On Tue, Sep 17, 2019 at 11:57:53AM -0700, Marc Orr wrote:
> Excerise nested VMX's atomic MSR switch code (e.g., VM-entry MSR-load
> list) at the maximum number of MSRs supported, as described in the SDM,
> in the appendix chapter titled "MISCELLANEOUS DATA".
>
> Suggested-by: Jim Mattson <jmattson@xxxxxxxxxx>
> Signed-off-by: Marc Orr <marcorr@xxxxxxxxxx>
> ---
> lib/alloc_page.c | 5 ++
> lib/alloc_page.h | 1 +
> x86/unittests.cfg | 2 +-
> x86/vmx_tests.c | 131 ++++++++++++++++++++++++++++++++++++++++++++++
> 4 files changed, 138 insertions(+), 1 deletion(-)
>
> diff --git a/lib/alloc_page.c b/lib/alloc_page.c
> index 97d13395ff08..ed236389537e 100644
> --- a/lib/alloc_page.c
> +++ b/lib/alloc_page.c
> @@ -53,6 +53,11 @@ void free_pages(void *mem, unsigned long size)
> spin_unlock(&lock);
> }
>
> +void free_pages_by_order(void *mem, unsigned long order)
> +{
> + free_pages(mem, 1ul << (order + PAGE_SHIFT));
> +}
> +
> void *alloc_page()
> {
> void *p;
> diff --git a/lib/alloc_page.h b/lib/alloc_page.h
> index 5cdfec57a0a8..739a91def979 100644
> --- a/lib/alloc_page.h
> +++ b/lib/alloc_page.h
> @@ -14,5 +14,6 @@ void *alloc_page(void);
> void *alloc_pages(unsigned long order);
> void free_page(void *page);
> void free_pages(void *mem, unsigned long size);
> +void free_pages_by_order(void *mem, unsigned long order);
>
> #endif
> diff --git a/x86/unittests.cfg b/x86/unittests.cfg
> index 694ee3d42f3a..05122cf91ea1 100644
> --- a/x86/unittests.cfg
> +++ b/x86/unittests.cfg
> @@ -227,7 +227,7 @@ extra_params = -cpu qemu64,+umip
>
> [vmx]
> file = vmx.flat
> -extra_params = -cpu host,+vmx -append "-exit_monitor_from_l2_test -ept_access* -vmx_smp* -vmx_vmcs_shadow_test"
> +extra_params = -cpu host,+vmx -append "-exit_monitor_from_l2_test -ept_access* -vmx_smp* -vmx_vmcs_shadow_test -atomic_switch_overflow_msrs_test"
> arch = x86_64
> groups = vmx
>
> diff --git a/x86/vmx_tests.c b/x86/vmx_tests.c
> index f035f24a771a..fb665f38b1e5 100644
> --- a/x86/vmx_tests.c
> +++ b/x86/vmx_tests.c
> @@ -8570,6 +8570,134 @@ static int invalid_msr_entry_failure(struct vmentry_failure *failure)
> return VMX_TEST_VMEXIT;
> }
>
> +/*
> + * The max number of MSRs in an atomic switch MSR list is:
> + * (111B + 1) * 512 = 4096
> + *
> + * Each list entry consumes:
> + * 4-byte MSR index + 4 bytes reserved + 8-byte data = 16 bytes
> + *
> + * Allocate 128 kB to cover max_msr_list_size (i.e., 64 kB) and then some.
> + */
> +static const u32 msr_list_page_order = 5;
> +
> +static void atomic_switch_msr_limit_test_guest(void)
> +{
> + vmcall();
> +}
> +
> +static void populate_msr_list(struct vmx_msr_entry *msr_list,
> + size_t byte_capacity, int count)
> +{
> + int i;
> +
> + for (i = 0; i < count; i++) {
> + msr_list[i].index = MSR_IA32_TSC;
> + msr_list[i].reserved = 0;
> + msr_list[i].value = 0x1234567890abcdef;
> + }
> +
> + memset(msr_list + count, 0xff,
> + byte_capacity - count * sizeof(*msr_list));
> +}
> +
> +static int max_msr_list_size(void)
> +{
> + u32 vmx_misc = rdmsr(MSR_IA32_VMX_MISC);
> + u32 factor = ((vmx_misc & GENMASK(27, 25)) >> 25) + 1;
> +
> + return factor * 512;
> +}
> +
> +static void atomic_switch_msrs_test(int count)
> +{
> + struct vmx_msr_entry *vm_enter_load;
> + struct vmx_msr_entry *vm_exit_load;
> + struct vmx_msr_entry *vm_exit_store;
Spaces need to be replaced with tabs.
