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KVM: arm64: nv: Emulate PSTATE.M for a guest hypervisor

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We can no longer blindly copy the VCPU's PSTATE into SPSR_EL2 and return
to the guest and vice versa when taking an exception to the hypervisor,
because we emulate virtual EL2 in EL1 and therefore have to translate
the mode field from EL2 to EL1 and vice versa.

This requires keeping track of the state we enter the guest, for which
we transiently use a dedicated flag.

Reviewed-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Reviewed-by: Alexandru Elisei <alexandru.elisei@arm.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20230209175820.1939006-15-maz@kernel.org
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
This commit is contained in:
Marc Zyngier 2023-02-09 17:58:16 +00:00 committed by Oliver Upton
parent 9da117eec9
commit d9552fe133
3 changed files with 44 additions and 1 deletions
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2
arch/arm64/include/asm/kvm_host.h
View file

@ -645,6 +645,8 @@ struct kvm_vcpu_arch {
#define DEBUG_STATE_SAVE_SPE __vcpu_single_flag(iflags, BIT(5))
/* Save TRBE context if active */
#define DEBUG_STATE_SAVE_TRBE __vcpu_single_flag(iflags, BIT(6))
/* vcpu running in HYP context */
#define VCPU_HYP_CONTEXT __vcpu_single_flag(iflags, BIT(7))
/* SVE enabled for host EL0 */
#define HOST_SVE_ENABLED __vcpu_single_flag(sflags, BIT(0))

19
arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h
View file

@ -156,9 +156,26 @@ static inline void __sysreg_restore_el1_state(struct kvm_cpu_context *ctxt)
write_sysreg_el1(ctxt_sys_reg(ctxt, SPSR_EL1), SYS_SPSR);
}
/* Read the VCPU state's PSTATE, but translate (v)EL2 to EL1. */
static inline u64 to_hw_pstate(const struct kvm_cpu_context *ctxt)
{
u64 mode = ctxt->regs.pstate & (PSR_MODE_MASK | PSR_MODE32_BIT);
switch (mode) {
case PSR_MODE_EL2t:
mode = PSR_MODE_EL1t;
break;
case PSR_MODE_EL2h:
mode = PSR_MODE_EL1h;
break;
}
return (ctxt->regs.pstate & ~(PSR_MODE_MASK | PSR_MODE32_BIT)) | mode;
}
static inline void __sysreg_restore_el2_return_state(struct kvm_cpu_context *ctxt)
{
u64 pstate = ctxt->regs.pstate;
u64 pstate = to_hw_pstate(ctxt);
u64 mode = pstate & PSR_AA32_MODE_MASK;
/*

24
arch/arm64/kvm/hyp/vhe/switch.c
View file

@ -120,6 +120,25 @@ static const exit_handler_fn *kvm_get_exit_handler_array(struct kvm_vcpu *vcpu)
static void early_exit_filter(struct kvm_vcpu *vcpu, u64 *exit_code)
{
/*
* If we were in HYP context on entry, adjust the PSTATE view
* so that the usual helpers work correctly.
*/
if (unlikely(vcpu_get_flag(vcpu, VCPU_HYP_CONTEXT))) {
u64 mode = *vcpu_cpsr(vcpu) & (PSR_MODE_MASK | PSR_MODE32_BIT);
switch (mode) {
case PSR_MODE_EL1t:
mode = PSR_MODE_EL2t;
break;
case PSR_MODE_EL1h:
mode = PSR_MODE_EL2h;
break;
}
*vcpu_cpsr(vcpu) &= ~(PSR_MODE_MASK | PSR_MODE32_BIT);
*vcpu_cpsr(vcpu) |= mode;
}
}
/* Switch to the guest for VHE systems running in EL2 */
@ -154,6 +173,11 @@ static int __kvm_vcpu_run_vhe(struct kvm_vcpu *vcpu)
sysreg_restore_guest_state_vhe(guest_ctxt);
__debug_switch_to_guest(vcpu);
if (is_hyp_ctxt(vcpu))
vcpu_set_flag(vcpu, VCPU_HYP_CONTEXT);
else
vcpu_clear_flag(vcpu, VCPU_HYP_CONTEXT);
do {
/* Jump in the fire! */
exit_code = __guest_enter(vcpu);