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SubjectRe: [PATCH] KVM: vmx: print more APICv fields in dump_vmcs
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On 15/04/19 20:39, Sean Christopherson wrote:
> On Mon, Apr 15, 2019 at 03:35:32PM +0200, Paolo Bonzini wrote:
>> The SVI, RVI, virtual-APIC page address and APIC-access page address fields
>> were left out of dump_vmcs. Add them.
>>
>> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
>> ---
>> arch/x86/kvm/vmx/vmx.c | 13 +++++++++++--
>> 1 file changed, 11 insertions(+), 2 deletions(-)
>>
>> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
>> index ab432a930ae8..f8054dc1de65 100644
>> --- a/arch/x86/kvm/vmx/vmx.c
>> +++ b/arch/x86/kvm/vmx/vmx.c
>> @@ -5723,8 +5723,17 @@ static void dump_vmcs(void)
>> if (secondary_exec_control & SECONDARY_EXEC_TSC_SCALING)
>> pr_err("TSC Multiplier = 0x%016llx\n",
>> vmcs_read64(TSC_MULTIPLIER));
>> - if (cpu_based_exec_ctrl & CPU_BASED_TPR_SHADOW)
>> - pr_err("TPR Threshold = 0x%02x\n", vmcs_read32(TPR_THRESHOLD));
>> + if (cpu_based_exec_ctrl & CPU_BASED_TPR_SHADOW) {
>> + if (secondary_exec_control & SECONDARY_EXEC_VIRTUAL_INTR_DELIVERY) {
>> + u16 status = vmcs_read16(GUEST_INTR_STATUS);
>> + pr_err("SVI|RVI = %02x|%02x ", status >> 8, status & 0xff);
>> + }
>> + pr_err(KERN_CONT "TPR Threshold = 0x%02x\n", vmcs_read32(TPR_THRESHOLD));
>
> Might be worth adding a blurb in the changelog stating it's ok to use
> KERN_CONT even though it's technically not SMP safe, as the whole
> dump_vmcs() flow isn't exactly SMP safe.
>
>> + if (secondary_exec_control & (SECONDARY_EXEC_VIRTUALIZE_APIC_ACCESSES |
>> + SECONDARY_EXEC_VIRTUALIZE_X2APIC_MODE))
>
> Do we really want to dump the APIC access page address for x2APIC? I
> assume your intent is to show the value that *could* be used if the guest
> were to disable x2APIC, but that might be misleading since APIC_ACCESS_ADDR
> is checked if and only if VIRTUALIZE_APIC_ACCESSES=1, e.g. someone might
> think a VM-Enter failed because APIC_ACCESS_ADDR has a "bad" value even
> though it's ignored.

Indeed, brain fart. It's the virtual-APIC page that matters for virtual
x2APIC mode, and that one indeed is printed below (because virtual
x2APIC requires TPR shadow).

Paolo

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