> + int max_allowed = max_msr_list_size();
> + int byte_capacity = 1ul << (msr_list_page_order + PAGE_SHIFT);
> + /* Exceeding the max MSR list size at exit trigers KVM to abort. */
s/trigers/triggers
The whole sentence kinda is kinda funky. Maybe
/* KVM signals VM-Abort if an exit MSR list exceeds the max size. */
> + int exit_count = count > max_allowed ? max_allowed : count;
If only we had MIN()... ;-)
> + int cleanup_count = count > max_allowed ? 2 : 1;
> + int i;
> +
> + /*
> + * Check for the IA32_TSC MSR,
> + * available with the "TSC flag" and used to populate the MSR lists.
> + */
> + if (!(cpuid(1).d & (1 << 4))) {
> + report_skip(__func__);
> + return;
> + }
> +
> + /* Set L2 guest. */
> + test_set_guest(atomic_switch_msr_limit_test_guest);
> +
> + /* Setup atomic MSR switch lists. */
> + vm_enter_load = alloc_pages(msr_list_page_order);
> + vm_exit_load = alloc_pages(msr_list_page_order);
> + vm_exit_store = alloc_pages(msr_list_page_order);
> +
> + vmcs_write(ENTER_MSR_LD_ADDR, (u64)vm_enter_load);
> + vmcs_write(EXIT_MSR_LD_ADDR, (u64)vm_exit_load);
> + vmcs_write(EXIT_MSR_ST_ADDR, (u64)vm_exit_store);
> +
> + /*
> + * VM-Enter should succeed up to the max number of MSRs per list, and
> + * should not consume junk beyond the last entry.
> + */
> + populate_msr_list(vm_enter_load, byte_capacity, count);
> + populate_msr_list(vm_exit_load, byte_capacity, exit_count);
> + populate_msr_list(vm_exit_store, byte_capacity, exit_count);
> +
> + vmcs_write(ENT_MSR_LD_CNT, count);
> + vmcs_write(EXI_MSR_LD_CNT, exit_count);
> + vmcs_write(EXI_MSR_ST_CNT, exit_count);
> +
> + if (count <= max_allowed) {
> + enter_guest();
> + assert_exit_reason(VMX_VMCALL);
> + skip_exit_vmcall();
> + } else {
> + u32 exit_reason;
> + u32 exit_reason_want;
> + u32 exit_qual;
> +
> + enter_guest_with_invalid_guest_state();
> +
> + exit_reason = vmcs_read(EXI_REASON);
> + exit_reason_want = VMX_FAIL_MSR | VMX_ENTRY_FAILURE;
> + report("exit_reason, %u, is %u.",
> + exit_reason == exit_reason_want, exit_reason,
> + exit_reason_want);
> +
> + exit_qual = vmcs_read(EXI_QUALIFICATION);
> + report("exit_qual, %u, is %u.", exit_qual == max_allowed + 1,
> + exit_qual, max_allowed + 1);
> + }
> +
> + /* Cleanup. */
> + vmcs_write(ENT_MSR_LD_CNT, 0);
> + vmcs_write(EXI_MSR_LD_CNT, 0);
> + vmcs_write(EXI_MSR_ST_CNT, 0);
> + for (i = 0; i < cleanup_count; i++) {
> + enter_guest();
> + skip_exit_vmcall();
> + }
I'm missing something, why do we need to reenter the guest after setting
the count to 0?
> + free_pages_by_order(vm_enter_load, msr_list_page_order);
> + free_pages_by_order(vm_exit_load, msr_list_page_order);
> + free_pages_by_order(vm_exit_store, msr_list_page_order);
> +}
> +
> +static void atomic_switch_max_msrs_test(void)
> +{
> + atomic_switch_msrs_test(max_msr_list_size());
> +}
> +
> +static void atomic_switch_overflow_msrs_test(void)
> +{
> + atomic_switch_msrs_test(max_msr_list_size() + 1);
> +}
>
> #define TEST(name) { #name, .v2 = name }
>
> @@ -8660,5 +8788,8 @@ struct vmx_test vmx_tests[] = {
> TEST(ept_access_test_paddr_read_execute_ad_enabled),
> TEST(ept_access_test_paddr_not_present_page_fault),
> TEST(ept_access_test_force_2m_page),
> + /* Atomic MSR switch tests. */
> + TEST(atomic_switch_max_msrs_test),
> + TEST(atomic_switch_overflow_msrs_test),
> { NULL, NULL, NULL, NULL, NULL, {0} },
> };
> --
> 2.23.0.237.gc6a4ce50a0-goog
>
