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authorPaolo Bonzini <pbonzini@redhat.com>2014-02-21 10:32:27 +0100
committerPaolo Bonzini <pbonzini@redhat.com>2014-03-11 10:46:04 +0100
commitfacb0139698923dc7b7d15cafbb319219969f4fd (patch)
treed2f4e83b00ecfc8d744c8f8af5510bca5a8185cc /Documentation
parent5315c716b69f47e1751d09e16c7bd5b559419531 (diff)
KVM: svm: Allow the guest to run with dirty debug registers
When not running in guest-debug mode (i.e. the guest controls the debug registers, having to take an exit for each DR access is a waste of time. If the guest gets into a state where each context switch causes DR to be saved and restored, this can take away as much as 40% of the execution time from the guest. If the guest is running with vcpu->arch.db == vcpu->arch.eff_db, we can let it write freely to the debug registers and reload them on the next exit. We still need to exit on the first access, so that the KVM_DEBUGREG_WONT_EXIT flag is set in switch_db_regs; after that, further accesses to the debug registers will not cause a vmexit. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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