From 2d0f2a648147d6bbf0655e03500586a6712a7281 Mon Sep 17 00:00:00 2001 From: Maxim Levitsky Date: Fri, 4 Oct 2024 18:01:53 -0400 Subject: [PATCH 1/6] KVM: selftests: memslot_perf_test: increase guest sync timeout When memslot_perf_test is run nested, first iteration of test_memslot_rw_loop testcase, sometimes takes more than 2 seconds due to build of shadow page tables. Following iterations are fast. To be on the safe side, bump the timeout to 10 seconds. Signed-off-by: Maxim Levitsky Tested-by: Liam Merwick Reviewed-by: Liam Merwick Link: https://lore.kernel.org/r/20241004220153.287459-1-mlevitsk@redhat.com Signed-off-by: Sean Christopherson --- tools/testing/selftests/kvm/memslot_perf_test.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/tools/testing/selftests/kvm/memslot_perf_test.c b/tools/testing/selftests/kvm/memslot_perf_test.c index 989ffe0d047f..e3711beff7f3 100644 --- a/tools/testing/selftests/kvm/memslot_perf_test.c +++ b/tools/testing/selftests/kvm/memslot_perf_test.c @@ -417,7 +417,7 @@ static bool _guest_should_exit(void) */ static noinline void host_perform_sync(struct sync_area *sync) { - alarm(2); + alarm(10); atomic_store_explicit(&sync->sync_flag, true, memory_order_release); while (atomic_load_explicit(&sync->sync_flag, memory_order_acquire)) From 945bdae20be5a13f1fcdcb14ec356dcbeee35839 Mon Sep 17 00:00:00 2001 From: Patrick Roy Date: Thu, 24 Oct 2024 10:59:53 +0100 Subject: [PATCH 2/6] KVM: selftests: fix unintentional noop test in guest_memfd_test.c The loop in test_create_guest_memfd_invalid() that is supposed to test that nothing is accepted as a valid flag to KVM_CREATE_GUEST_MEMFD was initializing `flag` as 0 instead of BIT(0). This caused the loop to immediately exit instead of iterating over BIT(0), BIT(1), ... . Fixes: 8a89efd43423 ("KVM: selftests: Add basic selftest for guest_memfd()") Signed-off-by: Patrick Roy Reviewed-by: James Gowans Reviewed-by: Muhammad Usama Anjum Link: https://lore.kernel.org/r/20241024095956.3668818-1-roypat@amazon.co.uk Signed-off-by: Sean Christopherson --- tools/testing/selftests/kvm/guest_memfd_test.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/tools/testing/selftests/kvm/guest_memfd_test.c b/tools/testing/selftests/kvm/guest_memfd_test.c index ba0c8e996035..ce687f8d248f 100644 --- a/tools/testing/selftests/kvm/guest_memfd_test.c +++ b/tools/testing/selftests/kvm/guest_memfd_test.c @@ -134,7 +134,7 @@ static void test_create_guest_memfd_invalid(struct kvm_vm *vm) size); } - for (flag = 0; flag; flag <<= 1) { + for (flag = BIT(0); flag; flag <<= 1) { fd = __vm_create_guest_memfd(vm, page_size, flag); TEST_ASSERT(fd == -1 && errno == EINVAL, "guest_memfd() with flag '0x%lx' should fail with EINVAL", From 5b188cc4866aaf712e896f92ac42c7802135e507 Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Wed, 9 Oct 2024 08:49:41 -0700 Subject: [PATCH 3/6] KVM: selftests: Disable strict aliasing Disable strict aliasing, as has been done in the kernel proper for decades (literally since before git history) to fix issues where gcc will optimize away loads in code that looks 100% correct, but is _technically_ undefined behavior, and thus can be thrown away by the compiler. E.g. arm64's vPMU counter access test casts a uint64_t (unsigned long) pointer to a u64 (unsigned long long) pointer when setting PMCR.N via u64p_replace_bits(), which gcc-13 detects and optimizes away, i.e. ignores the result and uses