[tip: x86/irq] iommu/vt-d: Make posted MSI an opt-in command line option

[tip-bot2 for Jacob Pan]

The following commit has been merged into the x86/irq branch of tip:

Commit-ID:     be9be07b22c96dc03d0ecc76b5a5f21c2dcb05a1
Gitweb:        https://git.kernel.org/tip/be9be07b22c96dc03d0ecc76b5a5f21c2dcb05a1
Author:        Jacob Pan <jacob.jun.pan@xxxxxxxxxxxxxxx>
AuthorDate:    Tue, 23 Apr 2024 10:41:13 -07:00
Committer:     Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CommitterDate: Tue, 30 Apr 2024 00:54:43 +02:00

iommu/vt-d: Make posted MSI an opt-in command line option

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@xxxxxxxxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20240423174114.526704-12-jacob.jun.pan@xxxxxxxxxxxxxxx


---
 Documentation/admin-guide/kernel-parameters.txt | 2 ++
 arch/x86/include/asm/irq_remapping.h            | 7 +++++++
 drivers/iommu/irq_remapping.c                   | 5 ++++-
 3 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 902ecd9..dfbe9fd 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -2251,6 +2251,8 @@
 			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 7a2ed15..5036f13 100644
--- a/arch/x86/include/asm/irq_remapping.h
+++ b/arch/x86/include/asm/irq_remapping.h
@@ -50,6 +50,13 @@ static inline struct irq_domain *arch_get_ir_parent_domain(void)
 	return x86_vector_domain;
 }
 
+extern bool enable_posted_msi;
+
+static inline bool posted_msi_supported(void)
+{
+	return enable_posted_msi && irq_remapping_cap(IRQ_POSTING_CAP);
+}
+
 #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 ee59647..056fec6 100644
--- a/drivers/iommu/irq_remapping.c
+++ b/drivers/iommu/irq_remapping.c
@@ -24,6 +24,8 @@ int no_x2apic_optout;
 
 int disable_irq_post = 0;
 
+bool enable_posted_msi __ro_after_init;
+
 static int disable_irq_remap;
 static struct irq_remap_ops *remap_ops;
 
@@ -70,7 +72,8 @@ static __init int setup_irqremap(char *str)
 			no_x2apic_optout = 1;
 		else if (!strncmp(str, "nopost", 6))
 			disable_irq_post = 1;
-
+		else if (IS_ENABLED(CONFIG_X86_POSTED_MSI) && !strncmp(str, "posted_msi", 10))
+			enable_posted_msi = true;
 		str += strcspn(str, ",");
 		while (*str == ',')
 			str++;