Re: [PATCH] enable x2APIC without interrupt remapping under KVM
* Gleb Natapov g...@redhat.com wrote:
+ if (!ret) {
+ /* IR is required if there is APIC ID 255 even when running
+ * under KVM
+ */
Eeek.
+ if (x2apic_preenabled) {
+ panic(x2apic enabled by bios. But IR enabling failed.
+Check that CONFIG_X86_X2APIC and CONFIG_INTR_REMAP are
+enabled.);
We dont want to break such messages mid-line, it makes it hard to
git-grep for them. Also, the '. But' looks weird.
Ingo
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Re: [PATCH] enable x2APIC without interrupt remapping under KVM
On Sun, Jul 19, 2009 at 06:27:35PM +0200, Ingo Molnar wrote:
* Gleb Natapov g...@redhat.com wrote:
+ if (!ret) {
+ /* IR is required if there is APIC ID 255 even when running
+* under KVM
+ */
Eeek.
+ if (x2apic_preenabled) {
+ panic(x2apic enabled by bios. But IR enabling failed.
+ Check that CONFIG_X86_X2APIC and CONFIG_INTR_REMAP are
+ enabled.);
We dont want to break such messages mid-line, it makes it hard to
git-grep for them. Also, the '. But' looks weird.
So what should I do? Make really long line?
--
Gleb.
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Re: [PATCH] enable x2APIC without interrupt remapping under KVM
* Gleb Natapov g...@redhat.com wrote:
On Sun, Jul 19, 2009 at 06:27:35PM +0200, Ingo Molnar wrote:
* Gleb Natapov g...@redhat.com wrote:
+ if (!ret) {
+ /* IR is required if there is APIC ID 255 even when running
+ * under KVM
+ */
Eeek.
+ if (x2apic_preenabled) {
+ panic(x2apic enabled by bios. But IR enabling failed.
+Check that CONFIG_X86_X2APIC and CONFIG_INTR_REMAP are
+enabled.);
We dont want to break such messages mid-line, it makes it hard to
git-grep for them. Also, the '. But' looks weird.
So what should I do? Make really long line?
i'd suggest short ones generally, like:
x2apic: enabled by BIOS but kernel init failed.
also, referring to whether the config are enabled is a bit lame - we
are in the kernel so we should know whether they are enabled.
Ingo
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Re: [PATCH] enable x2APIC without interrupt remapping under KVM
i've only got some small stylistic gripes:
+void __init enable_IR_x2apic(void)
+{
+ unsigned long flags;
+ struct IO_APIC_route_entry **ioapic_entries = NULL;
+ int ret, x2apic_enabled = 0;
+
ioapic_entries = alloc_ioapic_entries();
if (!ioapic_entries) {
- pr_info(Allocate ioapic_entries failed: %d\n, ret);
- goto end;
+ pr_info(Allocate ioapic_entries failed\n);
+ goto out;
That's probably a fatal condition so perhaps a WARN() or pr_err()
would be more appropriate.
+ ret = enable_IR();
+ if (!ret) {
+ /* IR is required if x2apic is enabled by BIOS even
+ * when running in kvm since this indicates present
+ * of APIC ID 255 */
please use the customary (multi-line) comment style:
/*
* Comment .
* .. goes here.
*/
specified in Documentation/CodingStyle.
+ if (max_physical_apicid 255 || !kvm_para_available())
+ goto nox2apic;
+ /* without IR all CPUs can be addressed by IOAPIC/MSI
+ * only in physical mode */
ditto.
