lkml.org 
[lkml]   [2019]   [Jan]   [31]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH v10 10/25] arm64: kvm: Unmask PMR before entering guest
Date
Interrupts masked by ICC_PMR_EL1 will not be signaled to the CPU. This
means that hypervisor will not receive masked interrupts while running a
guest.

We need to make sure that all maskable interrupts are masked from the
time we call local_irq_disable() in the main run loop, and remain so
until we call local_irq_enable() after returning from the guest, and we
need to ensure that we see no interrupts at all (including pseudo-NMIs)
in the middle of the VM world-switch, while at the same time we need to
ensure we exit the guest when there are interrupts for the host.

We can accomplish this with pseudo-NMIs enabled by:
(1) local_irq_disable: set the priority mask
(2) enter guest: set PSTATE.I
(3) clear the priority mask
(4) eret to guest
(5) exit guest: set the priotiy mask
clear PSTATE.I (and restore other host PSTATE bits)
(6) local_irq_enable: clear the priority mask.

Signed-off-by: Julien Thierry <julien.thierry@arm.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Reviewed-by: Marc Zyngier <marc.zyngier@arm.com>
Reviewed-by: Christoffer Dall <christoffer.dall@arm.com>
Cc: Christoffer Dall <christoffer.dall@arm.com>
Cc: Marc Zyngier <marc.zyngier@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: kvmarm@lists.cs.columbia.edu
---
arch/arm64/include/asm/kvm_host.h | 16 ++++++++++++++++
arch/arm64/kvm/hyp/switch.c | 16 ++++++++++++++++
2 files changed, 32 insertions(+)

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 7732d0b..292c882 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -24,6 +24,7 @@

#include <linux/types.h>
#include <linux/kvm_types.h>
+#include <asm/arch_gicv3.h>
#include <asm/cpufeature.h>
#include <asm/daifflags.h>
#include <asm/fpsimd.h>
@@ -474,10 +475,25 @@ static inline int kvm_arch_vcpu_run_pid_change(struct kvm_vcpu *vcpu)
static inline void kvm_arm_vhe_guest_enter(void)
{
local_daif_mask();
+
+ /*
+ * Having IRQs masked via PMR when entering the guest means the GIC
+ * will not signal the CPU of interrupts of lower priority, and the
+ * only way to get out will be via guest exceptions.
+ * Naturally, we want to avoid this.
+ */
+ if (system_uses_irq_prio_masking()) {
+ gic_write_pmr(GIC_PRIO_IRQON);
+ dsb(sy);
+ }
}

static inline void kvm_arm_vhe_guest_exit(void)
{
+ /*
+ * local_daif_restore() takes care to properly restore PSTATE.DAIF
+ * and the GIC PMR if the host is using IRQ priorities.
+ */
local_daif_restore(DAIF_PROCCTX_NOIRQ);

/*
diff --git a/arch/arm64/kvm/hyp/switch.c b/arch/arm64/kvm/hyp/switch.c
index b0b1478..6a4c2d6 100644
--- a/arch/arm64/kvm/hyp/switch.c
+++ b/arch/arm64/kvm/hyp/switch.c
@@ -22,6 +22,7 @@

#include <kvm/arm_psci.h>

+#include <asm/arch_gicv3.h>
#include <asm/cpufeature.h>
#include <asm/kvm_asm.h>
#include <asm/kvm_emulate.h>
@@ -521,6 +522,17 @@ int __hyp_text __kvm_vcpu_run_nvhe(struct kvm_vcpu *vcpu)
struct kvm_cpu_context *guest_ctxt;
u64 exit_code;

+ /*
+ * Having IRQs masked via PMR when entering the guest means the GIC
+ * will not signal the CPU of interrupts of lower priority, and the
+ * only way to get out will be via guest exceptions.
+ * Naturally, we want to avoid this.
+ */
+ if (system_uses_irq_prio_masking()) {
+ gic_write_pmr(GIC_PRIO_IRQON);
+ dsb(sy);
+ }
+
vcpu = kern_hyp_va(vcpu);

host_ctxt = kern_hyp_va(vcpu->arch.host_cpu_context);
@@ -573,6 +585,10 @@ int __hyp_text __kvm_vcpu_run_nvhe(struct kvm_vcpu *vcpu)
*/
__debug_switch_to_host(vcpu);

+ /* Returning to host will clear PSR.I, remask PMR if needed */
+ if (system_uses_irq_prio_masking())
+ gic_write_pmr(GIC_PRIO_IRQOFF);
+
return exit_code;
}

--
1.9.1
\
 
 \ /
  Last update: 2019-01-31 16:01    [W:0.132 / U:10.068 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site