Commit be420222 authored by Linus Torvalds's avatar Linus Torvalds
Browse files

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
parents 5af5d43f 7ae15e2f

arch/x86/coco/tdx/tdx.c

+116 −22
Original line number Diff line number Diff line
@@ -78,6 +78,32 @@ static inline void tdcall(u64 fn, struct tdx_module_args *args) 
		panic("TDCALL %lld failed (Buggy TDX module!)\n", fn);

}



/* Read TD-scoped metadata */

static inline u64 tdg_vm_rd(u64 field, u64 *value)

{

	struct tdx_module_args args = {

		.rdx = field,

	};

	u64 ret;



	ret = __tdcall_ret(TDG_VM_RD, &args);

	*value = args.r8;



	return ret;

}



/* Write TD-scoped metadata */

static inline u64 tdg_vm_wr(u64 field, u64 value, u64 mask)

{

	struct tdx_module_args args = {

		.rdx = field,

		.r8 = value,

		.r9 = mask,

	};



	return __tdcall(TDG_VM_WR, &args);

}



/**

 * tdx_mcall_get_report0() - Wrapper to get TDREPORT0 (a.k.a. TDREPORT

 *                           subtype 0) using TDG.MR.REPORT TDCALL.
@@ -168,7 +194,87 @@ static void __noreturn tdx_panic(const char *msg) 
		__tdx_hypercall(&args);

}



static void tdx_parse_tdinfo(u64 *cc_mask)

/*

 * The kernel cannot handle #VEs when accessing normal kernel memory. Ensure

 * that no #VE will be delivered for accesses to TD-private memory.

 *

 * TDX 1.0 does not allow the guest to disable SEPT #VE on its own. The VMM

 * controls if the guest will receive such #VE with TD attribute

 * ATTR_SEPT_VE_DISABLE.

 *

 * Newer TDX modules allow the guest to control if it wants to receive SEPT

 * violation #VEs.

 *

 * Check if the feature is available and disable SEPT #VE if possible.

 *

 * If the TD is allowed to disable/enable SEPT #VEs, the ATTR_SEPT_VE_DISABLE

 * attribute is no longer reliable. It reflects the initial state of the

 * control for the TD, but it will not be updated if someone (e.g. bootloader)

 * changes it before the kernel starts. Kernel must check TDCS_TD_CTLS bit to

 * determine if SEPT #VEs are enabled or disabled.

 */

static void disable_sept_ve(u64 td_attr)

{

	const char *msg = "TD misconfiguration: SEPT #VE has to be disabled";

	bool debug = td_attr & ATTR_DEBUG;

	u64 config, controls;



	/* Is this TD allowed to disable SEPT #VE */

	tdg_vm_rd(TDCS_CONFIG_FLAGS, &config);

	if (!(config & TDCS_CONFIG_FLEXIBLE_PENDING_VE)) {

		/* No SEPT #VE controls for the guest: check the attribute */

		if (td_attr & ATTR_SEPT_VE_DISABLE)

			return;



		/* Relax SEPT_VE_DISABLE check for debug TD for backtraces */

		if (debug)

			pr_warn("%s\n", msg);

		else

			tdx_panic(msg);

		return;

	}



	/* Check if SEPT #VE has been disabled before us */

	tdg_vm_rd(TDCS_TD_CTLS, &controls);

	if (controls & TD_CTLS_PENDING_VE_DISABLE)

		return;



	/* Keep #VEs enabled for splats in debugging environments */

	if (debug)

		return;



	/* Disable SEPT #VEs */

	tdg_vm_wr(TDCS_TD_CTLS, TD_CTLS_PENDING_VE_DISABLE,

		  TD_CTLS_PENDING_VE_DISABLE);

}



/*

 * TDX 1.0 generates a #VE when accessing topology-related CPUID leafs (0xB and

 * 0x1F) and the X2APIC_APICID MSR. The kernel returns all zeros on CPUID #VEs.

 * In practice, this means that the kernel can only boot with a plain topology.

 * Any complications will cause problems.

 *

 * The ENUM_TOPOLOGY feature allows the VMM to provide topology information.

 * Enabling the feature  eliminates topology-related #VEs: the TDX module

 * virtualizes accesses to the CPUID leafs and the MSR.

