Commit 08a82824 authored by Sean Christopherson's avatar Sean Christopherson
Browse files

KVM: selftests: Verify post-RESET value of PERF_GLOBAL_CTRL in PMCs test 



Add a guest assert in the PMU counters test to verify that KVM stuffs
the vCPU's post-RESET value to globally enable all general purpose
counters.  Per Intel's SDM,

  IA32_PERF_GLOBAL_CTRL:  Sets bits n-1:0 and clears the upper bits.

and

  Where "n" is the number of general-purpose counters available in
  the processor.

For the edge case where there are zero GP counters, follow the spirit
of the architecture, not the SDM's literal wording, which doesn't account
for this possibility and would require the CPU to set _all_ bits in
PERF_GLOBAL_CTRL.

Reviewed-by: default avatarDapeng Mi <dapeng1.mi@linux.intel.com>
Tested-by: default avatarDapeng Mi <dapeng1.mi@linux.intel.com>
Link: https://lore.kernel.org/r/20240309013641.1413400-3-seanjc@google.com


Signed-off-by: default avatarSean Christopherson <seanjc@google.com>
parent de120e1d

tools/testing/selftests/kvm/x86_64/pmu_counters_test.c

+19 −1
Original line number Diff line number Diff line
@@ -416,12 +416,30 @@ static void guest_rd_wr_counters(uint32_t base_msr, uint8_t nr_possible_counters 


static void guest_test_gp_counters(void)

{

	uint8_t pmu_version = guest_get_pmu_version();

	uint8_t nr_gp_counters = 0;

	uint32_t base_msr;



	if (guest_get_pmu_version())

	if (pmu_version)

		nr_gp_counters = this_cpu_property(X86_PROPERTY_PMU_NR_GP_COUNTERS);



	/*

	 * For v2+ PMUs, PERF_GLOBAL_CTRL's architectural post-RESET value is

	 * "Sets bits n-1:0 and clears the upper bits", where 'n' is the number

	 * of GP counters.  If there are no GP counters, require KVM to leave

	 * PERF_GLOBAL_CTRL '0'.  This edge case isn't covered by the SDM, but

	 * follow the spirit of the architecture and only globally enable GP

	 * counters, of which there are none.

	 */

	if (pmu_version > 1) {

		uint64_t global_ctrl = rdmsr(MSR_CORE_PERF_GLOBAL_CTRL);



		if (nr_gp_counters)

			GUEST_ASSERT_EQ(global_ctrl, GENMASK_ULL(nr_gp_counters - 1, 0));

		else

			GUEST_ASSERT_EQ(global_ctrl, 0);

	}



	if (this_cpu_has(X86_FEATURE_PDCM) &&

	    rdmsr(MSR_IA32_PERF_CAPABILITIES) & PMU_CAP_FW_WRITES)

		base_msr = MSR_IA32_PMC0;