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From:   Balbir Singh <sblbir@amazon.com>
To:     <tglx@linutronix.de>, <linux-kernel@vger.kernel.org>
CC:     <jpoimboe@redhat.com>, <tony.luck@intel.com>,
        <keescook@chromium.org>, <benh@kernel.crashing.org>,
        <x86@kernel.org>, <dave.hansen@intel.com>,
        "Balbir Singh" <sblbir@amazon.com>
Subject: [PATCH v4 4/6] arch/x86/kvm: Refactor L1D flushing
Date:   Fri, 24 Apr 2020 00:01:23 +1000
Message-ID: <20200423140125.7332-5-sblbir@amazon.com>
In-Reply-To: <20200423140125.7332-1-sblbir@amazon.com>
References: <20200423140125.7332-1-sblbir@amazon.com>
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Sender: linux-kernel-owner@vger.kernel.org
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Move out the initialization function to l1d_flush_init_once()
so that it can be reused for subsequent patches. The side-effect
of this patch is that the memory allocated for l1d flush pages
is no longer freed up and the memory allocated once is shared
amongst callers.

l1d_flush_sw/hw() are now abstracted under arch_l1d_flush().
vmx_l1d_flush_mutex however continues to exist as it also used
from other code paths.

Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Balbir Singh <sblbir@amazon.com>
---
 arch/x86/include/asm/cacheflush.h | 12 ++++---
 arch/x86/kernel/l1d_flush.c       | 53 +++++++++++++++++++++++--------
 arch/x86/kvm/vmx/vmx.c            | 20 ++----------
 3 files changed, 50 insertions(+), 35 deletions(-)

diff --git a/arch/x86/include/asm/cacheflush.h b/arch/x86/include/asm/cacheflush.h
index 21cc3b28fa63..851d8f1ab827 100644
--- a/arch/x86/include/asm/cacheflush.h
+++ b/arch/x86/include/asm/cacheflush.h
@@ -7,11 +7,13 @@
 #include <asm/special_insns.h>
 
 #define L1D_CACHE_ORDER 4
+
+enum l1d_flush_options {
+	L1D_FLUSH_POPULATE_TLB = 0x1,
+};
+
 void clflush_cache_range(void *addr, unsigned int size);
-void l1d_flush_populate_tlb(void *l1d_flush_pages);
-void *l1d_flush_alloc_pages(void);
-void l1d_flush_cleanup_pages(void *l1d_flush_pages);
-void l1d_flush_sw(void *l1d_flush_pages);
-int l1d_flush_hw(void);
+int l1d_flush_init_once(void);
+void arch_l1d_flush(enum l1d_flush_options options);
 
 #endif /* _ASM_X86_CACHEFLUSH_H */
diff --git a/arch/x86/kernel/l1d_flush.c b/arch/x86/kernel/l1d_flush.c
index 5871794f890d..a754b6c288a9 100644
--- a/arch/x86/kernel/l1d_flush.c
+++ b/arch/x86/kernel/l1d_flush.c
@@ -1,7 +1,7 @@
 #include <linux/mm.h>
 #include <asm/cacheflush.h>
 
-void *l1d_flush_alloc_pages(void)
+static void *l1d_flush_alloc_pages(void)
 {
 	struct page *page;
 	void *l1d_flush_pages = NULL;
@@ -27,20 +27,14 @@ void *l1d_flush_alloc_pages(void)
 	}
 	return l1d_flush_pages;
 }
-EXPORT_SYMBOL_GPL(l1d_flush_alloc_pages);
 
-void l1d_flush_cleanup_pages(void *l1d_flush_pages)
-{
-	free_pages((unsigned long)l1d_flush_pages, L1D_CACHE_ORDER);
-}
-EXPORT_SYMBOL_GPL(l1d_flush_cleanup_pages);
 
 /*
  * Not all users of l1d flush would want to populate the TLB first
  * split out the function so that callers can optionally flush the L1D
  * cache via sw without prefetching the TLB.
  */
-void l1d_flush_populate_tlb(void *l1d_flush_pages)
+static void l1d_flush_populate_tlb(void *l1d_flush_pages)
 {
 	int size = PAGE_SIZE << L1D_CACHE_ORDER;
 
@@ -58,9 +52,8 @@ void l1d_flush_populate_tlb(void *l1d_flush_pages)
 		    [size] "r" (size)
 		: "eax", "ebx", "ecx", "edx");
 }
-EXPORT_SYMBOL_GPL(l1d_flush_populate_tlb);
 