 *

 * Enable ENUM_TOPOLOGY if it is available.

 */

static void enable_cpu_topology_enumeration(void)

{

	u64 configured;



	/* Has the VMM provided a valid topology configuration? */

	tdg_vm_rd(TDCS_TOPOLOGY_ENUM_CONFIGURED, &configured);

	if (!configured) {

		pr_err("VMM did not configure X2APIC_IDs properly\n");

		return;

	}



	tdg_vm_wr(TDCS_TD_CTLS, TD_CTLS_ENUM_TOPOLOGY, TD_CTLS_ENUM_TOPOLOGY);

}



static void tdx_setup(u64 *cc_mask)

{

	struct tdx_module_args args = {};

	unsigned int gpa_width;
@@ -193,21 +299,13 @@ static void tdx_parse_tdinfo(u64 *cc_mask) 
	gpa_width = args.rcx & GENMASK(5, 0);

	*cc_mask = BIT_ULL(gpa_width - 1);



	/*

	 * The kernel can not handle #VE's when accessing normal kernel

	 * memory.  Ensure that no #VE will be delivered for accesses to

	 * TD-private memory.  Only VMM-shared memory (MMIO) will #VE.

	 */

	td_attr = args.rdx;

	if (!(td_attr & ATTR_SEPT_VE_DISABLE)) {

		const char *msg = "TD misconfiguration: SEPT_VE_DISABLE attribute must be set.";



		/* Relax SEPT_VE_DISABLE check for debug TD. */

		if (td_attr & ATTR_DEBUG)

			pr_warn("%s\n", msg);

		else

			tdx_panic(msg);

	}

	/* Kernel does not use NOTIFY_ENABLES and does not need random #VEs */

	tdg_vm_wr(TDCS_NOTIFY_ENABLES, 0, -1ULL);



	disable_sept_ve(td_attr);

	enable_cpu_topology_enumeration();

}



/*
@@ -929,10 +1027,6 @@ static void tdx_kexec_finish(void) 


void __init tdx_early_init(void)

{

	struct tdx_module_args args = {

		.rdx = TDCS_NOTIFY_ENABLES,

		.r9 = -1ULL,

	};

	u64 cc_mask;

	u32 eax, sig[3];
@@ -947,11 +1041,11 @@ void __init tdx_early_init(void) 
	setup_force_cpu_cap(X86_FEATURE_TSC_RELIABLE);



	cc_vendor = CC_VENDOR_INTEL;

	tdx_parse_tdinfo(&cc_mask);

	cc_set_mask(cc_mask);



	/* Kernel does not use NOTIFY_ENABLES and does not need random #VEs */

	tdcall(TDG_VM_WR, &args);

	/* Configure the TD */

	tdx_setup(&cc_mask);



	cc_set_mask(cc_mask);



	/*

	 * All bits above GPA width are reserved and kernel treats shared bit

arch/x86/include/asm/shared/tdx.h

+12 −1
Original line number Diff line number Diff line
@@ -16,10 +16,21 @@ 
#define TDG_VP_VEINFO_GET		3

#define TDG_MR_REPORT			4

#define TDG_MEM_PAGE_ACCEPT		6

#define TDG_VM_RD			7

#define TDG_VM_WR			8



/* TDCS fields. To be used by TDG.VM.WR and TDG.VM.RD module calls */

/* TDX TD-Scope Metadata. To be used by TDG.VM.WR and TDG.VM.RD */

#define TDCS_CONFIG_FLAGS		0x1110000300000016

#define TDCS_TD_CTLS			0x1110000300000017

#define TDCS_NOTIFY_ENABLES		0x9100000000000010

#define TDCS_TOPOLOGY_ENUM_CONFIGURED	0x9100000000000019



/* TDCS_CONFIG_FLAGS bits */

#define TDCS_CONFIG_FLEXIBLE_PENDING_VE	BIT_ULL(1)



/* TDCS_TD_CTLS bits */

#define TD_CTLS_PENDING_VE_DISABLE	BIT_ULL(0)

#define TD_CTLS_ENUM_TOPOLOGY		BIT_ULL(1)



/* TDX hypercall Leaf IDs */

#define TDVMCALL_MAP_GPA		0x10001