Commit c8cc43c1 authored by Paolo Bonzini's avatar Paolo Bonzini
Browse files

selftests: KVM: avoid failures due to reserved HyperTransport region 



AMD proceessors define an address range that is reserved by HyperTransport
and causes a failure if used for guest physical addresses.  Avoid
selftests failures by reserving those guest physical addresses; the
rules are:

- On parts with <40 bits, its fully hidden from software.

- Before Fam17h, it was always 12G just below 1T, even if there was more
RAM above this location.  In this case we just not use any RAM above 1T.

- On Fam17h and later, it is variable based on SME, and is either just
below 2^48 (no encryption) or 2^43 (encryption).

Fixes: ef4c9f4f ("KVM: selftests: Fix 32-bit truncation of vm_get_max_gfn()")
Cc: stable@vger.kernel.org
Cc: David Matlack <dmatlack@google.com>
Reported-by: default avatarMaxim Levitsky <mlevitsk@redhat.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
Message-Id: <20210805105423.412878-1-pbonzini@redhat.com>
Reviewed-by: default avatarSean Christopherson <seanjc@google.com>
Tested-by: default avatarSean Christopherson <seanjc@google.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 3244867a

tools/testing/selftests/kvm/include/kvm_util.h

+9 −0
Original line number Diff line number Diff line
@@ -71,6 +71,15 @@ enum vm_guest_mode { 


#endif



#if defined(__x86_64__)

unsigned long vm_compute_max_gfn(struct kvm_vm *vm);

#else

static inline unsigned long vm_compute_max_gfn(struct kvm_vm *vm)

{

	return ((1ULL << vm->pa_bits) >> vm->page_shift) - 1;

}

#endif



#define MIN_PAGE_SIZE		(1U << MIN_PAGE_SHIFT)

#define PTES_PER_MIN_PAGE	ptes_per_page(MIN_PAGE_SIZE)

tools/testing/selftests/kvm/lib/kvm_util.c

+1 −1
Original line number Diff line number Diff line
@@ -302,7 +302,7 @@ struct kvm_vm *vm_create(enum vm_guest_mode mode, uint64_t phy_pages, int perm) 
		(1ULL << (vm->va_bits - 1)) >> vm->page_shift);



	/* Limit physical addresses to PA-bits. */

	vm->max_gfn = ((1ULL << vm->pa_bits) >> vm->page_shift) - 1;

	vm->max_gfn = vm_compute_max_gfn(vm);



	/* Allocate and setup memory for guest. */

	vm->vpages_mapped = sparsebit_alloc();

tools/testing/selftests/kvm/lib/x86_64/processor.c

+68 −0
Original line number Diff line number Diff line
@@ -1431,3 +1431,71 @@ struct kvm_cpuid2 *vcpu_get_supported_hv_cpuid(struct kvm_vm *vm, uint32_t vcpui 


	return cpuid;

}



#define X86EMUL_CPUID_VENDOR_AuthenticAMD_ebx 0x68747541

#define X86EMUL_CPUID_VENDOR_AuthenticAMD_ecx 0x444d4163

#define X86EMUL_CPUID_VENDOR_AuthenticAMD_edx 0x69746e65



static inline unsigned x86_family(unsigned int eax)

{

        unsigned int x86;



        x86 = (eax >> 8) & 0xf;



        if (x86 == 0xf)

                x86 += (eax >> 20) & 0xff;



        return x86;

}



unsigned long vm_compute_max_gfn(struct kvm_vm *vm)

{

	const unsigned long num_ht_pages = 12 << (30 - vm->page_shift); /* 12 GiB */

	unsigned long ht_gfn, max_gfn, max_pfn;

	uint32_t eax, ebx, ecx, edx, max_ext_leaf;



	max_gfn = (1ULL << (vm->pa_bits - vm->page_shift)) - 1;



	/* Avoid reserved HyperTransport region on AMD processors.  */

	eax = ecx = 0;

	cpuid(&eax, &ebx, &ecx, &edx);

	if (ebx != X86EMUL_CPUID_VENDOR_AuthenticAMD_ebx ||

	    ecx != X86EMUL_CPUID_VENDOR_AuthenticAMD_ecx ||

	    edx != X86EMUL_CPUID_VENDOR_AuthenticAMD_edx)

		return max_gfn;



	/* On parts with <40 physical address bits, the area is fully hidden */

	if (vm->pa_bits < 40)

		return max_gfn;



	/* Before family 17h, the HyperTransport area is just below 1T.  */

	ht_gfn = (1 << 28) - num_ht_pages;

	eax = 1;

	cpuid(&eax, &ebx, &ecx, &edx);

	if (x86_family(eax) < 0x17)

		goto done;



	/*

	 * Otherwise it's at the top of the physical address space, possibly

	 * reduced due to SME by bits 11:6 of CPUID[0x8000001f].EBX.  Use

	 * the old conservative value if MAXPHYADDR is not enumerated.

	 */

	eax = 0x80000000;

	cpuid(&eax, &ebx, &ecx, &edx);

	max_ext_leaf = eax;

	if (max_ext_leaf < 0x80000008)

		goto done;



	eax = 0x80000008;

	cpuid(&eax, &ebx, &ecx, &edx);

	max_pfn = (1ULL << ((eax & 0xff) - vm->page_shift)) - 1;

	if (max_ext_leaf >= 0x8000001f) {

		eax = 0x8000001f;

		cpuid(&eax, &ebx, &ecx, &edx);

		max_pfn >>= (ebx >> 6) & 0x3f;

	}



	ht_gfn = max_pfn - num_ht_pages;

done:

	return min(max_gfn, ht_gfn - 1);

}