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| author | donsheng <dongsheng.x.zhang@intel.com> | 2024-05-22 04:01:14 +0800 |
|---|---|---|
| committer | Michael Tokarev <mjt@tls.msk.ru> | 2024-05-27 07:37:34 +0300 |
| commit | 285cef5c3944efac176cef60036748184d1bf5af (patch) | |
| tree | 0e37a35b94d3cc159d5baaa8aa62806838ee95dd /target | |
| parent | 2569dec929737f8bef4b9e1501ff0e41acf7af3c (diff) | |
target-i386: hyper-v: Correct kvm_hv_handle_exit return value
This bug fix addresses the incorrect return value of kvm_hv_handle_exit for
KVM_EXIT_HYPERV_SYNIC, which should be EXCP_INTERRUPT.
Handling of KVM_EXIT_HYPERV_SYNIC in QEMU needs to be synchronous.
This means that async_synic_update should run in the current QEMU vCPU
thread before returning to KVM, returning EXCP_INTERRUPT to guarantee this.
Returning 0 can cause async_synic_update to run asynchronously.
One problem (kvm-unit-tests's hyperv_synic test fails with timeout error)
caused by this bug:
When a guest VM writes to the HV_X64_MSR_SCONTROL MSR to enable Hyper-V SynIC,
a VM exit is triggered and processed by the kvm_hv_handle_exit function of the
QEMU vCPU. This function then calls the async_synic_update function to set
synic->sctl_enabled to true. A true value of synic->sctl_enabled is required
before creating SINT routes using the hyperv_sint_route_new() function.
If kvm_hv_handle_exit returns 0 for KVM_EXIT_HYPERV_SYNIC, the current QEMU
vCPU thread may return to KVM and enter the guest VM before running
async_synic_update. In such case, the hyperv_synic test’s subsequent call to
synic_ctl(HV_TEST_DEV_SINT_ROUTE_CREATE, ...) immediately after writing to
HV_X64_MSR_SCONTROL can cause QEMU’s hyperv_sint_route_new() function to return
prematurely (because synic->sctl_enabled is false).
If the SINT route is not created successfully, the SINT interrupt will not be
fired, resulting in a timeout error in the hyperv_synic test.
Fixes: 267e071bd6d6 (“hyperv: make overlay pages for SynIC”)
Suggested-by: Chao Gao <chao.gao@intel.com>
Signed-off-by: Dongsheng Zhang <dongsheng.x.zhang@intel.com>
Message-ID: <20240521200114.11588-1-dongsheng.x.zhang@intel.com>
Cc: qemu-stable@nongnu.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
(cherry picked from commit 84d4b72854869821eb89813c195927fdd3078c12)
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
Diffstat (limited to 'target')
| -rw-r--r-- | target/i386/kvm/hyperv.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/target/i386/kvm/hyperv.c b/target/i386/kvm/hyperv.c index f2a3fe650a..b94f12acc2 100644 --- a/target/i386/kvm/hyperv.c +++ b/target/i386/kvm/hyperv.c @@ -81,7 +81,7 @@ int kvm_hv_handle_exit(X86CPU *cpu, struct kvm_hyperv_exit *exit) */ async_safe_run_on_cpu(CPU(cpu), async_synic_update, RUN_ON_CPU_NULL); - return 0; + return EXCP_INTERRUPT; case KVM_EXIT_HYPERV_HCALL: { uint16_t code = exit->u.hcall.input & 0xffff; bool fast = exit->u.hcall.input & HV_HYPERCALL_FAST; |