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| author | Boris Ostrovsky <boris.ostrovsky@oracle.com> | 2014-12-02 21:19:13 +0100 |
|---|---|---|
| committer | David Vrabel <david.vrabel@citrix.com> | 2014-12-04 14:02:43 +0100 |
| commit | 14520c92cbd7619ae097a3087b140c992b5c270b (patch) | |
| tree | 61a2753722c43559087af44abcce2de742bd8790 /arch/x86/pci/xen.c | |
| parent | xen/pci: Defer initialization of MSI ops on HVM guests (diff) | |
| download | linux-14520c92cbd7619ae097a3087b140c992b5c270b.tar.xz linux-14520c92cbd7619ae097a3087b140c992b5c270b.zip | |
xen/pci: Use APIC directly when APIC virtualization hardware is available
When hardware supports APIC/x2APIC virtualization we don't need to use
pirqs for MSI handling and instead use APIC since most APIC accesses
(MMIO or MSR) will now be processed without VMEXITs.
As an example, netperf on the original code produces this profile
(collected wih 'xentrace -e 0x0008ffff -T 5'):
342 cpu_change
260 CPUID
34638 HLT
64067 INJ_VIRQ
28374 INTR
82733 INTR_WINDOW
10 NPF
24337 TRAP
370610 vlapic_accept_pic_intr
307528 VMENTRY
307527 VMEXIT
140998 VMMCALL
127 wrap_buffer
After applying this patch the same test shows
230 cpu_change
260 CPUID
36542 HLT
174 INJ_VIRQ
27250 INTR
222 INTR_WINDOW
20 NPF
24999 TRAP
381812 vlapic_accept_pic_intr
166480 VMENTRY
166479 VMEXIT
77208 VMMCALL
81 wrap_buffer
ApacheBench results (ab -n 10000 -c 200) improve by about 10%
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Diffstat (limited to 'arch/x86/pci/xen.c')
| -rw-r--r-- | arch/x86/pci/xen.c | 16 |
1 files changed, 16 insertions, 0 deletions
diff --git a/arch/x86/pci/xen.c b/arch/x86/pci/xen.c index 1370716907e1..37914ef19c0a 100644 --- a/arch/x86/pci/xen.c +++ b/arch/x86/pci/xen.c @@ -23,6 +23,8 @@ #include <xen/features.h> #include <xen/events.h> #include <asm/xen/pci.h> +#include <asm/xen/cpuid.h> +#include <asm/apic.h> #include <asm/i8259.h> static int xen_pcifront_enable_irq(struct pci_dev *dev) @@ -434,6 +436,20 @@ int __init pci_xen_init(void) #ifdef CONFIG_PCI_MSI void __init xen_msi_init(void) { + if (!disable_apic) { + /* + * If hardware supports (x2)APIC virtualization (as indicated + * by hypervisor's leaf 4) then we don't need to use pirqs/ + * event channels for MSI handling and instead use regular + * APIC processing + */ + uint32_t eax = cpuid_eax(xen_cpuid_base() + 4); + + if (((eax & XEN_HVM_CPUID_X2APIC_VIRT) && x2apic_mode) || + ((eax & XEN_HVM_CPUID_APIC_ACCESS_VIRT) && cpu_has_apic)) + return; + } + x86_msi.setup_msi_irqs = xen_hvm_setup_msi_irqs; x86_msi.teardown_msi_irq = xen_teardown_msi_irq; } |