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Date: Fri, 08 Jul 2022 14:23:43 +1200
From: Kai Huang <kai.huang@...el.com>
To: isaku.yamahata@...el.com, kvm@...r.kernel.org,
linux-kernel@...r.kernel.org
Cc: isaku.yamahata@...il.com, Paolo Bonzini <pbonzini@...hat.com>
Subject: Re: [PATCH v7 041/102] KVM: VMX: Introduce test mode related to EPT
violation VE
On Mon, 2022-06-27 at 14:53 -0700, isaku.yamahata@...el.com wrote:
> From: Isaku Yamahata <isaku.yamahata@...el.com>
>
> To support TDX, KVM is enhanced to operate with #VE. For TDX, KVM programs
> to inject #VE conditionally and set #VE suppress bit in EPT entry. For VMX
> case, #VE isn't used. If #VE happens for VMX, it's a bug. To be
> defensive (test that VMX case isn't broken), introduce option
> ept_violation_ve_test and when it's set, set error.
I don't see why we need this patch. It may be helpful during your test, but why
do we need this patch for formal submission?
And for a normal guest, what prevents one vcpu from sending #VE IPI to another
vcpu?
>
> Signed-off-by: Isaku Yamahata <isaku.yamahata@...el.com>
> ---
> arch/x86/include/asm/vmx.h | 12 +++++++
> arch/x86/kvm/vmx/vmx.c | 68 +++++++++++++++++++++++++++++++++++++-
> arch/x86/kvm/vmx/vmx.h | 3 ++
> 3 files changed, 82 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/include/asm/vmx.h b/arch/x86/include/asm/vmx.h
> index 6231ef005a50..f0f8eecf55ac 100644
> --- a/arch/x86/include/asm/vmx.h
> +++ b/arch/x86/include/asm/vmx.h
> @@ -68,6 +68,7 @@
> #define SECONDARY_EXEC_ENCLS_EXITING VMCS_CONTROL_BIT(ENCLS_EXITING)
> #define SECONDARY_EXEC_RDSEED_EXITING VMCS_CONTROL_BIT(RDSEED_EXITING)
> #define SECONDARY_EXEC_ENABLE_PML VMCS_CONTROL_BIT(PAGE_MOD_LOGGING)
> +#define SECONDARY_EXEC_EPT_VIOLATION_VE VMCS_CONTROL_BIT(EPT_VIOLATION_VE)
> #define SECONDARY_EXEC_PT_CONCEAL_VMX VMCS_CONTROL_BIT(PT_CONCEAL_VMX)
> #define SECONDARY_EXEC_XSAVES VMCS_CONTROL_BIT(XSAVES)
> #define SECONDARY_EXEC_MODE_BASED_EPT_EXEC VMCS_CONTROL_BIT(MODE_BASED_EPT_EXEC)
> @@ -223,6 +224,8 @@ enum vmcs_field {
> VMREAD_BITMAP_HIGH = 0x00002027,
> VMWRITE_BITMAP = 0x00002028,
> VMWRITE_BITMAP_HIGH = 0x00002029,
> + VE_INFORMATION_ADDRESS = 0x0000202A,
> + VE_INFORMATION_ADDRESS_HIGH = 0x0000202B,
> XSS_EXIT_BITMAP = 0x0000202C,
> XSS_EXIT_BITMAP_HIGH = 0x0000202D,
> ENCLS_EXITING_BITMAP = 0x0000202E,
> @@ -628,4 +631,13 @@ enum vmx_l1d_flush_state {
>
> extern enum vmx_l1d_flush_state l1tf_vmx_mitigation;
>
> +struct vmx_ve_information {
> + u32 exit_reason;
> + u32 delivery;
> + u64 exit_qualification;
> + u64 guest_linear_address;
> + u64 guest_physical_address;
> + u16 eptp_index;
> +};
> +
> #endif
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index e2415ac55317..e3d304b14df0 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -126,6 +126,9 @@ module_param(error_on_inconsistent_vmcs_config, bool, 0444);
> static bool __read_mostly dump_invalid_vmcs = 0;
> module_param(dump_invalid_vmcs, bool, 0644);
>
> +static bool __read_mostly ept_violation_ve_test = 0;
> +module_param(ept_violation_ve_test, bool, 0444);
> +
> #define MSR_BITMAP_MODE_X2APIC 1
> #define MSR_BITMAP_MODE_X2APIC_APICV 2
>
> @@ -726,6 +729,13 @@ void vmx_update_exception_bitmap(struct kvm_vcpu *vcpu)
>
> eb = (1u << PF_VECTOR) | (1u << UD_VECTOR) | (1u << MC_VECTOR) |
> (1u << DB_VECTOR) | (1u << AC_VECTOR);
> + /*
> + * #VE isn't used for VMX, but for TDX. To test against unexpected
> + * change related to #VE for VMX, intercept unexpected #VE and warn on
> + * it.
