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- Add new infrastructure for reading TDX metadata
- Use the newly-available metadata to:
- Disable potentially nasty #VE exceptions
- Get more complete CPU topology information from the VMM
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Merge tag 'x86_tdx_for_6.13-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull tdx updates from Dave Hansen:
"These essentially refine some interactions between TDX guests and
VMMs.
The first leverages a new TDX module feature to runtime disable the
ability for a VM to inject #VE exceptions. Before this feature, there
was only a static on/off switch and the guest had to panic if it was
configured in a bad state.
The second lets the guest opt in to be able to access the topology
CPUID leaves. Before this, accesses to those leaves would #VE.
For both of these, it would have been nicest to just change the
default behavior, but some pesky "other" OSes evidently need to retain
the legacy behavior.
Summary:
- Add new infrastructure for reading TDX metadata
- Use the newly-available metadata to:
- Disable potentially nasty #VE exceptions
- Get more complete CPU topology information from the VMM"
* tag 'x86_tdx_for_6.13-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
x86/tdx: Enable CPU topology enumeration
x86/tdx: Dynamically disable SEPT violations from causing #VEs
x86/tdx: Rename tdx_parse_tdinfo() to tdx_setup()
x86/tdx: Introduce wrappers to read and write TD metadata
This commit is contained in:
Linus Torvalds
commit
be4202228e
@ -78,6 +78,32 @@ static inline void tdcall(u64 fn, struct tdx_module_args *args)
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panic("TDCALL %lld failed (Buggy TDX module!)\n", fn);
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}
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/* Read TD-scoped metadata */
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static inline u64 tdg_vm_rd(u64 field, u64 *value)
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{
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struct tdx_module_args args = {
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.rdx = field,
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};
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u64 ret;
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ret = __tdcall_ret(TDG_VM_RD, &args);
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*value = args.r8;
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return ret;
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}
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/* Write TD-scoped metadata */
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static inline u64 tdg_vm_wr(u64 field, u64 value, u64 mask)
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{
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struct tdx_module_args args = {
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.rdx = field,
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.r8 = value,
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.r9 = mask,
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};
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return __tdcall(TDG_VM_WR, &args);
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}
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/**
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* tdx_mcall_get_report0() - Wrapper to get TDREPORT0 (a.k.a. TDREPORT
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* subtype 0) using TDG.MR.REPORT TDCALL.
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@ -168,7 +194,87 @@ static void __noreturn tdx_panic(const char *msg)
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__tdx_hypercall(&args);
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}
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static void tdx_parse_tdinfo(u64 *cc_mask)
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/*
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* The kernel cannot handle #VEs when accessing normal kernel memory. Ensure
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* that no #VE will be delivered for accesses to TD-private memory.
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*
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* TDX 1.0 does not allow the guest to disable SEPT #VE on its own. The VMM
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* controls if the guest will receive such #VE with TD attribute
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* ATTR_SEPT_VE_DISABLE.
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*
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* Newer TDX modules allow the guest to control if it wants to receive SEPT
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* violation #VEs.
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*
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* Check if the feature is available and disable SEPT #VE if possible.
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*
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* If the TD is allowed to disable/enable SEPT #VEs, the ATTR_SEPT_VE_DISABLE
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* attribute is no longer reliable. It reflects the initial state of the
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* control for the TD, but it will not be updated if someone (e.g. bootloader)
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* changes it before the kernel starts. Kernel must check TDCS_TD_CTLS bit to
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* determine if SEPT #VEs are enabled or disabled.
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*/
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static void disable_sept_ve(u64 td_attr)
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{
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const char *msg = "TD misconfiguration: SEPT #VE has to be disabled";
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bool debug = td_attr & ATTR_DEBUG;
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u64 config, controls;
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/* Is this TD allowed to disable SEPT #VE */
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tdg_vm_rd(TDCS_CONFIG_FLAGS, &config);
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if (!(config & TDCS_CONFIG_FLEXIBLE_PENDING_VE)) {
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/* No SEPT #VE controls for the guest: check the attribute */
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if (td_attr & ATTR_SEPT_VE_DISABLE)
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return;
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/* Relax SEPT_VE_DISABLE check for debug TD for backtraces */
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if (debug)
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pr_warn("%s\n", msg);
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else
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tdx_panic(msg);
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return;
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}
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/* Check if SEPT #VE has been disabled before us */
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tdg_vm_rd(TDCS_TD_CTLS, &controls);
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if (controls & TD_CTLS_PENDING_VE_DISABLE)
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return;
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/* Keep #VEs enabled for splats in debugging environments */
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if (debug)
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return;
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/* Disable SEPT #VEs */
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tdg_vm_wr(TDCS_TD_CTLS, TD_CTLS_PENDING_VE_DISABLE,
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TD_CTLS_PENDING_VE_DISABLE);
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}
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/*
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* TDX 1.0 generates a #VE when accessing topology-related CPUID leafs (0xB and
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* 0x1F) and the X2APIC_APICID MSR. The kernel returns all zeros on CPUID #VEs.
