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From: Anup Patel <apatel@ventanamicro.com>
To: Palmer Dabbelt <palmer@dabbelt.com>,
	Paul Walmsley <paul.walmsley@sifive.com>
Cc: =?UTF-8?q?Bj=C3=B6rn=20T=C3=B6pel?= <bjorn@kernel.org>,
	Atish Patra <atishp@atishpatra.org>,
	Andrew Jones <ajones@ventanamicro.com>,
	Sunil V L <sunilvl@ventanamicro.com>,
	Anup Patel <anup@brainfault.org>,
	linux-riscv@lists.infradead.org,
	linux-kernel@vger.kernel.org,
	Anup Patel <apatel@ventanamicro.com>
Subject: [PATCH] RISC-V: Don't use IPIs in flush_icache_all() when patching text
Date: Mon,  5 Feb 2024 09:59:55 +0530
Message-Id: <20240205042955.833752-1-apatel@ventanamicro.com>
Precedence: bulk
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit

If some of the HARTs are parked by stop machine then IPI-based
flushing in flush_icache_all() will hang. This hang is observed
when text patching is invoked by various debug and BPF features.

To avoid this hang, we force use of SBI-based icache flushing
when patching text.

Fixes: 627922843235 ("RISC-V: Use IPIs for remote icache flush when possible")
Reported-by: Bjorn Topel <bjorn@kernel.org>
Closes: https://gist.github.com/bjoto/04a580568378f3b5483af07cd9d22501
Signed-off-by: Anup Patel <apatel@ventanamicro.com>
---
 arch/riscv/include/asm/cacheflush.h | 7 ++++---
 arch/riscv/kernel/hibernate.c       | 2 +-
 arch/riscv/kernel/patch.c           | 4 ++--
 arch/riscv/mm/cacheflush.c          | 7 ++++---
 4 files changed, 11 insertions(+), 9 deletions(-)

diff --git a/arch/riscv/include/asm/cacheflush.h b/arch/riscv/include/asm/cacheflush.h
index a129dac4521d..561e079f34af 100644
--- a/arch/riscv/include/asm/cacheflush.h
+++ b/arch/riscv/include/asm/cacheflush.h
@@ -32,7 +32,8 @@ static inline void flush_dcache_page(struct page *page)
  * RISC-V doesn't have an instruction to flush parts of the instruction cache,
  * so instead we just flush the whole thing.
  */
-#define flush_icache_range(start, end) flush_icache_all()
+#define flush_icache_range(start, end) flush_icache_all(true)
+#define flush_icache_patch_range(start, end) flush_icache_all(false)
 #define flush_icache_user_page(vma, pg, addr, len) \
 	flush_icache_mm(vma->vm_mm, 0)
 
@@ -43,12 +44,12 @@ static inline void flush_dcache_page(struct page *page)
 
 #ifndef CONFIG_SMP
 
-#define flush_icache_all() local_flush_icache_all()
+#define flush_icache_all(want_ipi) local_flush_icache_all()
 #define flush_icache_mm(mm, local) flush_icache_all()
 
 #else /* CONFIG_SMP */
 
-void flush_icache_all(void);
+void flush_icache_all(bool want_ipi);
 void flush_icache_mm(struct mm_struct *mm, bool local);
 
 #endif /* CONFIG_SMP */
diff --git a/arch/riscv/kernel/hibernate.c b/arch/riscv/kernel/hibernate.c
index 671b686c0158..388f10e187ba 100644
--- a/arch/riscv/kernel/hibernate.c
+++ b/arch/riscv/kernel/hibernate.c
@@ -153,7 +153,7 @@ int swsusp_arch_suspend(void)
 	} else {
 		suspend_restore_csrs(hibernate_cpu_context);
 		flush_tlb_all();
-		flush_icache_all();
+		flush_icache_all(true);
 
 		/*
 		 * Tell the hibernation core that we've just restored the memory.
diff --git a/arch/riscv/kernel/patch.c b/arch/riscv/kernel/patch.c
index 37e87fdcf6a0..721e144a7847 100644
--- a/arch/riscv/kernel/patch.c
+++ b/arch/riscv/kernel/patch.c
@@ -182,7 +182,7 @@ int patch_text_set_nosync(void *addr, u8 c, size_t len)
 	ret = patch_insn_set(tp, c, len);
 
 	if (!ret)
-		flush_icache_range((uintptr_t)tp, (uintptr_t)tp + len);
+		flush_icache_patch_range((uintptr_t)tp, (uintptr_t)tp + len);
 
 	return ret;
 }
@@ -217,7 +217,7 @@ int patch_text_nosync(void *addr, const void *insns, size_t len)
 	ret = patch_insn_write(tp, insns, len);
 
 	if (!ret)
-		flush_icache_range((uintptr_t) tp, (uintptr_t) tp + len);
+		flush_icache_patch_range((uintptr_t) tp, (uintptr_t) tp + len);
 
 	return ret;
 }
diff --git a/arch/riscv/mm/cacheflush.c b/arch/riscv/mm/cacheflush.c
index 55a34f2020a8..03cd3d4831ef 100644
--- a/arch/riscv/mm/cacheflush.c
+++ b/arch/riscv/mm/cacheflush.c
@@ -17,11 +17,12 @@ static void ipi_remote_fence_i(void *info)
 	return local_flush_icache_all();
 }
 
-void flush_icache_all(void)
+void flush_icache_all(bool want_ipi)
 {
 	local_flush_icache_all();
 
-	if (IS_ENABLED(CONFIG_RISCV_SBI) && !riscv_use_ipi_for_rfence())
+	if (IS_ENABLED(CONFIG_RISCV_SBI) &&
+	    (!want_ipi || !riscv_use_ipi_for_rfence()))
 		sbi_remote_fence_i(NULL);
 	else
 		on_each_cpu(ipi_remote_fence_i, NULL, 1);
@@ -87,7 +88,7 @@ void flush_icache_pte(pte_t pte)
 	struct folio *folio = page_folio(pte_page(pte));
 
 	if (!test_bit(PG_dcache_clean, &folio->flags)) {
-		flush_icache_all();
+		flush_icache_all(true);
 		set_bit(PG_dcache_clean, &folio->flags);
 	}
 }
-- 
2.34.1