From: Mohamed Mediouni Date: Wed, 22 Apr 2026 21:41:50 +0000 (+0200) Subject: whpx: i386: x2apic emulation X-Git-Tag: v11.1.0-rc0~141^2~34 X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=ba1bda25b7cf57dd00712c91eedfa9314e2fe30a;p=thirdparty%2Fqemu.git whpx: i386: x2apic emulation Add x2apic emulation to WHPX for the kernel-irqchip=off case. Unfortunately, it looks like there isn't a workaround available for proper behavior of PIC interrupts when kernel-irqchip=on for Windows 10. The OS is out of support outside of extended security updates so this will not be addressed. The performance boost is quite visible for multicore guests. Signed-off-by: Mohamed Mediouni Link: https://lore.kernel.org/r/20260422214225.2242-3-mohamed@unpredictable.fr Signed-off-by: Paolo Bonzini --- diff --git a/target/i386/whpx/whpx-all.c b/target/i386/whpx/whpx-all.c index e56ae2b3433..4127440c0ca 100644 --- a/target/i386/whpx/whpx-all.c +++ b/target/i386/whpx/whpx-all.c @@ -1082,6 +1082,8 @@ HRESULT whpx_set_exception_exit_bitmap(UINT64 exceptions) /* Register for MSR and CPUID exits */ memset(&prop, 0, sizeof(WHV_PARTITION_PROPERTY)); prop.ExtendedVmExits.X64MsrExit = 1; + prop.ExtendedVmExits.X64CpuidExit = 1; + if (exceptions != 0) { prop.ExtendedVmExits.ExceptionExit = 1; } @@ -1898,6 +1900,18 @@ int whpx_vcpu_run(CPUState *cpu) WHV_REGISTER_NAME reg_names[3]; UINT32 reg_count; bool is_known_msr = 0; + uint64_t val; + + if (vcpu->exit_ctx.MsrAccess.AccessInfo.IsWrite) { + val = ((uint32_t)vcpu->exit_ctx.MsrAccess.Rax) | + ((uint64_t)(vcpu->exit_ctx.MsrAccess.Rdx) << 32); + } else { + /* + * Workaround for [-Werror=maybe-uninitialized] + * with GCC. Not needed with Clang. + */ + val = 0; + } reg_names[0] = WHvX64RegisterRip; reg_names[1] = WHvX64RegisterRax; @@ -1911,7 +1925,47 @@ int whpx_vcpu_run(CPUState *cpu) && !vcpu->exit_ctx.MsrAccess.AccessInfo.IsWrite && !whpx_irqchip_in_kernel()) { is_known_msr = 1; - reg_values[1].Reg32 = (uint32_t)X86_CPU(cpu)->env.apic_bus_freq; + val = X86_CPU(cpu)->env.apic_bus_freq; + } + + if (!whpx_irqchip_in_kernel() && + vcpu->exit_ctx.MsrAccess.MsrNumber == MSR_IA32_APICBASE) { + is_known_msr = 1; + if (!vcpu->exit_ctx.MsrAccess.AccessInfo.IsWrite) { + /* Read path unreachable on Hyper-V */ + abort(); + } else { + WHV_REGISTER_VALUE reg = {.Reg64 = val}; + int msr_ret = cpu_set_apic_base(X86_CPU(cpu)->apic_state, val); + if (msr_ret < 0) { + x86_emul_raise_exception(&X86_CPU(cpu)->env, EXCP0D_GPF, 0); + } + whpx_set_reg(cpu, WHvX64RegisterApicBase, reg); + } + } + + if (!whpx_irqchip_in_kernel() && + vcpu->exit_ctx.MsrAccess.MsrNumber >= MSR_APIC_START && + vcpu->exit_ctx.MsrAccess.MsrNumber <= MSR_APIC_END) { + int index = vcpu->exit_ctx.MsrAccess.MsrNumber - MSR_APIC_START; + int msr_ret; + is_known_msr = 1; + if (!vcpu->exit_ctx.MsrAccess.AccessInfo.IsWrite) { + bql_lock(); + msr_ret = apic_msr_read(X86_CPU(cpu)->apic_state, index, &val); + bql_unlock(); + reg_values[1].Reg64 = val; + if (msr_ret < 0) { + x86_emul_raise_exception(&X86_CPU(cpu)->env, EXCP0D_GPF, 0); + } + } else { + bql_lock(); + msr_ret = apic_msr_write(X86_CPU(cpu)->apic_state, index, val); + bql_unlock(); + if (msr_ret < 0) { + x86_emul_raise_exception(&X86_CPU(cpu)->env, EXCP0D_GPF, 0); + } + } } /* * For all unsupported MSR access we: @@ -1921,6 +1975,11 @@ int whpx_vcpu_run(CPUState *cpu) reg_count = vcpu->exit_ctx.MsrAccess.AccessInfo.IsWrite ? 