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: 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>

diff --git a/tools/testing/selftests/kvm/include/kvm_util.h b/tools/testing/selftests/kvm/include/kvm_util.h
index 6a1a37f30494b327e36c8b54ec9ddd8a6d0996bc..da2b702da71a4320d59f87f1df4ba34147123e0e 100644 (file)
--- a/tools/testing/selftests/kvm/include/kvm_util.h
+++ b/tools/testing/selftests/kvm/include/kvm_util.h
@@ -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)
 

diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c b/tools/testing/selftests/kvm/lib/kvm_util.c
index 8f2e0bb1ef96a4f2103fc89c94a13bde34f09f4a..daf6fdb217a7649a80949b46ae31eb6eb93e6160 100644 (file)
--- a/tools/testing/selftests/kvm/lib/kvm_util.c
+++ b/tools/testing/selftests/kvm/lib/kvm_util.c
@@ -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();

diff --git a/tools/testing/selftests/kvm/lib/x86_64/processor.c b/tools/testing/selftests/kvm/lib/x86_64/processor.c
index 82c39db913699949648974ecb3530bad60431bea..eef7b34756d5ce40dbc2d6ea8751971245b2cfec 100644 (file)
--- a/tools/testing/selftests/kvm/lib/x86_64/processor.c
+++ b/tools/testing/selftests/kvm/lib/x86_64/processor.c
@@ -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);
+}