[PATCH 5.15 087/171] selftests: KVM: avoid failures due to reserved HyperTransport region

Greg Kroah-Hartman
2021-12-13T10:16:50Z

From: Paolo Bonzini <pbonzini@redhat.com>

commit c8cc43c1eae2910ac96daa4216e0fb3391ad0504 upstream.

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: ef4c9f4f6546 ("KVM: selftests: Fix 32-bit truncation of vm_get_max_gfn()")
Cc: stable@vger.kernel.org
Cc: David Matlack <dmatlack@google.com>
Reported-by: Maxim Levitsky <mlevitsk@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20210805105423.412878-1-pbonzini@redhat.com>
Reviewed-by: Sean Christopherson <seanjc@google.com>
Tested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
tools/testing/selftests/kvm/include/kvm_util.h | 9 ++
tools/testing/selftests/kvm/lib/kvm_util.c | 2
tools/testing/selftests/kvm/lib/x86_64/processor.c | 68 +++++++++++++++++++++
3 files changed, 78 insertions(+), 1 deletion(-)

--- a/tools/testing/selftests/kvm/include/kvm_util.h
+++ b/tools/testing/selftests/kvm/include/kvm_util.h
@@ -69,6 +69,15 @@ 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)

--- a/tools/testing/selftests/kvm/lib/kvm_util.c
+++ b/tools/testing/selftests/kvm/lib/kvm_util.c
@@ -307,7 +307,7 @@ struct kvm_vm *vm_create(enum vm_guest_m
(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();
--- a/tools/testing/selftests/kvm/lib/x86_64/processor.c
+++ b/tools/testing/selftests/kvm/lib/x86_64/processor.c
@@ -1433,3 +1433,71 @@ struct kvm_cpuid2 *vcpu_get_supported_hv

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);
+}