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

Sean Christopherson
2021-02-23T23:15:43Z

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.

> + (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")

> + 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
>