Searched hist:"18 e83f28" (Results 1 – 3 of 3) sorted by relevance
/openbmc/qemu/include/sysemu/ |
H A D | kvm_xen.h | 18e83f28 Wed Oct 11 18:06:26 CDT 2023 David Woodhouse <dwmw@amazon.co.uk> hw/xen: select kernel mode for per-vCPU event channel upcall vector
A guest which has configured the per-vCPU upcall vector may set the HVM_PARAM_CALLBACK_IRQ param to fairly much anything other than zero.
For example, Linux v6.0+ after commit b1c3497e604 ("x86/xen: Add support for HVMOP_set_evtchn_upcall_vector") will just do this after setting the vector:
/* Trick toolstack to think we are enlightened. */ if (!cpu) rc = xen_set_callback_via(1);
That's explicitly setting the delivery to GSI#1, but it's supposed to be overridden by the per-vCPU vector setting. This mostly works in Qemu *except* for the logic to enable the in-kernel handling of event channels, which falsely determines that the kernel cannot accelerate GSI delivery in this case.
Add a kvm_xen_has_vcpu_callback_vector() to report whether vCPU#0 has the vector set, and use that in xen_evtchn_set_callback_param() to enable the kernel acceleration features even when the param *appears* to be set to target a GSI.
Preserve the Xen behaviour that when HVM_PARAM_CALLBACK_IRQ is set to *zero* the event channel delivery is disabled completely. (Which is what that bizarre guest behaviour is working round in the first place.)
Cc: qemu-stable@nongnu.org Fixes: 91cce756179 ("hw/xen: Add xen_evtchn device for event channel emulation") Signed-off-by: David Woodhouse <dwmw@amazon.co.uk> Reviewed-by: Paul Durrant <paul@xen.org>
|
/openbmc/qemu/hw/i386/kvm/ |
H A D | xen_evtchn.c | 18e83f28 Wed Oct 11 18:06:26 CDT 2023 David Woodhouse <dwmw@amazon.co.uk> hw/xen: select kernel mode for per-vCPU event channel upcall vector
A guest which has configured the per-vCPU upcall vector may set the HVM_PARAM_CALLBACK_IRQ param to fairly much anything other than zero.
For example, Linux v6.0+ after commit b1c3497e604 ("x86/xen: Add support for HVMOP_set_evtchn_upcall_vector") will just do this after setting the vector:
/* Trick toolstack to think we are enlightened. */ if (!cpu) rc = xen_set_callback_via(1);
That's explicitly setting the delivery to GSI#1, but it's supposed to be overridden by the per-vCPU vector setting. This mostly works in Qemu *except* for the logic to enable the in-kernel handling of event channels, which falsely determines that the kernel cannot accelerate GSI delivery in this case.
Add a kvm_xen_has_vcpu_callback_vector() to report whether vCPU#0 has the vector set, and use that in xen_evtchn_set_callback_param() to enable the kernel acceleration features even when the param *appears* to be set to target a GSI.
Preserve the Xen behaviour that when HVM_PARAM_CALLBACK_IRQ is set to *zero* the event channel delivery is disabled completely. (Which is what that bizarre guest behaviour is working round in the first place.)
Cc: qemu-stable@nongnu.org Fixes: 91cce756179 ("hw/xen: Add xen_evtchn device for event channel emulation") Signed-off-by: David Woodhouse <dwmw@amazon.co.uk> Reviewed-by: Paul Durrant <paul@xen.org>
|
/openbmc/qemu/target/i386/kvm/ |
H A D | xen-emu.c | 18e83f28 Wed Oct 11 18:06:26 CDT 2023 David Woodhouse <dwmw@amazon.co.uk> hw/xen: select kernel mode for per-vCPU event channel upcall vector
A guest which has configured the per-vCPU upcall vector may set the HVM_PARAM_CALLBACK_IRQ param to fairly much anything other than zero.
For example, Linux v6.0+ after commit b1c3497e604 ("x86/xen: Add support for HVMOP_set_evtchn_upcall_vector") will just do this after setting the vector:
/* Trick toolstack to think we are enlightened. */ if (!cpu) rc = xen_set_callback_via(1);
That's explicitly setting the delivery to GSI#1, but it's supposed to be overridden by the per-vCPU vector setting. This mostly works in Qemu *except* for the logic to enable the in-kernel handling of event channels, which falsely determines that the kernel cannot accelerate GSI delivery in this case.
Add a kvm_xen_has_vcpu_callback_vector() to report whether vCPU#0 has the vector set, and use that in xen_evtchn_set_callback_param() to enable the kernel acceleration features even when the param *appears* to be set to target a GSI.
Preserve the Xen behaviour that when HVM_PARAM_CALLBACK_IRQ is set to *zero* the event channel delivery is disabled completely. (Which is what that bizarre guest behaviour is working round in the first place.)
Cc: qemu-stable@nongnu.org Fixes: 91cce756179 ("hw/xen: Add xen_evtchn device for event channel emulation") Signed-off-by: David Woodhouse <dwmw@amazon.co.uk> Reviewed-by: Paul Durrant <paul@xen.org>
|