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Date: Fri, 30 Jul 2021 16:50:06 +0200
From: Vitaly Kuznetsov <vkuznets@...hat.com>
To: Siddharth Chandrasekaran <sidcha@...zon.de>
Cc: kvm@...r.kernel.org, Paolo Bonzini <pbonzini@...hat.com>,
Sean Christopherson <seanjc@...gle.com>,
Wanpeng Li <wanpengli@...cent.com>,
Jim Mattson <jmattson@...gle.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 4/4] KVM: selftests: Test access to XMM fast hypercalls
Siddharth Chandrasekaran <sidcha@...zon.de> writes:
> On Fri, Jul 30, 2021 at 02:26:25PM +0200, Vitaly Kuznetsov wrote:
>> HYPERV_CPUID_FEATURES.EDX and an 'XMM fast' hypercall is issued.
>>
>> Signed-off-by: Vitaly Kuznetsov <vkuznets@...hat.com>
>> ---
>> .../selftests/kvm/include/x86_64/hyperv.h | 5 ++-
>> .../selftests/kvm/x86_64/hyperv_features.c | 41 +++++++++++++++++--
>> 2 files changed, 42 insertions(+), 4 deletions(-)
>>
>> diff --git a/tools/testing/selftests/kvm/include/x86_64/hyperv.h b/tools/testing/selftests/kvm/include/x86_64/hyperv.h
>> index 412eaee7884a..b66910702c0a 100644
>> --- a/tools/testing/selftests/kvm/include/x86_64/hyperv.h
>> +++ b/tools/testing/selftests/kvm/include/x86_64/hyperv.h
>> @@ -117,7 +117,7 @@
>> #define HV_X64_GUEST_DEBUGGING_AVAILABLE BIT(1)
>> #define HV_X64_PERF_MONITOR_AVAILABLE BIT(2)
>> #define HV_X64_CPU_DYNAMIC_PARTITIONING_AVAILABLE BIT(3)
>> -#define HV_X64_HYPERCALL_PARAMS_XMM_AVAILABLE BIT(4)
>> +#define HV_X64_HYPERCALL_XMM_INPUT_AVAILABLE BIT(4)
>> #define HV_X64_GUEST_IDLE_STATE_AVAILABLE BIT(5)
>> #define HV_FEATURE_FREQUENCY_MSRS_AVAILABLE BIT(8)
>> #define HV_FEATURE_GUEST_CRASH_MSR_AVAILABLE BIT(10)
>> @@ -182,4 +182,7 @@
>> #define HV_STATUS_INVALID_CONNECTION_ID 18
>> #define HV_STATUS_INSUFFICIENT_BUFFERS 19
>>
>> +/* hypercall options */
>> +#define HV_HYPERCALL_FAST_BIT BIT(16)
>> +
>> #endif /* !SELFTEST_KVM_HYPERV_H */
>> diff --git a/tools/testing/selftests/kvm/x86_64/hyperv_features.c b/tools/testing/selftests/kvm/x86_64/hyperv_features.c
>> index af27c7e829c1..91d88aaa9899 100644
>> --- a/tools/testing/selftests/kvm/x86_64/hyperv_features.c
>> +++ b/tools/testing/selftests/kvm/x86_64/hyperv_features.c
>> @@ -47,6 +47,7 @@ static void do_wrmsr(u32 idx, u64 val)
>> }
>>
>> static int nr_gp;
>> +static int nr_ud;
>>
>> static inline u64 hypercall(u64 control, vm_vaddr_t input_address,
>> vm_vaddr_t output_address)
>> @@ -80,6 +81,12 @@ static void guest_gp_handler(struct ex_regs *regs)
>> regs->rip = (uint64_t)&wrmsr_end;
>> }
>>
>> +static void guest_ud_handler(struct ex_regs *regs)
>> +{
>> + nr_ud++;
>> + regs->rip += 3;
>> +}
>> +
>> struct msr_data {
>> uint32_t idx;
>> bool available;
>> @@ -90,6 +97,7 @@ struct msr_data {
>> struct hcall_data {
>> uint64_t control;
>> uint64_t expect;
>> + bool ud_expected;
>> };
>>
>> static void guest_msr(struct msr_data *msr)
>> @@ -117,13 +125,26 @@ static void guest_msr(struct msr_data *msr)
>> static void guest_hcall(vm_vaddr_t pgs_gpa, struct hcall_data *hcall)
>> {
>> int i = 0;
>> + u64 res, input, output;
>>
>> wrmsr(HV_X64_MSR_GUEST_OS_ID, LINUX_OS_ID);
>> wrmsr(HV_X64_MSR_HYPERCALL, pgs_gpa);
>>
>> while (hcall->control) {
>> - GUEST_ASSERT(hypercall(hcall->control, pgs_gpa,
>> - pgs_gpa + 4096) == hcall->expect);
>> + nr_ud = 0;
>> + if (!(hcall->control & HV_HYPERCALL_FAST_BIT)) {
>> + input = pgs_gpa;
>> + output = pgs_gpa + 4096;
>> + } else {
>> + input = output = 0;
>> + }
>> +
>> + res = hypercall(hcall->control, input, output);
>> + if (hcall->ud_expected)
>> + GUEST_ASSERT(nr_ud == 1);
>
> Should we also do WRITE_ONCE(nr_ur, 0) here?
It could probably make sense to replace 'nr_ud = 0' above with this so
compiler doesn't screw us up one day..
> or perhaps pass the the
> expected value of nr_ud + 1 in hcall->ud_expected from caller and do,
>
> if (hcall->ud_expected)
> GUEST_ASSERT(nr_ud == hcall->ud_expected);
>
> This way there can be other test that can also expect a UD.
My idea was that we don't really need to count #UDs for now, just
checking the fact that it happened is OK so I reset nr_ud before doing
the hypercall and check it after. It is possible to add more tests with
'ud_expected' this way.
>
>> + else
>> + GUEST_ASSERT(res == hcall->expect);
>> +
>> GUEST_SYNC(i++);
>> }
>>
>> @@ -552,8 +573,18 @@ static void guest_test_hcalls_access(struct kvm_vm *vm, struct hcall_data *hcall
>> recomm.ebx = 0xfff;
>> hcall->expect = HV_STATUS_SUCCESS;
>> break;
>> -
>> case 17:
>> + /* XMM fast hypercall */
>> + hcall->control = HVCALL_FLUSH_VIRTUAL_ADDRESS_SPACE | HV_HYPERCALL_FAST_BIT;
>> + hcall->ud_expected = true;
>> + break;
>> + case 18:
>> + feat.edx |= HV_X64_HYPERCALL_XMM_INPUT_AVAILABLE;
>> + hcall->ud_expected = false;
>> + hcall->expect = HV_STATUS_SUCCESS;
>> + break;
>> +
>> + case 19:
>> /* END */
>> hcall->control = 0;
>> break;
>> @@ -625,6 +656,10 @@ int main(void)
>> /* Test hypercalls */
>> vm = vm_create_default(VCPU_ID, 0, guest_hcall);
>>
>> + vm_init_descriptor_tables(vm);
>> + vcpu_init_descriptor_tables(vm, VCPU_ID);
>> + vm_install_exception_handler(vm, UD_VECTOR, guest_ud_handler);
>> +
>> /* Hypercall input/output */
>> hcall_page = vm_vaddr_alloc_pages(vm, 2);
>> memset(addr_gva2hva(vm, hcall_page), 0x0, 2 * getpagesize());
>> --
>> 2.31.1
>>
>
>
>
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>
>
>
--
Vitaly
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