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From: Nicholas Piggin <npiggin@gmail.com>
To: linuxppc-dev@lists.ozlabs.org
Cc: Nicholas Piggin <npiggin@gmail.com>
Subject: [PATCH 4/7] powerpc/security: split branch cache flush toggle from code patching
Date: Tue,  9 Jun 2020 17:06:07 +1000	[thread overview]
Message-ID: <20200609070610.846703-5-npiggin@gmail.com> (raw)
In-Reply-To: <20200609070610.846703-1-npiggin@gmail.com>

Branch cache flushing code patching has inter-dependencies on both the
link stack and the count cache flushing state.

To make the code clearer and to separate the link stack and count
cache handling, split the "toggle" (setting up variables and printing
enable/disable) from the code patching.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
---
 arch/powerpc/kernel/security.c | 94 ++++++++++++++++++----------------
 1 file changed, 51 insertions(+), 43 deletions(-)

diff --git a/arch/powerpc/kernel/security.c b/arch/powerpc/kernel/security.c
index 659ef6a92bb9..2a413af21124 100644
--- a/arch/powerpc/kernel/security.c
+++ b/arch/powerpc/kernel/security.c
@@ -427,61 +427,69 @@ static __init int stf_barrier_debugfs_init(void)
 device_initcall(stf_barrier_debugfs_init);
 #endif /* CONFIG_DEBUG_FS */
 
-static void no_count_cache_flush(void)
+static void update_branch_cache_flush(void)
 {
-	count_cache_flush_type = BRANCH_CACHE_FLUSH_NONE;
-	pr_info("count-cache-flush: flush disabled.\n");
-}
-
-static void toggle_branch_cache_flush(bool enable)
-{
-	if (!security_ftr_enabled(SEC_FTR_FLUSH_COUNT_CACHE) &&
-	    !security_ftr_enabled(SEC_FTR_FLUSH_LINK_STACK))
-		enable = false;
-
-	if (!enable) {
-		patch_instruction_site(&patch__call_flush_branch_caches,
-				       ppc_inst(PPC_INST_NOP));
 #ifdef CONFIG_KVM_BOOK3S_HV_POSSIBLE
+	// This controls the branch from guest_exit_cont to kvm_flush_link_stack
+	if (link_stack_flush_type == BRANCH_CACHE_FLUSH_NONE) {
 		patch_instruction_site(&patch__call_kvm_flush_link_stack,
 				       ppc_inst(PPC_INST_NOP));
-#endif
-		pr_info("link-stack-flush: flush disabled.\n");
-		link_stack_flush_type = BRANCH_CACHE_FLUSH_NONE;
-		no_count_cache_flush();
-		return;
+	} else {
+		patch_branch_site(&patch__call_kvm_flush_link_stack,
+				  (u64)&kvm_flush_link_stack, BRANCH_SET_LINK);
 	}
-
-	// This enables the branch from _switch to flush_branch_caches
-	patch_branch_site(&patch__call_flush_branch_caches,
-			  (u64)&flush_branch_caches, BRANCH_SET_LINK);
-
-#ifdef CONFIG_KVM_BOOK3S_HV_POSSIBLE
-	// This enables the branch from guest_exit_cont to kvm_flush_link_stack
-	patch_branch_site(&patch__call_kvm_flush_link_stack,
-			  (u64)&kvm_flush_link_stack, BRANCH_SET_LINK);
 #endif
 
-	pr_info("link-stack-flush: software flush enabled.\n");
-	link_stack_flush_type = BRANCH_CACHE_FLUSH_SW;
+	// This controls the branch from _switch to flush_branch_caches
+	if (count_cache_flush_type == BRANCH_CACHE_FLUSH_NONE &&
+	    link_stack_flush_type == BRANCH_CACHE_FLUSH_NONE) {
+		patch_instruction_site(&patch__call_flush_branch_caches,
+				       ppc_inst(PPC_INST_NOP));
+	} else {
+		patch_branch_site(&patch__call_flush_branch_caches,
+				  (u64)&flush_branch_caches, BRANCH_SET_LINK);
+
+		// If we just need to flush the link stack, early return
+		if (count_cache_flush_type == BRANCH_CACHE_FLUSH_NONE) {
+			patch_instruction_site(&patch__flush_link_stack_return,
+					       ppc_inst(PPC_INST_BLR));
+
+		// If we have flush instruction, early return
+		} else if (count_cache_flush_type == BRANCH_CACHE_FLUSH_HW) {
+			patch_instruction_site(&patch__flush_count_cache_return,
+					       ppc_inst(PPC_INST_BLR));
+		}
+	}
+}
 
