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[Stable-8.1.3 32/55] hw/xen: select kernel mode for per-vCPU event chann
From: |
Michael Tokarev |
Subject: |
[Stable-8.1.3 32/55] hw/xen: select kernel mode for per-vCPU event channel upcall vector |
Date: |
Thu, 9 Nov 2023 16:42:36 +0300 |
From: David Woodhouse <dwmw@amazon.co.uk>
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>
(cherry picked from commit 18e83f28bf39ffd2784aeb2e4e229096a86d349b)
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
diff --git a/hw/i386/kvm/xen_evtchn.c b/hw/i386/kvm/xen_evtchn.c
index a731738411..3d6f4b4a0a 100644
--- a/hw/i386/kvm/xen_evtchn.c
+++ b/hw/i386/kvm/xen_evtchn.c
@@ -490,6 +490,12 @@ int xen_evtchn_set_callback_param(uint64_t param)
break;
}
+ /* If the guest has set a per-vCPU callback vector, prefer that. */
+ if (gsi && kvm_xen_has_vcpu_callback_vector()) {
+ in_kernel = kvm_xen_has_cap(EVTCHN_SEND);
+ gsi = 0;
+ }
+
if (!ret) {
/* If vector delivery was turned *off* then tell the kernel */
if ((s->callback_param >> CALLBACK_VIA_TYPE_SHIFT) ==
diff --git a/include/sysemu/kvm_xen.h b/include/sysemu/kvm_xen.h
index 595abfbe40..961c702c4e 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);
diff --git a/target/i386/kvm/xen-emu.c b/target/i386/kvm/xen-emu.c
index 9d512bb859..00941c1c8a 100644
--- a/target/i386/kvm/xen-emu.c
+++ b/target/i386/kvm/xen-emu.c
@@ -424,6 +424,13 @@ void kvm_xen_set_callback_asserted(void)
}
}
+bool kvm_xen_has_vcpu_callback_vector(void)
+{
+ CPUState *cs = qemu_get_cpu(0);
+
+ return cs && !!X86_CPU(cs)->env.xen_vcpu_callback_vector;
+}
+
void kvm_xen_inject_vcpu_callback_vector(uint32_t vcpu_id, int type)
{
CPUState *cs = qemu_get_cpu(vcpu_id);
--
2.39.2
- [Stable-8.1.3 25/55] target/arm: Fix SVE STR increment, (continued)
- [Stable-8.1.3 25/55] target/arm: Fix SVE STR increment, Michael Tokarev, 2023/11/09
- [Stable-8.1.3 22/55] tests/tcg: Add -fno-stack-protector, Michael Tokarev, 2023/11/09
- [Stable-8.1.3 23/55] qemu-img: rebase: stop when reaching EOF of old backing file, Michael Tokarev, 2023/11/09
- [Stable-8.1.3 24/55] qemu-iotests: 024: add rebasing test case for overlay_size > backing_size, Michael Tokarev, 2023/11/09
- [Stable-8.1.3 26/55] target/arm: Correctly propagate stage 1 BTI guarded bit in a two-stage walk, Michael Tokarev, 2023/11/09
- [Stable-8.1.3 28/55] vfio/pci: Fix buffer overrun when writing the VF token, Michael Tokarev, 2023/11/09
- [Stable-8.1.3 27/55] util/uuid: Add UUID_STR_LEN definition, Michael Tokarev, 2023/11/09
- [Stable-8.1.3 29/55] util/uuid: Remove UUID_FMT_LEN, Michael Tokarev, 2023/11/09
- [Stable-8.1.3 30/55] i386/xen: Don't advertise XENFEAT_supervisor_mode_kernel, Michael Tokarev, 2023/11/09
- [Stable-8.1.3 35/55] hw/xen: take iothread mutex in xen_evtchn_reset_op(), Michael Tokarev, 2023/11/09
- [Stable-8.1.3 32/55] hw/xen: select kernel mode for per-vCPU event channel upcall vector,
Michael Tokarev <=
- [Stable-8.1.3 31/55] i386/xen: fix per-vCPU upcall vector for Xen emulation, Michael Tokarev, 2023/11/09
- [Stable-8.1.3 33/55] hw/xen: don't clear map_track[] in xen_gnttab_reset(), Michael Tokarev, 2023/11/09
- [Stable-8.1.3 34/55] hw/xen: fix XenStore watch delivery to guest, Michael Tokarev, 2023/11/09
- [Stable-8.1.3 39/55] target/arm: Fix A64 LDRA immediate decode, Michael Tokarev, 2023/11/09
- [Stable-8.1.3 36/55] hw/xen: use correct default protocol for xen-block on x86, Michael Tokarev, 2023/11/09
- [Stable-8.1.3 37/55] virtio-gpu: block migration of VMs with blob=true, Michael Tokarev, 2023/11/09
- [Stable-8.1.3 38/55] block/nvme: nvme_process_completion() fix bound for cid, Michael Tokarev, 2023/11/09
- [Stable-8.1.3 41/55] block/file-posix: fix update_zones_wp() caller, Michael Tokarev, 2023/11/09
- [Stable-8.1.3 45/55] ui/gtk-egl: apply scale factor when calculating window's dimension, Michael Tokarev, 2023/11/09
- [Stable-8.1.3 40/55] qcow2: keep reference on zeroize with discard-no-unref enabled, Michael Tokarev, 2023/11/09