[PATCH 12/15] iommu/vt-d: Make posted MSI an opt-in cmdline option

Jacob Pan
2024-01-26T23:37:30Z

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 31b3a25680d0..35feefc0bdb0 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -2212,6 +2212,7 @@
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 83314b9d8f38..4047ac396728 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