On 8/5/21 11:54 AM, Paolo Bonzini wrote: > Accessing guest physical addresses at 0xFFFD_0000_0000 and above causes > a failure on AMD processors because those addresses are reserved by > HyperTransport (this is not documented). Oh, but it's actually documented in the AMD IOMMU manual [0] (and AMD IOMMU in linux do mark it as a reserved IOVA region i.e. HT_RANGE_START..HT_RANGE_END). And it's usually marked as a reserved type in E820. At least on the machines I've seen. See manual section '2.1.2 IOMMU Logical Topology': "Special address controls in Table 3 are interpreted against untranslated guest physical addressess (GPA) that lack a PASID TLP prefix." Base Address Top Address Use FD_0000_0000h FD_F7FF_FFFFh Reserved interrupt address space FD_F800_0000h FD_F8FF_FFFFh Interrupt/EOI IntCtl FD_F900_0000h FD_F90F_FFFFh Legacy PIC IACK FD_F910_0000h FD_F91F_FFFFh System Management FD_F920_0000h FD_FAFF_FFFFh Reserved Page Tables FD_FB00_0000h FD_FBFF_FFFFh Address Translation FD_FC00_0000h FD_FDFF_FFFFh I/O Space FD_FE00_0000h FD_FFFF_FFFFh Configuration FE_0000_0000h FE_1FFF_FFFFh Extended Configuration/Device Messages FE_2000_0000h FF_FFFF_FFFFh Reserved It covers the range starting that address you fixed up ... up to 1Tb, fwiw. You mark it ~1010G as max gfn so shouldn't be a problem. [0] https://www.amd.com/system/files/TechDocs/48882_IOMMU.pdf > Avoid selftests failures > by reserving those guest physical addresses. > > Fixes: ef4c9f4f6546 ("KVM: selftests: Fix 32-bit truncation of vm_get_max_gfn()") > Cc: stable@xxxxxxxxxxxxxxx > Cc: David Matlack <dmatlack@xxxxxxxxxx> > Reported-by: Maxim Levitsky <mlevitsk@xxxxxxxxxx> > Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx> > --- > tools/testing/selftests/kvm/lib/kvm_util.c | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c b/tools/testing/selftests/kvm/lib/kvm_util.c > index 10a8ed691c66..d995cc9836ee 100644 > --- a/tools/testing/selftests/kvm/lib/kvm_util.c > +++ b/tools/testing/selftests/kvm/lib/kvm_util.c > @@ -309,6 +309,12 @@ struct kvm_vm *vm_create(enum vm_guest_mode mode, uint64_t phy_pages, int perm) > /* Limit physical addresses to PA-bits. */ > vm->max_gfn = ((1ULL << vm->pa_bits) >> vm->page_shift) - 1; > > +#ifdef __x86_64__ > + /* Avoid reserved HyperTransport region on AMD processors. */ > + if (vm->pa_bits == 48) > + vm->max_gfn = 0xfffcfffff; > +#endif > + Not sure if it's worth the trouble having a macro with the same name as AMD iommu like: #define HT_RANGE_START (0xfd00000000ULL) #define MAX_GFN (HT_RANGE_START - 1ULL) #ifdef __x86_64__ /* Avoid reserved HyperTransport region on AMD processors. */ if (vm->pa_bits == 48) vm->max_gfn = MAX_GFN; #endif It's a detail, but *perhaps* would help people grepping around it. Also, not sure if checking against AMD cpuid vendor is worth, considering this is a limitation only on AMD. > /* Allocate and setup memory for guest. */ > vm->vpages_mapped = sparsebit_alloc(); > if (phy_pages != 0) >
