linux-kernel - [PATCH 127/128] KVM: selftests: Trust that MAXPHYADDR > memslot0 in vmx_apic_access

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Date:   Wed,  4 May 2022 22:49:13 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Andrew Jones <drjones@...hat.com>,
        David Matlack <dmatlack@...gle.com>,
        Ben Gardon <bgardon@...gle.com>,
        Oliver Upton <oupton@...gle.com>,
        Sean Christopherson <seanjc@...gle.com>
Subject: [PATCH 127/128] KVM: selftests: Trust that MAXPHYADDR > memslot0 in vmx_apic_access_test

Use vm->max_gfn to compute the highest gpa in vmx_apic_access_test, and
blindly trust that the highest gfn/gpa will be well above the memory
carved out for memslot0.  The existing check is beyond paranoid; KVM
doesn't support CPUs with host.MAXPHYADDR < 32, and the selftests are all
kinds of hosed if memslot0 overlaps the local xAPIC, which resides above
"lower" (below 4gb) DRAM.

Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 .../testing/selftests/kvm/x86_64/vmx_apic_access_test.c  | 9 +--------
 1 file changed, 1 insertion(+), 8 deletions(-)

diff --git a/tools/testing/selftests/kvm/x86_64/vmx_apic_access_test.c b/tools/testing/selftests/kvm/x86_64/vmx_apic_access_test.c
index ef7514376b1e..ccb05ef7234e 100644
--- a/tools/testing/selftests/kvm/x86_64/vmx_apic_access_test.c
+++ b/tools/testing/selftests/kvm/x86_64/vmx_apic_access_test.c
@@ -72,8 +72,6 @@ static void l1_guest_code(struct vmx_pages *vmx_pages, unsigned long high_gpa)
 int main(int argc, char *argv[])
 {
 	unsigned long apic_access_addr = ~0ul;
-	unsigned int paddr_width;
-	unsigned int vaddr_width;
 	vm_vaddr_t vmx_pages_gva;
 	unsigned long high_gpa;
 	struct vmx_pages *vmx;
@@ -86,12 +84,7 @@ int main(int argc, char *argv[])
 
 	vm = vm_create_with_one_vcpu(&vcpu, l1_guest_code);
 
-	kvm_get_cpu_address_width(&paddr_width, &vaddr_width);
-	high_gpa = (1ul << paddr_width) - getpagesize();
-	if ((unsigned long)DEFAULT_GUEST_PHY_PAGES * getpagesize() > high_gpa) {
-		print_skip("No unbacked physical page available");
-		exit(KSFT_SKIP);
-	}
+	high_gpa = (vm->max_gfn - 1) << vm->page_shift;
 
 	vmx = vcpu_alloc_vmx(vm, &vmx_pages_gva);
 	prepare_virtualize_apic_accesses(vmx, vm);
-- 
2.36.0.464.gb9c8b46e94-goog