[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] [PATCH v4 0/2] xen/pci: Use APIC for MSIs when APIC virtualization is supported
Changes in v4: * Added comment describing what we check for in pci_xen_init() Changes in v3: * Explicitly include asm/apic.h in arch/x86/pci/xen.c for !CONFIG_SMP. Changes in v2: * New version of cpuid.h file from Xen tree (with a couple of style adjustments) * Whitespace cleanup Currently HVM guests handle MSI interrupts using pirqs/event channels, allowing us to not issue APIC accesses that result in somewhat expensive VMEXITs. When hardware supports APIC virtualization we don't need to use pirqs anymore since now guest's APIC accesses can be handled by the processor itself. There are two patches in this series: 1. Move setting of x86_msi ops to a later point. The reason for doing so is that we currently decide whether or not to use pirqs before kernel had a chance to see whether it should be using x2APIC instead of plain APIC. Since hardware may virtualize either or both of those two we can only make pirqs vs. APIC selection after kernel has settled down on which APIC version it will use. (Note that currently x2APIC is not used by HVM guests so technically this patch is not necessary. However, it probably makes sense to apply it now to avoid forgetting to do it when we enable x2APIC). 2. Set x86_msi ops to use pirqs only when APIC virtualization is not available. The commit message describes performance improvements that this change brings. Boris Ostrovsky (2): xen/pci: Defer initialization of MSI ops on HVM guests until after x2APIC has been set up xen/pci: Use APIC directly when APIC virtualization is supported by hardware arch/x86/include/asm/xen/cpuid.h | 91 ++++++++++++++++++++++++++++++++++++++++ arch/x86/pci/xen.c | 31 +++++++++++++- 2 files changed, 120 insertions(+), 2 deletions(-) create mode 100644 arch/x86/include/asm/xen/cpuid.h -- 1.8.1.4 _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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