path: root/arch/x86/kvm/cpuid.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * Kernel-based Virtual Machine driver for Linux
 * cpuid support routines
 *
 * derived from arch/x86/kvm/x86.c
 *
 * Copyright 2011 Red Hat, Inc. and/or its affiliates.
 * Copyright IBM Corporation, 2008
 */
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/kvm_host.h>
#include "linux/lockdep.h"
#include <linux/export.h>
#include <linux/vmalloc.h>
#include <linux/uaccess.h>
#include <linux/sched/stat.h>

#include <asm/processor.h>
#include <asm/user.h>
#include <asm/fpu/xstate.h>
#include <asm/sgx.h>
#include <asm/cpuid.h>
#include "cpuid.h"
#include "lapic.h"
#include "mmu.h"
#include "trace.h"
#include "pmu.h"
#include "xen.h"

/*
 * Unlike "struct cpuinfo_x86.x86_capability", kvm_cpu_caps doesn't need to be
 * aligned to sizeof(unsigned long) because it's not accessed via bitops.
 */
u32 kvm_cpu_caps[NR_KVM_CPU_CAPS] __read_mostly;
EXPORT_SYMBOL_GPL(kvm_cpu_caps);

u32 xstate_required_size(u64 xstate_bv, bool compacted)
{
	int feature_bit = 0;
	u32 ret = XSAVE_HDR_SIZE + XSAVE_HDR_OFFSET;

	xstate_bv &= XFEATURE_MASK_EXTEND;
	while (xstate_bv) {
		if (xstate_bv & 0x1) {
		        u32 eax, ebx, ecx, edx, offset;
		        cpuid_count(0xD, feature_bit, &eax, &ebx, &ecx, &edx);
			/* ECX[1]: 64B alignment in compacted form */
			if (compacted)
				offset = (ecx & 0x2) ? ALIGN(ret, 64) : ret;
			else
				offset = ebx;
			ret = max(ret, offset + eax);
		}

		xstate_bv >>= 1;
		feature_bit++;
	}

	return ret;
}

#define F feature_bit

/* Scattered Flag - For features that are scattered by cpufeatures.h. */
#define SF(name)						\
({								\
	BUILD_BUG_ON(X86_FEATURE_##name >= MAX_CPU_FEATURES);	\
	(boot_cpu_has(X86_FEATURE_##name) ? F(name) : 0);	\
})

/*
 * Magic value used by KVM when querying userspace-provided CPUID entries and
 * doesn't care about the CPIUD index because the index of the function in
 * question is not significant.  Note, this magic value must have at least one
 * bit set in bits[63:32] and must be consumed as a u64 by cpuid_entry2_find()
 * to avoid false positives when processing guest CPUID input.
 */
#define KVM_CPUID_INDEX_NOT_SIGNIFICANT -1ull

static inline struct kvm_cpuid_entry2 *cpuid_entry2_find(
	struct kvm_cpuid_entry2 *entries, int nent, u32 function, u64 index)
{
	struct kvm_cpuid_entry2 *e;
	int i;

	/*
	 * KVM has a semi-arbitrary rule that querying the guest's CPUID model
	 * with IRQs disabled is disallowed.  The CPUID model can legitimately
	 * have over one hundred entries, i.e. the lookup is slow, and IRQs are
	 * typically disabled in KVM only when KVM is in a performance critical
	 * path, e.g. the core VM-Enter/VM-Exit run loop.  Nothing will break
	 * if this rule is violated, this assertion is purely to flag potential
	 * performance issues.  If this fires, consider moving the lookup out
	 * of the hotpath, e.g. by caching information during CPUID updates.
	 */
	lockdep_assert_irqs_enabled();

	for (i = 0; i < nent; i++) {
		e = &entries[i];

		if (e->function != function)
			continue;

		/*
		 * If the index isn't significant, use the first entry with a
		 * matching function.  It's userspace's responsibility to not
		 * provide "duplicate" entries in all cases.
		 */
		if (!(e->flags & KVM_CPUID_FLAG_SIGNIFCANT_INDEX) || e->index == index)
			return e;


		/*
		 * Similarly, use the first matching entry if KVM is doing a
		 * lookup (as opposed to emulating CPUID) for a function that's
		 * architecturally defined as not having a significant index.
		 */
		if (index == KVM_CPUID_INDEX_NOT_SIGNIFICANT) {
			/*
			 * Direct lookups from KVM should not diverge from what
			 * KVM defines internally (the architectural behavior).
			 */
			WARN_ON_ONCE(cpuid_function_is_indexed(function));
			return e;
		}
	}

	return NULL;
}

static int kvm_check_cpuid(struct kvm_vcpu *vcpu,
			   struct kvm_cpuid_entry2 *entries,
			   int nent)
{
	struct kvm_cpuid_entry2 *best;
	u64 xfeatures;

	/*
	 * The existing code assumes virtual address is 48-bit or 57-bit in the
	 * canonical address checks; exit if it is ever changed.
	 */
	best = cpuid_entry2_find(entries, nent, 0x80000008,
				 KVM_CPUID_INDEX_NOT_SIGNIFICANT);
	if (best) {
		int vaddr_bits = (best->eax & 0xff00) >> 8;

		if (vaddr_bits != 48 && vaddr_bits != 57 && vaddr_bits != 0)
			return -EINVAL;
	}

	/*
	 * Exposing dynamic xfeatures to the guest requires additional
	 * enabling in the FPU, e.g. to expand the guest XSAVE state size.
	 */
	best = cpuid_entry2_find(entries, nent, 0xd, 0);
	if (!best)
		return 0;

	xfeatures = best->eax | ((u64)best->edx << 32);
	xfeatures &= XFEATURE_MASK_USER_DYNAMIC;
	if (!xfeatures)
		return 0;

	return fpu_enable_guest_xfd_features(&vcpu->arch.guest_fpu, xfeatures);
}

/* Check whether the supplied CPUID data is equal to what is already set for the vCPU. */
static int kvm_cpuid_check_equal(struct kvm_vcpu *vcpu, struct kvm_cpuid_entry2 *e2,
				 int nent)
{
	struct kvm_cpuid_entry2 *orig;
	int i;

	if (nent != vcpu->arch.cpuid_nent)
		return -EINVAL;

	for (i = 0; i < nent; i++) {
		orig = &vcpu->arch.cpuid_entries[i];
		if (e2[i].function