the original PMCR. The issue is most easily observed by making set_pmcr_n() noinline and wrapping the call with printf(), e.g. sans comments, for this code: printf("orig = %lx, next = %lx, want = %lu\n", pmcr_orig, pmcr, pmcr_n); set_pmcr_n(&pmcr, pmcr_n); printf("orig = %lx, next = %lx, want = %lu\n", pmcr_orig, pmcr, pmcr_n); gcc-13 generates: 0000000000401c90 : 401c90: f9400002 ldr x2, [x0] 401c94: b3751022 bfi x2, x1, #11, #5 401c98: f9000002 str x2, [x0] 401c9c: d65f03c0 ret 0000000000402660 : 402724: aa1403e3 mov x3, x20 402728: aa1503e2 mov x2, x21 40272c: aa1603e0 mov x0, x22 402730: aa1503e1 mov x1, x21 402734: 940060ff bl 41ab30 <_IO_printf> 402738: aa1403e1 mov x1, x20 40273c: 910183e0 add x0, sp, #0x60 402740: 97fffd54 bl 401c90 402744: aa1403e3 mov x3, x20 402748: aa1503e2 mov x2, x21 40274c: aa1503e1 mov x1, x21 402750: aa1603e0 mov x0, x22 402754: 940060f7 bl 41ab30 <_IO_printf> with the value stored in [sp + 0x60] ignored by both printf() above and in the test proper, resulting in a false failure due to vcpu_set_reg() simply storing the original value, not the intended value. $ ./vpmu_counter_access Random seed: 0x6b8b4567 orig = 3040, next = 3040, want = 0 orig = 3040, next = 3040, want = 0 ==== Test Assertion Failure ==== aarch64/vpmu_counter_access.c:505: pmcr_n == get_pmcr_n(pmcr) pid=71578 tid=71578 errno=9 - Bad file descriptor 1 0x400673: run_access_test at vpmu_counter_access.c:522 2 (inlined by) main at vpmu_counter_access.c:643 3 0x4132d7: __libc_start_call_main at libc-start.o:0 4 0x413653: __libc_start_main at ??:0 5 0x40106f: _start at ??:0 Failed to update PMCR.N to 0 (received: 6) Somewhat bizarrely, gcc-11 also exhibits the same behavior, but only if set_pmcr_n() is marked noinline, whereas gcc-13 fails even if set_pmcr_n() is inlined in its sole caller. Cc: stable@vger.kernel.org Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116912 Signed-off-by: Sean Christopherson --- tools/testing/selftests/kvm/Makefile | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/tools/testing/selftests/kvm/Makefile b/tools/testing/selftests/kvm/Makefile index 156fbfae940f..1896ef383cae 100644 --- a/tools/testing/selftests/kvm/Makefile +++ b/tools/testing/selftests/kvm/Makefile @@ -241,10 +241,10 @@ CFLAGS += -Wall -Wstrict-prototypes -Wuninitialized -O2 -g -std=gnu99 \ -Wno-gnu-variable-sized-type-not-at-end -MD -MP -DCONFIG_64BIT \ -fno-builtin-memcmp -fno-builtin-memcpy \ -fno-builtin-memset -fno-builtin-strnlen \ - -fno-stack-protector -fno-PIE -I$(LINUX_TOOL_INCLUDE) \ - -I$(LINUX_TOOL_ARCH_INCLUDE) -I$(LINUX_HDR_PATH) -Iinclude \ - -I$( Date: Wed, 30 Oct 2024 21:53:33 -0700 Subject: [PATCH 4/6] KVM: selftests: Don't force -march=x86-64-v2 if it's unsupported Force -march=x86-64-v2 to avoid SSE/AVX instructions if and only if the uarch definition is supported by the compiler, e.g. gcc 7.5 only supports x86-64. Fixes: 9a400068a158 ("KVM: selftests: x86: Avoid using SSE/AVX instructions") Cc: Vitaly Kuznetsov Reviewed-and-tested-by: Vitaly Kuznetsov Link: https://lore.kernel.org/r/20241031045333.1209195-1-seanjc@google.com Signed-off-by: Sean Christopherson --- tools/testing/selftests/kvm/Makefile | 2 ++ 1 file changed, 2 insertions(+) diff --git a/tools/testing/selftests/kvm/Makefile b/tools/testing/selftests/kvm/Makefile index 1896ef383cae..48645a2e29da 100644 --- a/tools/testing/selftests/kvm/Makefile +++ b/tools/testing/selftests/kvm/Makefile @@ -249,8 +249,10 @@ ifeq ($(ARCH),s390) CFLAGS += -march=z10 endif ifeq ($(ARCH),x86) +ifeq ($(shell echo "void foo(void) { }" | $(CC) -march=x86-64-v2 -x c - -c -o /dev/null 2>/dev/null; echo "$$?"),0) CFLAGS += -march=x86-64-v2 endif +endif ifeq ($(ARCH),arm64) tools_dir := $(top_srcdir)/tools arm64_tools_dir := $(tools_dir)/arch/arm64/tools/ From 2657b82a78f18528bef56dc1b017158490970873 Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Thu, 31 Oct 2024 13:20:11 -0700 Subject: [PATCH 5/6] KVM: nVMX: Treat vpid01 as current if L2 is active, but with VPID disabled When getting the current VPID, e.g. to emulate a guest TLB flush, return vpid01 if L2 is running but with VPID disabled, i.e. if VPID is disabled in vmcs12. Architecturally, if VPID is disabled, then the guest and host effectively share VPID=0. KVM emulates this behavior by using vpid01 when running an L2 with VPID disabled (see prepare_vmcs02_early_rare()), and so KVM must also treat vpid01 as the current VPID while L2 is active. Unconditionally treating vpid02 as the current VPID when L2 is active causes KVM to flush TLB entries for vpid02 instead of vpid01, which results in TLB entries from L1 being incorrectly preserved across nested VM-Enter to L2 (L2=>L1 isn't problematic, because the TLB flush after nested VM-Exit flushes vpid01). The bug manifests as failures in the vmx_apicv_test KVM-Unit-Test, as KVM incorrectly retains TLB entries for the APIC-access page across a nested VM-Enter. Opportunisticaly add comments at various touchpoints to explain the architectural requirements, and also why KVM uses vpid01 instead of vpid02. All credit goes to Chao, who root caused the issue and identified the fix. Link: https://lore.kernel.org/all/ZwzczkIlYGX+QXJz@intel.com Fixes: 2b4a5a5d5688 ("KVM: nVMX: Flush current VPID (L1 vs. L2) for KVM_REQ_TLB_FLUSH_GUEST") Cc: stable@vger.kernel.org Cc: Like Xu Debugged-by: Chao Gao Reviewed-by: Chao Gao Tested-by: Chao Gao Link: https://lore.kernel.org/r/20241031202011.1580522-1-seanjc@google.com Signed-off-by: Sean Christopherson --- arch/x86/kvm/vmx/nested.c | 30 +++++++++++++++++++++++++----- arch/x86/kvm/vmx/vmx.c | 2 +- 2 files changed, 26 insertions(+), 6 deletions(-) diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c index a8e7bc04d9bf..931a7361c30f 100644 --- a/arch/x86/kvm/vmx/nested.c +++ b/arch/x86/kvm/vmx/nested.c @@ -1197,11 +1197,14 @@ static void nested_vmx_transition_tlb_flush(struct kvm_vcpu *vcpu, kvm_hv_nested_transtion_tlb_flush(vcpu, enable_ept); /* - * If vmcs12 doesn't use VPID, L1 expects linear and combined mappings - * for *all* contexts to be flushed on VM-Enter/VM-Exit, i.e. it's a - * full TLB flush from the guest's perspective. This is required even - * if VPID is disabled in the host as KVM may need to synchronize the - * MMU in response to the guest TLB flush. + * If VPID is disabled, then guest TLB accesses use VPID=0, i.e. the + * same VPID as the host, and so architecturally, linear and combined + * mappings for VPID=0 must be flushed at VM-Enter and VM-Exit. KVM + * emulates L2 sharing L1's VPID=0 by using vpid01 while running L2, + * and so KVM must also emulate TLB flush of VPID=0, i.e. vpid01. This + * is required if VPID is disabled in KVM, as a TLB flush (there are no + * VPIDs) still occurs from L1's perspective, and KVM may need to + * synchronize the MMU in response to the guest TLB flush. * * Note, using