_poke_addr);
 	__set_pte_at(&init_mm, text_poke_addr, pte, pfn_pte(pfn, PAGE_KERNEL), 0);
 	/* See ptesync comment in radix__set_pte_at() */
 	if (radix_enabled())
-- 
2.37.1