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Subject[PATCH v3] x86, vt-d: enable x2apic opt out
Date
New version of VT-d2 specification (http://download.intel.com/technology
/computing/vptech/Intel(r)_VT_for_Direct_IO.pdf) includes a new feature that
provide firmware a way to request system software to opt out of enable x2APIC
mode. DMAR ACPI table newly define flags.1 bit: x2APIC_OPT_OUT which is set to
request System software opt out xAPIC mode if flags.0 bit:INTR_REMAP is also
set.

This patch enable the feature. Also re-define x2apic_supported() to address
platform x2apic support needs 1)processor has x2apic capability 2)interrupt
remapping support 3)firmware does not request opt-out or ignore the request
by adding kernel option.

Signed-off-by: Youquan Song <youquan.song@intel.com>
Reviewed-by: Kay, Allen M <allen.m.kay@intel.com>
Acked-by: David Woodhouse <David.Woodhouse@intel.com>
---
Documentation/kernel-parameters.txt | 3 +++
arch/x86/include/asm/apic.h | 2 --
arch/x86/kernel/apic/apic.c | 16 ++++++++++++----
drivers/pci/dmar.c | 29 +++++++++++++++++++++++++++--
drivers/pci/intel-iommu.c | 6 ++++++
include/linux/dma_remapping.h | 1 +
include/linux/dmar.h | 3 +++
include/linux/intel-iommu.h | 4 ++++
8 files changed, 56 insertions(+), 8 deletions(-)

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index c603ef7..bc6ec9e 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -999,6 +999,9 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
With this option on every unmap_single operation will
result in a hardware IOTLB flush operation as opposed
to batching them for performance.
+ no_x2apic_optout [Default Off]
+ With this option BIOS x2APIC opt-out request will be
+ ignored.

intremap= [X86-64, Intel-IOMMU]
Format: { on (default) | off | nosid }
diff --git a/arch/x86/include/asm/apic.h b/arch/x86/include/asm/apic.h
index a0c46f0..94d1aed 100644
--- a/arch/x86/include/asm/apic.h
+++ b/arch/x86/include/asm/apic.h
@@ -191,7 +191,6 @@ static inline int x2apic_enabled(void)
return 0;
}

-#define x2apic_supported() (cpu_has_x2apic)
static inline void x2apic_force_phys(void)
{
x2apic_phys = 1;
@@ -212,7 +211,6 @@ static inline void x2apic_force_phys(void)
}

#define x2apic_preenabled 0
-#define x2apic_supported() 0
#endif

extern void enable_IR_x2apic(void);
diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c
index f92a8e5..9a86362 100644
--- a/arch/x86/kernel/apic/apic.c
+++ b/arch/x86/kernel/apic/apic.c
@@ -1462,11 +1462,11 @@ void __init enable_IR_x2apic(void)
{
unsigned long flags;
struct IO_APIC_route_entry **ioapic_entries;
- int ret, x2apic_enabled = 0;
+ int ret = 0, x2apic_enabled = 0;
int dmar_table_init_ret;

dmar_table_init_ret = dmar_table_init();
- if (dmar_table_init_ret && !x2apic_supported())
+ if (dmar_table_init_ret && !cpu_has_x2apic)
return;

ioapic_entries = alloc_ioapic_entries();
@@ -1478,6 +1478,7 @@ void __init enable_IR_x2apic(void)
ret = save_IO_APIC_setup(ioapic_entries);
if (ret) {
pr_info("Saving IO-APIC state failed: %d\n", ret);
+ ret = 0;
goto out;
}

@@ -1504,7 +1505,8 @@ void __init enable_IR_x2apic(void)
x2apic_force_phys();
}

- x2apic_enabled = 1;
+ if (x2apic_supported())
+ x2apic_enabled = 1;

if (x2apic_supported() && !x2apic_mode) {
x2apic_mode = 1;
@@ -1527,8 +1529,14 @@ out:

if (x2apic_preenabled)
panic("x2apic: enabled by BIOS but kernel init failed.");
- else if (cpu_has_x2apic)
+ else if (!ret && cpu_has_x2apic) /* IR enabling failed */
pr_info("Not enabling x2apic, Intr-remapping init failed.\n");
+ else if (!x2apic_supported() && cpu_has_x2apic)
+ WARN(1, "Your BIOS is broken and requested that x2apic be "
+ "disabled.\n This will leave your machine vulnerable to"
+ " irq-injection attacks\n"
+ "Use 'intel_iommu=no_x2apic_optout' to override BIOS "
+ "request\n");
}

