Re: [PATCH v2 2/3] KVM: x86: dump_vmcs should not conflate EFER and PAT presence in VMCS

David Edmondson
2021-02-24T14:51:48Z

On Tuesday, 2021-02-23 at 14:58:29 -08, Sean Christopherson wrote:

> On Fri, Feb 19, 2021, David Edmondson wrote:
>> Show EFER and PAT based on their individual entry/exit controls.
>>
>> Signed-off-by: David Edmondson <david.edmondson@oracle.com>
>> ---
>> arch/x86/kvm/vmx/vmx.c | 19 ++++++++++---------
>> 1 file changed, 10 insertions(+), 9 deletions(-)
>>
>> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
>> index 818051c9fa10..25090e3683ca 100644
>> --- a/arch/x86/kvm/vmx/vmx.c
>> +++ b/arch/x86/kvm/vmx/vmx.c
>> @@ -5805,11 +5805,12 @@ void dump_vmcs(void)
>> vmx_dump_sel("LDTR:", GUEST_LDTR_SELECTOR);
>> vmx_dump_dtsel("IDTR:", GUEST_IDTR_LIMIT);
>> vmx_dump_sel("TR: ", GUEST_TR_SELECTOR);
>> - if ((vmexit_ctl & (VM_EXIT_SAVE_IA32_PAT | VM_EXIT_SAVE_IA32_EFER)) ||
>> - (vmentry_ctl & (VM_ENTRY_LOAD_IA32_PAT | VM_ENTRY_LOAD_IA32_EFER)))
>> - pr_err("EFER = 0x%016llx PAT = 0x%016llx\n",
>> - vmcs_read64(GUEST_IA32_EFER),
>> - vmcs_read64(GUEST_IA32_PAT));
>> + if ((vmexit_ctl & VM_EXIT_SAVE_IA32_EFER) ||
>
> Not your code, and completely benign since VM_EXIT_SAVE is never set, but I
> don't like checking the VM_EXIT_SAVE_* flag as saving a field on VM-Exit has
> zero impact on whether VM-Entry succeeds or fails. Same complaint on the PAT
> field.

Added to v3.

>> + (vmentry_ctl & VM_ENTRY_LOAD_IA32_EFER))
>> + pr_err("EFER= 0x%016llx\n", vmcs_read64(GUEST_IA32_EFER));
>
> Tying into the previous patch, I think we should print both the effective EFER
> and vmcs.EFER. The effective EFER is relevant for several consistency checks.
> Maybe something like this?
>
> pr_err("EFER= 0x%016llx ", effective_efer);
> if (vmentry_ctl & VM_ENTRY_LOAD_IA32_EFER)
> pr_cont("vmcs.EFER= 0x%016llx\n", vmcs_read64(GUEST_IA32_EFER));
> else
> pr_cont("vmcs.EFER not loaded\n")

Added something similar, that makes it clear where the value came from,
in v3.

>> + if ((vmexit_ctl & VM_EXIT_SAVE_IA32_PAT) ||
>> + (vmentry_ctl & VM_ENTRY_LOAD_IA32_PAT))
>> + pr_err("PAT = 0x%016llx\n", vmcs_read64(GUEST_IA32_PAT));
>> pr_err("DebugCtl = 0x%016llx DebugExceptions = 0x%016lx\n",
>> vmcs_read64(GUEST_IA32_DEBUGCTL),
>> vmcs_readl(GUEST_PENDING_DBG_EXCEPTIONS));
>> @@ -5846,10 +5847,10 @@ void dump_vmcs(void)
>> vmcs_readl(HOST_IA32_SYSENTER_ESP),
>> vmcs_read32(HOST_IA32_SYSENTER_CS),
>> vmcs_readl(HOST_IA32_SYSENTER_EIP));
>> - if (vmexit_ctl & (VM_EXIT_LOAD_IA32_PAT | VM_EXIT_LOAD_IA32_EFER))
>> - pr_err("EFER = 0x%016llx PAT = 0x%016llx\n",
>> - vmcs_read64(HOST_IA32_EFER),
>> - vmcs_read64(HOST_IA32_PAT));
>> + if (vmexit_ctl & VM_EXIT_LOAD_IA32_EFER)
>> + pr_err("EFER= 0x%016llx\n", vmcs_read64(HOST_IA32_EFER));
>> + if (vmexit_ctl & VM_EXIT_LOAD_IA32_PAT)
>> + pr_err("PAT = 0x%016llx\n", vmcs_read64(HOST_IA32_PAT));
>> if (cpu_has_load_perf_global_ctrl() &&
>> vmexit_ctl & VM_EXIT_LOAD_IA32_PERF_GLOBAL_CTRL)
>> pr_err("PerfGlobCtl = 0x%016llx\n",
>> --
>> 2.30.0
>>

dme.
--
And the sign said: long haired freaky people need not apply.