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* In practice, this means that the kernel can only boot with a plain topology.
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* Any complications will cause problems.
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*
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* The ENUM_TOPOLOGY feature allows the VMM to provide topology information.
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* Enabling the feature eliminates topology-related #VEs: the TDX module
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* virtualizes accesses to the CPUID leafs and the MSR.
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*
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* Enable ENUM_TOPOLOGY if it is available.
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*/
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static void enable_cpu_topology_enumeration(void)
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{
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u64 configured;
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/* Has the VMM provided a valid topology configuration? */
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tdg_vm_rd(TDCS_TOPOLOGY_ENUM_CONFIGURED, &configured);
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if (!configured) {
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pr_err("VMM did not configure X2APIC_IDs properly\n");
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return;
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}
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tdg_vm_wr(TDCS_TD_CTLS, TD_CTLS_ENUM_TOPOLOGY, TD_CTLS_ENUM_TOPOLOGY);
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}
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static void tdx_setup(u64 *cc_mask)
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{
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struct tdx_module_args args = {};
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unsigned int gpa_width;
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@ -193,21 +299,13 @@ static void tdx_parse_tdinfo(u64 *cc_mask)
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gpa_width = args.rcx & GENMASK(5, 0);
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*cc_mask = BIT_ULL(gpa_width - 1);
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/*
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* The kernel can not handle #VE's when accessing normal kernel
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* memory. Ensure that no #VE will be delivered for accesses to
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* TD-private memory. Only VMM-shared memory (MMIO) will #VE.
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*/
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td_attr = args.rdx;
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if (!(td_attr & ATTR_SEPT_VE_DISABLE)) {
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const char *msg = "TD misconfiguration: SEPT_VE_DISABLE attribute must be set.";
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/* Relax SEPT_VE_DISABLE check for debug TD. */
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if (td_attr & ATTR_DEBUG)
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pr_warn("%s\n", msg);
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else
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tdx_panic(msg);
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}
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/* Kernel does not use NOTIFY_ENABLES and does not need random #VEs */
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tdg_vm_wr(TDCS_NOTIFY_ENABLES, 0, -1ULL);
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disable_sept_ve(td_attr);
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enable_cpu_topology_enumeration();
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}
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/*
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@ -929,10 +1027,6 @@ static void tdx_kexec_finish(void)
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void __init tdx_early_init(void)
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{
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struct tdx_module_args args = {
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.rdx = TDCS_NOTIFY_ENABLES,
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.r9 = -1ULL,
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};
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u64 cc_mask;
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u32 eax, sig[3];
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@ -947,11 +1041,11 @@ void __init tdx_early_init(void)
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setup_force_cpu_cap(X86_FEATURE_TSC_RELIABLE);
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cc_vendor = CC_VENDOR_INTEL;
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tdx_parse_tdinfo(&cc_mask);
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cc_set_mask(cc_mask);
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/* Kernel does not use NOTIFY_ENABLES and does not need random #VEs */
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tdcall(TDG_VM_WR, &args);
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/* Configure the TD */
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tdx_setup(&cc_mask);
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cc_set_mask(cc_mask);
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/*
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* All bits above GPA width are reserved and kernel treats shared bit
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@ -16,10 +16,21 @@
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#define TDG_VP_VEINFO_GET 3
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#define TDG_MR_REPORT 4
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#define TDG_MEM_PAGE_ACCEPT 6
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#define TDG_VM_RD 7
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#define TDG_VM_WR 8
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/* TDCS fields. To be used by TDG.VM.WR and TDG.VM.RD module calls */
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/* TDX TD-Scope Metadata. To be used by TDG.VM.WR and TDG.VM.RD */
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#define TDCS_CONFIG_FLAGS 0x1110000300000016
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#define TDCS_TD_CTLS 0x1110000300000017
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#define TDCS_NOTIFY_ENABLES 0x9100000000000010
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#define TDCS_TOPOLOGY_ENUM_CONFIGURED 0x9100000000000019
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/* TDCS_CONFIG_FLAGS bits */
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#define TDCS_CONFIG_FLEXIBLE_PENDING_VE BIT_ULL(1)
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/* TDCS_TD_CTLS bits */
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#define TD_CTLS_PENDING_VE_DISABLE BIT_ULL(0)
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#define TD_CTLS_ENUM_TOPOLOGY BIT_ULL(1)
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/* TDX hypercall Leaf IDs */
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#define TDVMCALL_MAP_GPA 0x10001
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