-	// If we just need to flush the link stack, patch an early return
-	if (!security_ftr_enabled(SEC_FTR_FLUSH_COUNT_CACHE)) {
-		patch_instruction_site(&patch__flush_link_stack_return,
-				       ppc_inst(PPC_INST_BLR));
-		no_count_cache_flush();
-		return;
+static void toggle_branch_cache_flush(bool enable)
+{
+	if (!enable || !security_ftr_enabled(SEC_FTR_FLUSH_COUNT_CACHE)) {
+		if (count_cache_flush_type != BRANCH_CACHE_FLUSH_NONE) {
+			count_cache_flush_type = BRANCH_CACHE_FLUSH_NONE;
+			pr_info("count-cache-flush: flush disabled.\n");
+		}
+	} else {
+		if (security_ftr_enabled(SEC_FTR_BCCTR_FLUSH_ASSIST)) {
+			count_cache_flush_type = BRANCH_CACHE_FLUSH_HW;
+			pr_info("count-cache-flush: hardware flush enabled.\n");
+		} else {
+			count_cache_flush_type = BRANCH_CACHE_FLUSH_SW;
+			pr_info("count-cache-flush: software flush enabled.\n");
+		}
 	}
 
-	if (!security_ftr_enabled(SEC_FTR_BCCTR_FLUSH_ASSIST)) {
-		count_cache_flush_type = BRANCH_CACHE_FLUSH_SW;
-		pr_info("count-cache-flush: software flush enabled.\n");
-		return;
+	if (!enable || !security_ftr_enabled(SEC_FTR_FLUSH_LINK_STACK)) {
+		if (link_stack_flush_type != BRANCH_CACHE_FLUSH_NONE) {
+			link_stack_flush_type = BRANCH_CACHE_FLUSH_NONE;
+			pr_info("link-stack-flush: flush disabled.\n");
+		}
+	} else {
+		link_stack_flush_type = BRANCH_CACHE_FLUSH_SW;
+		pr_info("link-stack-flush: software flush enabled.\n");
 	}
 
-	patch_instruction_site(&patch__flush_count_cache_return, ppc_inst(PPC_INST_BLR));
-	count_cache_flush_type = BRANCH_CACHE_FLUSH_HW;
-	pr_info("count-cache-flush: hardware flush enabled.\n");
+	update_branch_cache_flush();
 }
 
 void setup_count_cache_flush(void)
-- 
2.23.0


  parent reply	other threads:[~2020-06-09  7:35 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-09  7:06 [PATCH 0/7] powerpc: branch cache flush changes Nicholas Piggin
2020-06-09  7:06 ` [PATCH 1/7] powerpc/security: re-name count cache flush to branch cache flush Nicholas Piggin
2020-06-09  7:06 ` [PATCH 2/7] powerpc/security: change link stack flush state to the flush type enum Nicholas Piggin
2020-06-09  7:06 ` [PATCH 3/7] powerpc/security: make display of branch cache flush more consistent Nicholas Piggin
2020-06-09  7:06 ` Nicholas Piggin [this message]
2020-06-09  7:06 ` [PATCH 5/7] powerpc/64s: Move branch cache flushing bcctr variant to ppc-ops.h Nicholas Piggin
2020-06-09  7:06 ` [PATCH 6/7] powerpc/security: Allow for processors that flush the link stack using the special bcctr Nicholas Piggin
2020-06-09  7:06 ` [PATCH 7/7] powerpc/64s: advertise hardware link stack flush Nicholas Piggin
2020-07-16 12:56 ` [PATCH 0/7] powerpc: branch cache flush changes Michael Ellerman
  -- strict thread matches above, loose matches on Subject: below --
2020-06-09  6:16 Nicholas Piggin
2020-06-09  6:16 ` [PATCH 4/7] powerpc/security: split branch cache flush toggle from code patching Nicholas Piggin

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