Received-SPF: pass (google.com: domain of linux-kernel+bounces-133678-linux.lists.archive=gmail.com@vger.kernel.org designates 2604:1380:4601:e00::3 as permitted sender) client-ip=2604:1380:4601:e00::3;
From: Jacob Pan <jacob.jun.pan@linux.intel.com>
To: LKML <linux-kernel@vger.kernel.org>,
	X86 Kernel <x86@kernel.org>,
	Peter Zijlstra <peterz@infradead.org>,
	iommu@lists.linux.dev,
	Thomas Gleixner <tglx@linutronix.de>,
	"Lu Baolu" <baolu.lu@linux.intel.com>,
	kvm@vger.kernel.org,
	Dave Hansen <dave.hansen@intel.com>,
	Joerg Roedel <joro@8bytes.org>,
	"H. Peter Anvin" <hpa@zytor.com>,
	"Borislav Petkov" <bp@alien8.de>,
	"Ingo Molnar" <mingo@redhat.com>
Cc: Paul Luse <paul.e.luse@intel.com>,
	Dan Williams <dan.j.williams@intel.com>,
	Jens Axboe <axboe@kernel.dk>,
	Raj Ashok <ashok.raj@intel.com>,
	"Tian, Kevin" <kevin.tian@intel.com>,
	maz@kernel.org,
	seanjc@google.com,
	"Robin Murphy" <robin.murphy@arm.com>,
	jim.harris@samsung.com,
	a.manzanares@samsung.com,
	"Bjorn Helgaas" <helgaas@kernel.org>,
	guang.zeng@intel.com,
	robert.hoo.linux@gmail.com,
	Jacob Pan <jacob.jun.pan@linux.intel.com>
Subject: [PATCH v2 11/13] iommu/vt-d: Make posted MSI an opt-in cmdline option
Date: Fri,  5 Apr 2024 15:31:08 -0700
Message-Id: <20240405223110.1609888-12-jacob.jun.pan@linux.intel.com>
In-Reply-To: <20240405223110.1609888-1-jacob.jun.pan@linux.intel.com>
References: <20240405223110.1609888-1-jacob.jun.pan@linux.intel.com>
Precedence: bulk
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit

Add a command line opt-in option for posted MSI if CONFIG_X86_POSTED_MSI=y.

Also introduce a helper function for testing if posted MSI is supported on
the platform.

Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
---
 Documentation/admin-guide/kernel-parameters.txt |  1 +
 arch/x86/include/asm/irq_remapping.h            | 11 +++++++++++
 drivers/iommu/irq_remapping.c                   | 13 ++++++++++++-
 3 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index bb884c14b2f6..e5fd02423c4c 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -2251,6 +2251,7 @@
 			no_x2apic_optout
 				BIOS x2APIC opt-out request will be ignored
 			nopost	disable Interrupt Posting
+			posted_msi enable MSIs delivered as posted interrupts
 
 	iomem=		Disable strict checking of access to MMIO memory
 		strict	regions from userspace.
diff --git a/arch/x86/include/asm/irq_remapping.h b/arch/x86/include/asm/irq_remapping.h
index 7a2ed154a5e1..e46bde61029b 100644
--- a/arch/x86/include/asm/irq_remapping.h
+++ b/arch/x86/include/asm/irq_remapping.h
@@ -50,6 +50,17 @@ static inline struct irq_domain *arch_get_ir_parent_domain(void)
 	return x86_vector_domain;
 }
 
+#ifdef CONFIG_X86_POSTED_MSI
+extern int enable_posted_msi;
+
+static inline bool posted_msi_supported(void)
+{
+	return enable_posted_msi && irq_remapping_cap(IRQ_POSTING_CAP);
+}
+#else
+static inline bool posted_msi_supported(void) { return false; };
+#endif
+
 #else  /* CONFIG_IRQ_REMAP */
 
 static inline bool irq_remapping_cap(enum irq_remap_cap cap) { return 0; }
diff --git a/drivers/iommu/irq_remapping.c b/drivers/iommu/irq_remapping.c
index ee59647c2050..5672783c9f1f 100644
--- a/drivers/iommu/irq_remapping.c
+++ b/drivers/iommu/irq_remapping.c
@@ -24,6 +24,10 @@ int no_x2apic_optout;
 
 int disable_irq_post = 0;
 
+#ifdef CONFIG_X86_POSTED_MSI
+int enable_posted_msi;
+#endif
+
 static int disable_irq_remap;
 static struct irq_remap_ops *remap_ops;
 
@@ -70,7 +74,14 @@ static __init int setup_irqremap(char *str)
 			no_x2apic_optout = 1;
 		else if (!strncmp(str, "nopost", 6))
 			disable_irq_post = 1;
-
+#ifdef CONFIG_X86_POSTED_MSI
+		else if (!strncmp(str, "posted_msi", 10)) {
+			if (disable_irq_post || disable_irq_remap)
+				pr_warn("Posted MSI not enabled due to conflicting options!");
+			else
+				enable_posted_msi = 1;
+		}
+#endif
 		str += strcspn(str, ",");
 		while (*str == ',')
 			str++;
-- 
2.25.1