Commit c35dd838 authored by Mukesh Ojha's avatar Mukesh Ojha Committed by Marc Zyngier
Browse files

KVM: arm64: Guard PMSCR_EL1 initialization with SPE presence check 



Commit efad60e4 ("KVM: arm64: Initialize PMSCR_EL1 when in VHE")
does not perform sufficient check before initializing PMSCR_EL1 to 0
when running in VHE mode. On some platforms, this causes the system to
hang during boot, as EL3 has not delegated access to the Profiling
Buffer to the Non-secure world, nor does it reinject an UNDEF on sysreg
trap.

To avoid this issue, restrict the PMSCR_EL1 initialization to CPUs that
support Statistical Profiling Extension (FEAT_SPE) and have the
Profiling Buffer accessible in Non-secure EL1. This is determined via a
new helper `cpu_has_spe()` which checks both PMSVer and PMBIDR_EL1.P.

This ensures the initialization only affects CPUs where SPE is
implemented and usable, preventing boot failures on platforms where SPE
is not properly configured.

Fixes: efad60e4 ("KVM: arm64: Initialize PMSCR_EL1 when in VHE")
Signed-off-by: default avatarMukesh Ojha <mukesh.ojha@oss.qualcomm.com>
Signed-off-by: default avatarMarc Zyngier <maz@kernel.org>
parent 9a7f87eb

arch/arm64/kvm/debug.c

+10 −5
Original line number Diff line number Diff line
@@ -15,6 +15,12 @@ 
#include <asm/kvm_arm.h>

#include <asm/kvm_emulate.h>



static int cpu_has_spe(u64 dfr0)

{

	return cpuid_feature_extract_unsigned_field(dfr0, ID_AA64DFR0_EL1_PMSVer_SHIFT) &&

	       !(read_sysreg_s(SYS_PMBIDR_EL1) & PMBIDR_EL1_P);

}



/**

 * kvm_arm_setup_mdcr_el2 - configure vcpu mdcr_el2 value

 *
@@ -77,13 +83,12 @@ void kvm_init_host_debug_data(void) 
	*host_data_ptr(debug_brps) = SYS_FIELD_GET(ID_AA64DFR0_EL1, BRPs, dfr0);

	*host_data_ptr(debug_wrps) = SYS_FIELD_GET(ID_AA64DFR0_EL1, WRPs, dfr0);



	if (cpu_has_spe(dfr0))

		host_data_set_flag(HAS_SPE);



	if (has_vhe())

		return;



	if (cpuid_feature_extract_unsigned_field(dfr0, ID_AA64DFR0_EL1_PMSVer_SHIFT) &&

	    !(read_sysreg_s(SYS_PMBIDR_EL1) & PMBIDR_EL1_P))

		host_data_set_flag(HAS_SPE);



	/* Check if we have BRBE implemented and available at the host */

	if (cpuid_feature_extract_unsigned_field(dfr0, ID_AA64DFR0_EL1_BRBE_SHIFT))

		host_data_set_flag(HAS_BRBE);
@@ -102,7 +107,7 @@ void kvm_init_host_debug_data(void) 
void kvm_debug_init_vhe(void)

{

	/* Clear PMSCR_EL1.E{0,1}SPE which reset to UNKNOWN values. */

	if (SYS_FIELD_GET(ID_AA64DFR0_EL1, PMSVer, read_sysreg(id_aa64dfr0_el1)))

	if (host_data_test_flag(HAS_SPE))

		write_sysreg_el1(0, SYS_PMSCR);

}