TLB_FLUSH_GUEST is correct even if nested EPT is in use. * EPT is a special snowflake, as guest-physical mappings aren't @@ -2315,6 +2318,17 @@ static void prepare_vmcs02_early_rare(struct vcpu_vmx *vmx, vmcs_write64(VMCS_LINK_POINTER, INVALID_GPA); + /* + * If VPID is disabled, then guest TLB accesses use VPID=0, i.e. the + * same VPID as the host. Emulate this behavior by using vpid01 for L2 + * if VPID is disabled in vmcs12. Note, if VPID is disabled, VM-Enter + * and VM-Exit are architecturally required to flush VPID=0, but *only* + * VPID=0. I.e. using vpid02 would be ok (so long as KVM emulates the + * required flushes), but doing so would cause KVM to over-flush. E.g. + * if L1 runs L2 X with VPID12=1, then runs L2 Y with VPID12 disabled, + * and then runs L2 X again, then KVM can and should retain TLB entries + * for VPID12=1. + */ if (enable_vpid) { if (nested_cpu_has_vpid(vmcs12) && vmx->nested.vpid02) vmcs_write16(VIRTUAL_PROCESSOR_ID, vmx->nested.vpid02); @@ -5950,6 +5964,12 @@ static int handle_invvpid(struct kvm_vcpu *vcpu) return nested_vmx_fail(vcpu, VMXERR_INVALID_OPERAND_TO_INVEPT_INVVPID); + /* + * Always flush the effective vpid02, i.e. never flush the current VPID + * and never explicitly flush vpid01. INVVPID targets a VPID, not a + * VMCS, and so whether or not the current vmcs12 has VPID enabled is + * irrelevant (and there may not be a loaded vmcs12). + */ vpid02 = nested_get_vpid02(vcpu); switch (type) { case VMX_VPID_EXTENT_INDIVIDUAL_ADDR: diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index 81ed596e4454..9886d67d9512 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -3216,7 +3216,7 @@ void vmx_flush_tlb_all(struct kvm_vcpu *vcpu) static inline int vmx_get_current_vpid(struct kvm_vcpu *vcpu) { - if (is_guest_mode(vcpu)) + if (is_guest_mode(vcpu) && nested_cpu_has_vpid(get_vmcs12(vcpu))) return nested_get_vpid02(vcpu); return to_vmx(vcpu)->vpid; } From e5d253c60e9627a22940e00a05a6115d722f07ed Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Thu, 31 Oct 2024 13:32:14 -0700 Subject: [PATCH 6/6] KVM: SVM: Propagate error from snp_guest_req_init() to userspace If snp_guest_req_init() fails, return the provided error code up the stack to userspace, e.g. so that userspace can log that KVM_SEV_INIT2 failed, as opposed to some random operation later in VM setup failing because SNP wasn't actually enabled for the VM. Note, KVM itself doesn't consult the return value from __sev_guest_init(), i.e. the fallout is purely that userspace may be confused. Fixes: 88caf544c930 ("KVM: SEV: Provide support for SNP_GUEST_REQUEST NAE event") Reported-by: kernel test robot Reported-by: Dan Carpenter Closes: https://lore.kernel.org/r/202410192220.MeTyHPxI-lkp@intel.com Link: https://lore.kernel.org/r/20241031203214.1585751-1-seanjc@google.com Signed-off-by: Sean Christopherson --- arch/x86/kvm/svm/sev.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c index 0b851ef937f2..03c7db3b4cc3 100644 --- a/arch/x86/kvm/svm/sev.c +++ b/arch/x86/kvm/svm/sev.c @@ -450,8 +450,11 @@ static int __sev_guest_init(struct kvm *kvm, struct kvm_sev_cmd *argp, goto e_free; /* This needs to happen after SEV/SNP firmware initialization. */ - if (vm_type == KVM_X86_SNP_VM && snp_guest_req_init(kvm)) - goto e_free; + if (vm_type == KVM_X86_SNP_VM) { + ret = snp_guest_req_init(kvm); + if (ret) + goto e_free; + } INIT_LIST_HEAD(&sev->regions_list); INIT_LIST_HEAD(&sev->mirror_vms);