> + */
> + if (ept_violation_ve_test)
> + eb |= 1u << VE_VECTOR;
> /*
> * Guest access to VMware backdoor ports could legitimately
> * trigger #GP because of TSS I/O permission bitmap.
> @@ -2524,6 +2534,8 @@ static int setup_vmcs_config(struct vmcs_config *vmcs_conf,
> SECONDARY_EXEC_NOTIFY_VM_EXITING;
> if (cpu_has_sgx())
> opt2 |= SECONDARY_EXEC_ENCLS_EXITING;
> + if (ept_violation_ve_test)
> + opt2 |= SECONDARY_EXEC_EPT_VIOLATION_VE;
> if (adjust_vmx_controls(min2, opt2,
> MSR_IA32_VMX_PROCBASED_CTLS2,
> &_cpu_based_2nd_exec_control) < 0)
> @@ -2558,6 +2570,7 @@ static int setup_vmcs_config(struct vmcs_config *vmcs_conf,
> return -EIO;
>
> vmx_cap->ept = 0;
> + _cpu_based_2nd_exec_control &= ~SECONDARY_EXEC_EPT_VIOLATION_VE;
> }
> if (!(_cpu_based_2nd_exec_control & SECONDARY_EXEC_ENABLE_VPID) &&
> vmx_cap->vpid) {
> @@ -4390,6 +4403,7 @@ static u32 vmx_secondary_exec_control(struct vcpu_vmx *vmx)
> exec_control &= ~SECONDARY_EXEC_ENABLE_VPID;
> if (!enable_ept) {
> exec_control &= ~SECONDARY_EXEC_ENABLE_EPT;
> + exec_control &= ~SECONDARY_EXEC_EPT_VIOLATION_VE;
> enable_unrestricted_guest = 0;
> }
> if (!enable_unrestricted_guest)
> @@ -4517,8 +4531,40 @@ static void init_vmcs(struct vcpu_vmx *vmx)
>
> exec_controls_set(vmx, vmx_exec_control(vmx));
>
> - if (cpu_has_secondary_exec_ctrls())
> + if (cpu_has_secondary_exec_ctrls()) {
> secondary_exec_controls_set(vmx, vmx_secondary_exec_control(vmx));
> + if (secondary_exec_controls_get(vmx) &
> + SECONDARY_EXEC_EPT_VIOLATION_VE) {
> + if (!vmx->ve_info) {
> + /* ve_info must be page aligned. */
> + struct page *page;
> +
> + BUILD_BUG_ON(sizeof(*vmx->ve_info) > PAGE_SIZE);
> + page = alloc_page(GFP_KERNEL_ACCOUNT | __GFP_ZERO);
> + if (page)
> + vmx->ve_info = page_to_virt(page);
> + }
> + if (vmx->ve_info) {
> + /*
> + * Allow #VE delivery. CPU sets this field to
> + * 0xFFFFFFFF on #VE delivery. Another #VE can
> + * occur only if software clears the field.