1 : 3; + if (!vcpu->exit_ctx.MsrAccess.AccessInfo.IsWrite) { + reg_values[1].Reg32 = (uint32_t)val; + reg_values[2].Reg32 = (uint32_t)(val >> 32); + } + if (!is_known_msr) { trace_whpx_unsupported_msr_access(vcpu->exit_ctx.MsrAccess.MsrNumber, vcpu->exit_ctx.MsrAccess.AccessInfo.IsWrite); @@ -1939,6 +1998,47 @@ int whpx_vcpu_run(CPUState *cpu) ret = 0; break; } + case WHvRunVpExitReasonX64Cpuid: { + WHV_REGISTER_VALUE reg_values[5] = {0}; + WHV_REGISTER_NAME reg_names[5]; + UINT32 reg_count = 5; + X86CPU *x86_cpu = X86_CPU(cpu); + CPUX86State *env = &x86_cpu->env; + + reg_names[0] = WHvX64RegisterRip; + reg_names[1] = WHvX64RegisterRax; + reg_names[2] = WHvX64RegisterRcx; + reg_names[3] = WHvX64RegisterRdx; + reg_names[4] = WHvX64RegisterRbx; + + reg_values[0].Reg64 = + vcpu->exit_ctx.VpContext.Rip + + vcpu->exit_ctx.VpContext.InstructionLength; + + reg_values[1].Reg64 = vcpu->exit_ctx.CpuidAccess.DefaultResultRax; + reg_values[2].Reg64 = vcpu->exit_ctx.CpuidAccess.DefaultResultRcx; + reg_values[3].Reg64 = vcpu->exit_ctx.CpuidAccess.DefaultResultRdx; + reg_values[4].Reg64 = vcpu->exit_ctx.CpuidAccess.DefaultResultRbx; + + if (vcpu->exit_ctx.CpuidAccess.Rax == 1) { + if (cpu_has_x2apic_feature(env)) { + reg_values[2].Reg64 |= CPUID_EXT_X2APIC; + } + } + + hr = whp_dispatch.WHvSetVirtualProcessorRegisters( + whpx->partition, + cpu->cpu_index, + reg_names, reg_count, + reg_values); + + if (FAILED(hr)) { + error_report("WHPX: Failed to set CpuidAccess state " + " registers, hr=%08lx", hr); + } + ret = 0; + break; + } case WHvRunVpExitReasonException: whpx_get_registers(cpu, WHPX_LEVEL_FULL_STATE); @@ -2136,6 +2236,7 @@ int whpx_accel_init(AccelState *as, MachineState *ms) WHV_PROCESSOR_FEATURES_BANKS processor_features; WHV_PROCESSOR_PERFMON_FEATURES perfmon_features; bool is_legacy_os = false; + UINT32 cpuidExitList[] = {1}; whpx = &whpx_global; @@ -2354,6 +2455,7 @@ int whpx_accel_init(AccelState *as, MachineState *ms) /* Register for MSR and CPUID exits */ memset(&prop, 0, sizeof(WHV_PARTITION_PROPERTY)); prop.ExtendedVmExits.X64MsrExit = 1; + prop.ExtendedVmExits.X64CpuidExit = 1; hr = whp_dispatch.WHvSetPartitionProperty( whpx->partition, @@ -2366,6 +2468,36 @@ int whpx_accel_init(AccelState *as, MachineState *ms) goto error; } + memset(&prop, 0, sizeof(WHV_PARTITION_PROPERTY)); + prop.X64MsrExitBitmap.UnhandledMsrs = 1; + if (!whpx_irqchip_in_kernel()) { + prop.X64MsrExitBitmap.ApicBaseMsrWrite = 1; + } + + hr = whp_dispatch.WHvSetPartitionProperty( + whpx->partition, + WHvPartitionPropertyCodeX64MsrExitBitmap, + &prop, + sizeof(WHV_PARTITION_PROPERTY)); + if (FAILED(hr)) { + error_report("WHPX: Failed to set MSR exit bitmap, hr=%08lx", hr); + ret = -EINVAL; + goto error; + } + + hr = whp_dispatch.WHvSetPartitionProperty( + whpx->partition, + WHvPartitionPropertyCodeCpuidExitList, + cpuidExitList, + RTL_NUMBER_OF(cpuidExitList) * sizeof(UINT32)); + + if (FAILED(hr)) { + error_report("WHPX: Failed to set partition CpuidExitList hr=%08lx", + hr); + ret = -EINVAL; + goto error; + } + /* * We do not want to intercept any exceptions from the guest, * until we actually start debugging with gdb.