Commit 689cbe75 authored by James Morse's avatar James Morse Committed by Zeng Heng
Browse files

untested: KVM: arm64: Force guest EL1 to use user-space's partid configuration 

maillist inclusion
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I8T2RT

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/morse/linux.git/log/?h=mpam/snapshot/v6.7-rc2



---------------------------

While we trap the guest's attempts to read/write the MPAM control registers,
these remain in effect. guest-EL0 uses KVM's user-space's configuration,
as the value is left in the register, and guest-EL1 uses either the host
kernel's configuration, or in the case of VHE, the unknown reset value of
MPAM1_EL1.

On nVHE systems, EL2 continues to use partid-0 for world-switch, even
when the host may have configured its kernel threads to use a different
partid. 0 may have been assigned to another task.

We want to force the guest-EL1 to use KVM's user-space's MPAM configuration.

On a nVHE system, copy the EL1 MPAM register to EL2. This ensures
world-switch uses the same partid as the kernel thread does on the host.

When loading the guests EL1 registers, copy the VMM's EL0 partid to
the EL1 register. When restoring the hosts registers, the partid
previously copied to EL2 can be used to restore EL1.

For VHE systems, we can skip restoring the EL1 register for the host,
as it is out-of-context once HCR_EL2.TGE is set.

This is done outside the usual sysreg save/restore as the values can
change behind KVMs back, so should not be stored in the guest context.

Signed-off-by: default avatarJames Morse <james.morse@arm.com>
Signed-off-by: default avatarZeng Heng <zengheng4@huawei.com>
parent 5cd0dad6

arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h

+27 −0
Original line number Diff line number Diff line
@@ -15,6 +15,7 @@ 
#include <asm/kvm_emulate.h>

#include <asm/kvm_hyp.h>

#include <asm/kvm_mmu.h>

#include <asm/mpam.h>



static inline void __sysreg_save_common_state(struct kvm_cpu_context *ctxt)

{
@@ -243,4 +244,30 @@ static inline void __sysreg32_restore_state(struct kvm_vcpu *vcpu) 
		write_sysreg(__vcpu_sys_reg(vcpu, DBGVCR32_EL2), dbgvcr32_el2);

}



/*

 * The _EL0 value was written by the host's context switch, copy this into the

 * guest's EL1.

 */

static inline void __mpam_guest_load(void)

{

	if (IS_ENABLED(CONFIG_ARM64_MPAM) && mpam_cpus_have_feature())

		write_sysreg_el1(read_sysreg_s(SYS_MPAM0_EL1), SYS_MPAM1);

}



/*

 * Copy the _EL2 register back to _EL1, clearing any trap bits EL2 may have set.

 * nVHE world-switch copies the _EL1 register to _EL2. A VHE host writes to the

 * _EL2 register as it is aliased by the hardware when TGE is set.

 */

static inline void __mpam_guest_put(void)

{

	u64 val, mask = MPAM_SYSREG_PMG_D | MPAM_SYSREG_PMG_I |

			MPAM_SYSREG_PARTID_D | MPAM_SYSREG_PARTID_I;

	

	if (IS_ENABLED(CONFIG_ARM64_MPAM) && mpam_cpus_have_feature()) {

		val = FIELD_GET(mask, read_sysreg_s(SYS_MPAM2_EL2));

		write_sysreg_el1(val, SYS_MPAM1);

	}

}



#endif /* __ARM64_KVM_HYP_SYSREG_SR_H__ */

arch/arm64/kvm/hyp/nvhe/switch.c

+11 −0
Original line number Diff line number Diff line
@@ -242,6 +242,13 @@ static void early_exit_filter(struct kvm_vcpu *vcpu, u64 *exit_code) 
	}

}



/* Use the host thread's partid and pmg for world switch */

static void __mpam_copy_el1_to_el2(void)

{

	if (IS_ENABLED(CONFIG_ARM64_MPAM) && mpam_cpus_have_feature())

		write_sysreg_s(read_sysreg_s(SYS_MPAM1_EL1), SYS_MPAM2_EL2);

}



/* Switch to the guest for legacy non-VHE systems */

int __kvm_vcpu_run(struct kvm_vcpu *vcpu)

{
@@ -251,6 +258,8 @@ int __kvm_vcpu_run(struct kvm_vcpu *vcpu) 
	bool pmu_switch_needed;

	u64 exit_code;



	__mpam_copy_el1_to_el2();



	/*

	 * Having IRQs masked via PMR when entering the guest means the GIC

	 * will not signal the CPU of interrupts of lower priority, and the
@@ -310,6 +319,7 @@ int __kvm_vcpu_run(struct kvm_vcpu *vcpu) 
	__timer_enable_traps(vcpu);



	__debug_switch_to_guest(vcpu);

	__mpam_guest_load();



	do {

		/* Jump in the fire! */
@@ -320,6 +330,7 @@ int __kvm_vcpu_run(struct kvm_vcpu *vcpu) 


	__sysreg_save_state_nvhe(guest_ctxt);

	__sysreg32_save_state(vcpu);

	__mpam_guest_put();

	__timer_disable_traps(vcpu);

	__hyp_vgic_save_state(vcpu);

arch/arm64/kvm/hyp/vhe/sysreg-sr.c

+1 −0
Original line number Diff line number Diff line
@@ -90,6 +90,7 @@ void kvm_vcpu_load_sysregs_vhe(struct kvm_vcpu *vcpu) 
	__sysreg32_restore_state(vcpu);

	__sysreg_restore_user_state(guest_ctxt);

	__sysreg_restore_el1_state(guest_ctxt);

	__mpam_guest_load();



	vcpu_set_flag(vcpu, SYSREGS_ON_CPU);