> + */
> + vmx->ve_info->delivery = 0;
> + vmcs_write64(VE_INFORMATION_ADDRESS,
> + __pa(vmx->ve_info));
> + } else {
> + /*
> + * Because SECONDARY_EXEC_EPT_VIOLATION_VE is
> + * used only when ept_violation_ve_test is true,
> + * it's okay to go with the bit disabled.
> + */
> + pr_err("Failed to allocate ve_info. disabling EPT_VIOLATION_VE.\n");
> + secondary_exec_controls_clearbit(
> + vmx, SECONDARY_EXEC_EPT_VIOLATION_VE);
> + }
> + }
> + }
>
> if (cpu_has_tertiary_exec_ctrls())
> tertiary_exec_controls_set(vmx, vmx_tertiary_exec_control(vmx));
> @@ -5116,7 +5162,14 @@ static int handle_exception_nmi(struct kvm_vcpu *vcpu)
> if (handle_guest_split_lock(kvm_rip_read(vcpu)))
> return 1;
> fallthrough;
> + case VE_VECTOR:
> default:
> + if (ept_violation_ve_test && ex_no == VE_VECTOR) {
> + pr_err("VMEXIT due to unexpected #VE.\n");
> + secondary_exec_controls_clearbit(
> + vmx, SECONDARY_EXEC_EPT_VIOLATION_VE);
> + return 1;
> + }
> kvm_run->exit_reason = KVM_EXIT_EXCEPTION;
> kvm_run->ex.exception = ex_no;
> kvm_run->ex.error_code = error_code;
> @@ -6182,6 +6235,17 @@ void dump_vmcs(struct kvm_vcpu *vcpu)
> if (secondary_exec_control & SECONDARY_EXEC_ENABLE_VPID)
> pr_err("Virtual processor ID = 0x%04x\n",
> vmcs_read16(VIRTUAL_PROCESSOR_ID));
> + if (secondary_exec_control & SECONDARY_EXEC_EPT_VIOLATION_VE) {
> + struct vmx_ve_information *ve_info;
> + pr_err("VE info address = 0x%016llx\n",
> + vmcs_read64(VE_INFORMATION_ADDRESS));
> + ve_info = __va(vmcs_read64(VE_INFORMATION_ADDRESS));
> + pr_err("ve_info: 0x%08x 0x%08x 0x%016llx 0x%016llx 0x%016llx 0x%04x\n",
> + ve_info->exit_reason, ve_info->delivery,
> + ve_info->exit_qualification,
> + ve_info->guest_linear_address,
> + ve_info->guest_physical_address, ve_info->eptp_index);
> + }
> }
>
> /*
> @@ -7173,6 +7237,8 @@ void vmx_vcpu_free(struct kvm_vcpu *vcpu)
> free_vpid(vmx->vpid);
> nested_vmx_free_vcpu(vcpu);
> free_loaded_vmcs(vmx->loaded_vmcs);
> + if (vmx->ve_info)
> + free_page((unsigned long)vmx->ve_info);
> }
>
> int vmx_vcpu_create(struct kvm_vcpu *vcpu)
> diff --git a/arch/x86/kvm/vmx/vmx.h b/arch/x86/kvm/vmx/vmx.h
> index 9feb994e5ea2..60d93c38e014 100644
> --- a/arch/x86/kvm/vmx/vmx.h
> +++ b/arch/x86/kvm/vmx/vmx.h
> @@ -338,6 +338,9 @@ struct vcpu_vmx {
> DECLARE_BITMAP(read, MAX_POSSIBLE_PASSTHROUGH_MSRS);
> DECLARE_BITMAP(write, MAX_POSSIBLE_PASSTHROUGH_MSRS);
> } shadow_msr_intercept;
> +
> + /* ve_info must be page aligned. */
> + struct vmx_ve_information *ve_info;
> };
>
> struct kvm_vmx {
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