-int l1d_flush_hw(void)
+static int l1d_flush_hw(void)
 {
 	if (static_cpu_has(X86_FEATURE_FLUSH_L1D)) {
 		wrmsrl(MSR_IA32_FLUSH_CMD, L1D_FLUSH);
@@ -68,9 +61,8 @@ int l1d_flush_hw(void)
 	}
 	return -ENOTSUPP;
 }
-EXPORT_SYMBOL_GPL(l1d_flush_hw);
 
-void l1d_flush_sw(void *l1d_flush_pages)
+static void l1d_flush_sw(void *l1d_flush_pages)
 {
 	int size = PAGE_SIZE << L1D_CACHE_ORDER;
 
@@ -87,4 +79,39 @@ void l1d_flush_sw(void *l1d_flush_pages)
 			[size] "r" (size)
 			: "eax", "ecx");
 }
-EXPORT_SYMBOL_GPL(l1d_flush_sw);
+
+static void *l1d_flush_pages;
+static DEFINE_MUTEX(l1d_flush_mutex);
+
+/*
+ * Initialize and setup L1D flush once, each caller will reuse the
+ * l1d_flush_pages for flushing, no per CPU allocations or NUMA aware
+ * allocations at the moment.
+ */
+int l1d_flush_init_once(void)
+{
+	int ret = 0;
+
+	if (static_cpu_has(X86_FEATURE_FLUSH_L1D) || l1d_flush_pages)
+		return ret;
+
+	mutex_lock(&l1d_flush_mutex);
+	if (!l1d_flush_pages)
+		l1d_flush_pages = l1d_flush_alloc_pages();
+	ret = l1d_flush_pages ? 0 : -ENOMEM;
+	mutex_unlock(&l1d_flush_mutex);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(l1d_flush_init_once);
+
+void arch_l1d_flush(enum l1d_flush_options options)
+{
+	if (!l1d_flush_hw())
+		return;
+
+	if (options & L1D_FLUSH_POPULATE_TLB)
+		l1d_flush_populate_tlb(l1d_flush_pages);
+
+	l1d_flush_sw(l1d_flush_pages);
+}
+EXPORT_SYMBOL_GPL(arch_l1d_flush);
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 786d1615a09f..d489234c4d5a 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -203,8 +203,6 @@ static const struct {
 	[VMENTER_L1D_FLUSH_NOT_REQUIRED] = {"not required", false},
 };
 
-static void *vmx_l1d_flush_pages;
-
 static int vmx_setup_l1d_flush(enum vmx_l1d_flush_state l1tf)
 {
 	if (!boot_cpu_has_bug(X86_BUG_L1TF)) {
@@ -247,12 +245,9 @@ static int vmx_setup_l1d_flush(enum vmx_l1d_flush_state l1tf)
 		l1tf = VMENTER_L1D_FLUSH_ALWAYS;
 	}
 
-	if (l1tf != VMENTER_L1D_FLUSH_NEVER && !vmx_l1d_flush_pages &&
-	    !boot_cpu_has(X86_FEATURE_FLUSH_L1D)) {
-		vmx_l1d_flush_pages = l1d_flush_alloc_pages();
-		if (!vmx_l1d_flush_pages)
+	if (l1tf != VMENTER_L1D_FLUSH_NEVER)
+		if (l1d_flush_init_once())
 			return -ENOMEM;
-	}
 
 	l1tf_vmx_mitigation = l1tf;
 
@@ -6010,12 +6005,7 @@ static void vmx_l1d_flush(struct kvm_vcpu *vcpu)
 	}
 
 	vcpu->stat.l1d_flush++;
-
-	if (!l1d_flush_hw())
-		return;
-
-	l1d_flush_populate_tlb(vmx_l1d_flush_pages);
-	l1d_flush_sw(vmx_l1d_flush_pages);
+	arch_l1d_flush(L1D_FLUSH_POPULATE_TLB);
 }
 
 static void update_cr8_intercept(struct kvm_vcpu *vcpu, int tpr, int irr)
@@ -7983,10 +7973,6 @@ static struct kvm_x86_init_ops vmx_init_ops __initdata = {
 
 static void vmx_cleanup_l1d_flush(void)
 {
-	if (vmx_l1d_flush_pages) {
-		l1d_flush_cleanup_pages(vmx_l1d_flush_pages);
-		vmx_l1d_flush_pages = NULL;
-	}
 	/* Restore state so sysfs ignores VMX */
 	l1tf_vmx_mitigation = VMENTER_L1D_FLUSH_AUTO;
 }
-- 
2.17.1