>From 9fc3309dbdf202e2bfaf7c79cbb608232d34e480 Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Mon, 29 Dec 2025 12:23:30 -0800 Subject: [PATCH 4/4] KVM: selftests: Verify TILELOADD actually #NM faults when XFD[18]=1 Rework the AMX test's #NM handling to use kvm_asm_safe() to verify an #NM actually occurs. As is, a completely missing #NM could go unnoticed. Signed-off-by: Sean Christopherson --- tools/testing/selftests/kvm/x86/amx_test.c | 29 ++++++++++++++-------- 1 file changed, 18 insertions(+), 11 deletions(-) diff --git a/tools/testing/selftests/kvm/x86/amx_test.c b/tools/testing/selftests/kvm/x86/amx_test.c index 1d5fffddc625..09c0e3440f0e 100644 --- a/tools/testing/selftests/kvm/x86/amx_test.c +++ b/tools/testing/selftests/kvm/x86/amx_test.c @@ -69,6 +69,12 @@ static inline void __tileloadd(void *tile) : : "a"(tile), "d"(0)); } +static inline int tileloadd_safe(void *tile) +{ + return kvm_asm_safe(".byte 0xc4,0xe2,0x7b,0x4b,0x04,0x10", + "a"(tile), "d"(0)); +} + static inline void __tilerelease(void) { asm volatile(".byte 0xc4, 0xe2, 0x78, 0x49, 0xc0" ::); @@ -137,6 +143,8 @@ static void __attribute__((__flatten__)) guest_code(struct tile_config *amx_cfg, struct tile_data *tiledata, struct xstate *xstate) { + int vector; + GUEST_ASSERT(this_cpu_has(X86_FEATURE_XSAVE) && this_cpu_has(X86_FEATURE_OSXSAVE)); check_xtile_info(); @@ -193,16 +201,13 @@ static void __attribute__((__flatten__)) guest_code(struct tile_config *amx_cfg, __tilerelease(); set_tilecfg(amx_cfg); __ldtilecfg(amx_cfg); - /* Trigger #NM exception */ - __tileloadd(tiledata); - GUEST_SYNC(AMX_SYNC_SAVE_RESTORE | AMX_SYNC_CHECK_TILEDATA); - GUEST_DONE(); -} + /* Verify TILELOADD gets #NM when XTILE_DATA is disabled via XFD. */ + vector = tileloadd_safe(tiledata); + __GUEST_ASSERT(vector == NM_VECTOR, + "Wanted #NM on tileloadd with XFD[18]=1, got %s", + ex_str(vector)); -void guest_nm_handler(struct ex_regs *regs) -{ - /* Check if #NM is triggered by XFEATURE_MASK_XTILE_DATA */ GUEST_SYNC(AMX_SYNC_SAVE_RESTORE); GUEST_ASSERT(!(get_cr0() & X86_CR0_TS)); GUEST_ASSERT(rdmsr(MSR_IA32_XFD_ERR) == XFEATURE_MASK_XTILE_DATA); @@ -215,6 +220,11 @@ void guest_nm_handler(struct ex_regs *regs) /* xfd=0, enable amx */ wrmsr(MSR_IA32_XFD, 0); GUEST_SYNC(AMX_SYNC_SAVE_RESTORE); + + __tileloadd(tiledata); + GUEST_SYNC(AMX_SYNC_SAVE_RESTORE | AMX_SYNC_CHECK_TILEDATA); + + GUEST_DONE(); } int main(int argc, char *argv[]) @@ -250,9 +260,6 @@ int main(int argc, char *argv[]) vcpu_regs_get(vcpu, ®s1); - /* Register #NM handler */ - vm_install_exception_handler(vm, NM_VECTOR, guest_nm_handler); - /* amx cfg for guest_code */ amx_cfg = vm_vaddr_alloc_page(vm); memset(addr_gva2hva(vm, amx_cfg), 0x0, getpagesize()); -- 2.52.0.351.gbe84eed79e-goog