+ x2apic_phys = 1;
+ }
- pr_info(Enabled Interrupt-remapping\n);
+ x2apic_enabled = 1;
if (x2apic_supported() !x2apic_mode) {
x2apic_mode = 1;
@@ -1414,41 +1437,30 @@ void __init enable_IR_x2apic(void)
pr_info(Enabled x2apic\n);
}
-end_restore:
- if (ret)
- /*
- * IR enabling failed
- */
+nox2apic:
+ if (!ret) /* IR enabling failed */
restore_IO_APIC_setup(ioapic_entries);
-
unmask_8259A();
local_irq_restore(flags);
-end:
+out:
if (ioapic_entries)
free_ioapic_entries(ioapic_entries);
- if (!ret)
+ if (x2apic_enabled)
return;
-ir_failed:
- if (x2apic_preenabled)
+ if (x2apic_preenabled) {
+#ifdef CONFIG_INTR_REMAP
panic(x2apic enabled by bios. But IR enabling failed);
- else if (cpu_has_x2apic)
- pr_info(Not enabling x2apic,Intr-remapping\n);
#else
- if (!cpu_has_x2apic)
- return;
-
- if (x2apic_preenabled)
panic(x2apic enabled prior OS handover,
-enable CONFIG_X86_X2APIC, CONFIG_INTR_REMAP);
+ enable CONFIG_X86_X2APIC, CONFIG_INTR_REMAP);
#endif
can this #ifdef be avoided?
-
- return;
+ } else if (cpu_has_x2apic)
+ pr_info(Not enabling x2apic,Intr-remapping\n);
please put a space after commas.
Thanks,
Ingo
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Re: [PATCH] enable x2APIC without interrupt remapping under KVM
* Gleb Natapov g...@redhat.com wrote: KVM would like to provide x2APIC interface to a guest without emulating interrupt remapping device. The reason KVM prefers guest to use x2APIC is that x2APIC interface is better virtualizable and provides better performance than mmio xAPIC interface: - msr exits are faster than mmio (no page table walk, emulation) - no need to read back ICR to look at the busy bit - one 64 bit ICR write instead of two 32 bit writes - shared code with the Hyper-V paravirt interface Included patch changes x2APIC enabling logic to enable it even if IR initialization failed, but kernel runs under KVM and no apic id is greater than 255 (if there is one spec requires BIOS to move to x2apic mode before starting an OS). Signed-off-by: Gleb Natapov g...@redhat.com Acked-by: Suresh Siddha suresh.b.sid...@intel.com --- This is the same as v5 only rebased on x86 tree (a74d2cea). Looks good. Small detail: please run the patch through scripts/checkpatch.pl and fix the complaints it has - all 3 details it points out seem like valid complaints to me (at a quick glance) that should be fixed. Thanks, Ingo -- To unsubscribe from this list: send the line unsubscribe kvm in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH] enable x2APIC without interrupt remapping under KVM
On Sunday 28 June 2009 20:51:14 Gleb Natapov wrote:
KVM would like to provide x2APIC interface to a guest without emulating
interrupt remapping device. The reason KVM prefers guest to use x2APIC
is that x2APIC interface is better virtualizable and provides better
performance than mmio xAPIC interface:
- msr exits are faster than mmio (no page table walk, emulation)
- no need to read back ICR to look at the busy bit
- one 64 bit ICR write instead of two 32 bit writes
- shared code with the Hyper-V paravirt interface
Included patch changes x2APIC enabling logic to enable it even if IR
initialization failed, but kernel runs under KVM and no apic id is
greater than 255 (if there is one spec requires BIOS to move to x2apic
mode before starting an OS).
[Resend, sorry for html noise...]
Add Suresh here. And some comments and unclear points below.
Signed-off-by: Gleb Natapov g...@redhat.com
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index d1430ef..7438c5c 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -260,7 +260,7 @@ config SMP
config X86_X2APIC
bool Support x2apic
- depends on X86_LOCAL_APIC X86_64 INTR_REMAP
+ depends on X86_LOCAL_APIC X86_64
---help---
This enables x2apic support on CPUs that have this feature.
