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authordonsheng <dongsheng.x.zhang@intel.com>2024-05-22 04:01:14 +0800
committerMichael Tokarev <mjt@tls.msk.ru>2024-05-27 07:37:34 +0300
commit285cef5c3944efac176cef60036748184d1bf5af (patch)
tree0e37a35b94d3cc159d5baaa8aa62806838ee95dd
parent2569dec929737f8bef4b9e1501ff0e41acf7af3c (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>
-rw-r--r--target/i386/kvm/hyperv.c2
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;