#ifdef CONFIG_X86_64
diff --git a/drivers/pci/dmar.c b/drivers/pci/dmar.c
index 12e02bf..c4fe2f9 100644
--- a/drivers/pci/dmar.c
+++ b/drivers/pci/dmar.c
@@ -705,7 +705,7 @@ int __init detect_intel_iommu(void)
* is added, we will not need this any more.
*/
dmar = (struct acpi_table_dmar *) dmar_tbl;
- if (ret && cpu_has_x2apic && dmar->flags & 0x1)
+ if (ret && x2apic_supported() && dmar->flags & DMAR_INTR_REMAP)
printk(KERN_INFO
"Queued invalidation will be enabled to support "
"x2apic and Intr-remapping.\n");
@@ -1461,6 +1461,31 @@ int __init dmar_ir_support(void)
dmar = (struct acpi_table_dmar *)dmar_tbl;
if (!dmar)
return 0;
- return dmar->flags & 0x1;
+ return dmar->flags & DMAR_INTR_REMAP;
}
+
+/*
+ * Check if the platform support x2apic
+ * three necessary conditions:
+ * a. processor support x2apic
+ * b. interrupt remapping support
+ * c. when interrupt reamapping support,firmware does not request to opt out
+ * x2apic by not set x2APIC_OPT_OUT bit at DMAR flags or ignore the request
+ * by adding kernel option.
+ */
+int __init x2apic_supported(void)
+{
+ struct acpi_table_dmar *dmar;
+ unsigned int flags = 0;
+
+ if (!cpu_has_x2apic)
+ return 0;
+
+ dmar = (struct acpi_table_dmar *)dmar_tbl;
+ if (!dmar)
+ return 0;
+ flags = DMAR_INTR_REMAP | (no_x2apic_optout ? 0 : DMAR_X2APIC_OPT_OUT);
+ return ((dmar->flags & flags) == DMAR_INTR_REMAP);
+}
+
IOMMU_INIT_POST(detect_intel_iommu);
diff --git a/drivers/pci/intel-iommu.c b/drivers/pci/intel-iommu.c
index 6af6b62..aa9c69f 100644
--- a/drivers/pci/intel-iommu.c
+++ b/drivers/pci/intel-iommu.c
@@ -383,6 +383,7 @@ int dmar_disabled = 0;
#else
int dmar_disabled = 1;
#endif /*CONFIG_DMAR_DEFAULT_ON*/
+int no_x2apic_optout = 0;

static int dmar_map_gfx = 1;
static int dmar_forcedac;
@@ -417,6 +418,11 @@ static int __init intel_iommu_setup(char *str)
printk(KERN_INFO
"Intel-IOMMU: disable batched IOTLB flush\n");
intel_iommu_strict = 1;
+ } else if (!strncmp(str, "no_x2apic_optout", 16)) {
+ printk(KERN_INFO
+ "Intel-IOMMU: ignore BIOS x2apic opt out "
+ "request\n");
+ no_x2apic_optout = 1;
}

str += strcspn(str, ",");
diff --git a/include/linux/dma_remapping.h b/include/linux/dma_remapping.h
index 5619f85..d2d93d4 100644
--- a/include/linux/dma_remapping.h
+++ b/include/linux/dma_remapping.h
@@ -38,5 +38,6 @@ static inline int iommu_calculate_max_sagaw(struct intel_iommu *iommu)
#endif

extern int dmar_disabled;
+extern int no_x2apic_optout;

#endif
diff --git a/include/linux/dmar.h b/include/linux/dmar.h
index 7b776d7..73c9bff 100644
--- a/include/linux/dmar.h
+++ b/include/linux/dmar.h
@@ -228,8 +228,11 @@ struct dmar_atsr_unit {
};

extern int intel_iommu_init(void);
+extern int x2apic_supported(void);
+
#else /* !CONFIG_DMAR: */
static inline int intel_iommu_init(void) { return -ENODEV; }
+static inline int x2apic_supported(void) { return 0; }
#endif /* CONFIG_DMAR */

#endif /* __DMAR_H__ */
diff --git a/include/linux/intel-iommu.h b/include/linux/intel-iommu.h
index 9310c69..2d086e5 100644
--- a/include/linux/intel-iommu.h
+++ b/include/linux/intel-iommu.h
@@ -29,6 +29,10 @@
#include <asm/cacheflush.h>
#include <asm/iommu.h>

+/* DMAR Flags bits */
+#define DMAR_INTR_REMAP 0x1
+#define DMAR_X2APIC_OPT_OUT 0x2
+
/*
* Intel IOMMU register specification per version 1.0 public spec.
*/
--
1.6.4.2


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