We may need to note x2apic won't work without interrupt remapping or as a
guest in KVM here?
diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c
index 8c7c042..48a63b6 100644
--- a/arch/x86/kernel/apic/apic.c
+++ b/arch/x86/kernel/apic/apic.c
@@ -49,6 +49,7 @@
#include asm/mtrr.h
#include asm/smp.h
#include asm/mce.h
+#include asm/kvm_para.h
unsigned int num_processors;
@@ -1363,11 +1364,10 @@ void enable_x2apic(void)
}
#endif /* CONFIG_X86_X2APIC */
-void __init enable_IR_x2apic(void)
+int __init enable_IR(void)
{
#ifdef CONFIG_INTR_REMAP
int ret;
- unsigned long flags;
struct IO_APIC_route_entry **ioapic_entries = NULL;
ret = dmar_table_init();
@@ -1381,11 +1381,10 @@ void __init enable_IR_x2apic(void)
goto ir_failed;
}
-
if (!x2apic_preenabled skip_ioapic_setup) {
pr_info(Skipped enabling intr-remap because of skipping
io-apic setup\n);
- return;
+ goto ir_failed;
}
ioapic_entries = alloc_ioapic_entries();
@@ -1400,22 +1399,14 @@ void __init enable_IR_x2apic(void)
goto end;
}
- local_irq_save(flags);
mask_IO_APIC_setup(ioapic_entries);
- mask_8259A();
ret = enable_intr_remapping(x2apic_supported());
if (ret)
goto end_restore;
-
Unrelated...
pr_info(Enabled Interrupt-remapping\n);
- if (x2apic_supported() !x2apic_mode) {
- x2apic_mode = 1;
- enable_x2apic();
- pr_info(Enabled x2apic\n);
- }
-
+ return 1;
end_restore:
if (ret)
/*
@@ -1423,30 +1414,50 @@ end_restore:
*/
restore_IO_APIC_setup(ioapic_entries);
- unmask_8259A();
- local_irq_restore(flags);
-
end:
if (ioapic_entries)
free_ioapic_entries(ioapic_entries);
- if (!ret)
- return;
-
ir_failed:
- if (x2apic_preenabled)
+#endif
+ return 0;
+}
+
+void __init enable_IR_x2apic(void)
+{
+ unsigned long flags;
+
+ local_irq_save(flags);
+ mask_8259A();
+
+ /* IR is required if x2apic is enabled by BIOS even when running in kvm
+ * since this indicates present of APIC ID 255 */
+ if (!enable_IR() (x2apic_preenabled || !kvm_para_available()))
+ goto nox2apic;
+
Not quite understand the comment here. Could you explain why since this
indicates present of APIC ID 255? In another word, why enable_IR() needed
for KVM even it would be fail at dmar_table_init()?
Another question is, we supposed KVM would use physical mode of x2apic, for
IOAPIC and MSI won't support APIC ID 255. But seems not, or I miss
something?
--
regards
Yang, Sheng
+ if (x2apic_supported() !x2apic_mode) {
+ x2apic_mode = 1;
+ enable_x2apic();
+ pr_info(Enabled x2apic\n);
+ }
+
+ unmask_8259A();
+ local_irq_restore(flags);
+ return;
+
+nox2apic:
+ unmask_8259A();
+ local_irq_restore(flags);
+
+ if (x2apic_preenabled) {
+#ifdef CONFIG_INTR_REMAP
panic(x2apic enabled by bios. But IR enabling failed);
- else if (cpu_has_x2apic)
- pr_info(Not enabling x2apic,Intr-remapping\n);
#else
- if (!cpu_has_x2apic)
- return;
-
- if (x2apic_preenabled)
panic(x2apic enabled prior OS handover,
enable CONFIG_X86_X2APIC, CONFIG_INTR_REMAP);
#endif
-
+ } else if (cpu_has_x2apic)
+ pr_info(Not enabling x2apic,Intr-remapping\n);
return;
}
--
Gleb.
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Re: [PATCH] enable x2APIC without interrupt remapping under KVM
On Mon, Jun 29, 2009 at 03:49:45PM +0800, Sheng Yang wrote:
Signed-off-by: Gleb Natapov g...@redhat.com
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index d1430ef..7438c5c 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -260,7 +260,7 @@ config SMP
config X86_X2APIC
bool Support x2apic
- depends on X86_LOCAL_APIC X86_64 INTR_REMAP
+ depends on X86_LOCAL_APIC X86_64
---help---
This enables x2apic support on CPUs that have this feature.
