From: Ricardo Koller Date: Fri, 11 Jun 2021 01:10:16 +0000 (-0700) Subject: KVM: selftests: Complete x86_64/sync_regs_test ucall X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=b7326c01122683b88e273a0cc826cd4c01234470;p=linux.git KVM: selftests: Complete x86_64/sync_regs_test ucall The guest in sync_regs_test does raw ucalls by directly accessing the ucall IO port. It makes these ucalls without setting %rdi to a `struct ucall`, which is what a ucall uses to pass messages. The issue is that if the host did a get_ucall (the receiver side), it would try to access the `struct ucall` at %rdi=0 which would lead to an error ("No mapping for vm virtual address, gva: 0x0"). This issue is currently benign as there is no get_ucall in sync_regs_test; however, that will change in the next commit as it changes the unhandled exception reporting mechanism to use ucalls. In that case, every vcpu_run is followed by a get_ucall to check if the guest is trying to report an unhandled exception. Fix this in advance by setting %rdi to a UCALL_NONE struct ucall for the sync_regs_test guest. Tested with gcc-[8,9,10], and clang-[9,11]. Signed-off-by: Ricardo Koller Reviewed-by: Andrew Jones Signed-off-by: Marc Zyngier Link: https://lore.kernel.org/r/20210611011020.3420067-3-ricarkol@google.com --- diff --git a/tools/testing/selftests/kvm/x86_64/sync_regs_test.c b/tools/testing/selftests/kvm/x86_64/sync_regs_test.c index d672f0a473f87..fc03a150278d0 100644 --- a/tools/testing/selftests/kvm/x86_64/sync_regs_test.c +++ b/tools/testing/selftests/kvm/x86_64/sync_regs_test.c @@ -24,6 +24,10 @@ #define UCALL_PIO_PORT ((uint16_t)0x1000) +struct ucall uc_none = { + .cmd = UCALL_NONE, +}; + /* * ucall is embedded here to protect against compiler reshuffling registers * before calling a function. In this test we only need to get KVM_EXIT_IO @@ -34,7 +38,8 @@ void guest_code(void) asm volatile("1: in %[port], %%al\n" "add $0x1, %%rbx\n" "jmp 1b" - : : [port] "d" (UCALL_PIO_PORT) : "rax", "rbx"); + : : [port] "d" (UCALL_PIO_PORT), "D" (&uc_none) + : "rax", "rbx"); } static void compare_regs(struct kvm_regs *left, struct kvm_regs *right)