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author | David Woodhouse <dwmw@amazon.co.uk> | 2023-10-12 00:06:26 +0100 |
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committer | David Woodhouse <dwmw@amazon.co.uk> | 2023-11-06 10:03:45 +0000 |
commit | 18e83f28bf39ffd2784aeb2e4e229096a86d349b (patch) | |
tree | d68096ad48ca5dbfc01e1ecb03fcdbf5bcd91f4d /include | |
parent | e7dbb62ff19ce55548c785d76e814e7b144e6217 (diff) | |
download | qemu-18e83f28bf39ffd2784aeb2e4e229096a86d349b.zip qemu-18e83f28bf39ffd2784aeb2e4e229096a86d349b.tar.gz qemu-18e83f28bf39ffd2784aeb2e4e229096a86d349b.tar.bz2 |
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>
Diffstat (limited to 'include')
-rw-r--r-- | include/sysemu/kvm_xen.h | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/include/sysemu/kvm_xen.h b/include/sysemu/kvm_xen.h index 595abfb..961c702 100644 --- a/include/sysemu/kvm_xen.h +++ b/include/sysemu/kvm_xen.h @@ -22,6 +22,7 @@ int kvm_xen_soft_reset(void); uint32_t kvm_xen_get_caps(void); void *kvm_xen_get_vcpu_info_hva(uint32_t vcpu_id); +bool kvm_xen_has_vcpu_callback_vector(void); void kvm_xen_inject_vcpu_callback_vector(uint32_t vcpu_id, int type); void kvm_xen_set_callback_asserted(void); int kvm_xen_set_vcpu_virq(uint32_t vcpu_id, uint16_t virq, uint16_t port); |