We may need to note x2apic won't work without interrupt remapping or as a
guest in KVM here?
Will add help text to say this.
diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c
index 8c7c042..48a63b6 100644
--- a/arch/x86/kernel/apic/apic.c
+++ b/arch/x86/kernel/apic/apic.c
@@ -49,6 +49,7 @@
#include asm/mtrr.h
#include asm/smp.h
#include asm/mce.h
+#include asm/kvm_para.h
unsigned int num_processors;
@@ -1363,11 +1364,10 @@ void enable_x2apic(void)
}
#endif /* CONFIG_X86_X2APIC */
-void __init enable_IR_x2apic(void)
+int __init enable_IR(void)
{
#ifdef CONFIG_INTR_REMAP
int ret;
- unsigned long flags;
struct IO_APIC_route_entry **ioapic_entries = NULL;
ret = dmar_table_init();
@@ -1381,11 +1381,10 @@ void __init enable_IR_x2apic(void)
goto ir_failed;
}
-
if (!x2apic_preenabled skip_ioapic_setup) {
pr_info(Skipped enabling intr-remap because of skipping
io-apic setup\n);
- return;
+ goto ir_failed;
}
ioapic_entries = alloc_ioapic_entries();
@@ -1400,22 +1399,14 @@ void __init enable_IR_x2apic(void)
goto end;
}
- local_irq_save(flags);
mask_IO_APIC_setup(ioapic_entries);
- mask_8259A();
ret = enable_intr_remapping(x2apic_supported());
if (ret)
goto end_restore;
-
Unrelated...
pr_info(Enabled Interrupt-remapping\n);
- if (x2apic_supported() !x2apic_mode) {
- x2apic_mode = 1;
- enable_x2apic();
- pr_info(Enabled x2apic\n);
- }
-
+ return 1;
end_restore:
if (ret)
/*
@@ -1423,30 +1414,50 @@ end_restore:
*/
restore_IO_APIC_setup(ioapic_entries);
- unmask_8259A();
- local_irq_restore(flags);
-
end:
if (ioapic_entries)
free_ioapic_entries(ioapic_entries);
- if (!ret)
- return;
-
ir_failed:
- if (x2apic_preenabled)
+#endif
+ return 0;
+}
+
+void __init enable_IR_x2apic(void)
+{
+ unsigned long flags;
+
+ local_irq_save(flags);
+ mask_8259A();
+
+ /* IR is required if x2apic is enabled by BIOS even when running in kvm
+* since this indicates present of APIC ID 255 */
+ if (!enable_IR() (x2apic_preenabled || !kvm_para_available()))
+ goto nox2apic;
+
Not quite understand the comment here. Could you explain why since this
indicates present of APIC ID 255? In another word, why enable_IR() needed
for KVM even it would be fail at dmar_table_init()?
The x2APIC doc says:
The default will be for the BIOS to pass the control to the OS with the
local x2APICs in xAPIC mode if all x2APIC IDs reported by CPUID.0BH:EDX
are less than 255, and in x2APIC mode if there are any logical processor
reporting its x2APIC ID at 255 or greater.
So x2apic_preenabled will be true if there is an APIC ID greater then 255
and in this case we don't want to allow x2APIC use without IR even in KVM
for the reason you mention: IOAPIC and MSI will not be able to address
all CPUs. The reason to try to enable IR first is so that when KVM will
want to support more then 255 CPUs it will be possible to implement IR
device and use existing kernel without additional changes.
Another question is, we supposed KVM would use physical mode of x2apic, for
IOAPIC and MSI won't support APIC ID 255. But seems not, or I miss
something?
Good point. The patch should be fixed to require physical mode for x2apic.
--
Gleb.
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