Commit 53f98558 authored by Andrew Jones's avatar Andrew Jones Committed by Marc Zyngier
Browse files

KVM: arm64: pvtime: Fix stolen time accounting across migration 



When updating the stolen time we should always read the current
stolen time from the user provided memory, not from a kernel
cache. If we use a cache then we'll end up resetting stolen time
to zero on the first update after migration.

Signed-off-by: default avatarAndrew Jones <drjones@redhat.com>
Signed-off-by: default avatarMarc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20200804170604.42662-5-drjones@redhat.com
parent 4d2d4ce0

arch/arm64/include/asm/kvm_host.h

+0 −1
Original line number Diff line number Diff line
@@ -368,7 +368,6 @@ struct kvm_vcpu_arch { 


	/* Guest PV state */

	struct {

		u64 steal;

		u64 last_steal;

		gpa_t base;

	} steal;

arch/arm64/kvm/pvtime.c

+9 −14
Original line number Diff line number Diff line
@@ -13,26 +13,22 @@ 
void kvm_update_stolen_time(struct kvm_vcpu *vcpu)

{

	struct kvm *kvm = vcpu->kvm;

	u64 base = vcpu->arch.steal.base;

	u64 last_steal = vcpu->arch.steal.last_steal;

	u64 steal;

	__le64 steal_le;

	u64 offset;

	u64 offset = offsetof(struct pvclock_vcpu_stolen_time, stolen_time);

	u64 steal = 0;

	int idx;

	u64 base = vcpu->arch.steal.base;



	if (base == GPA_INVALID)

		return;



	/* Let's do the local bookkeeping */

	steal = vcpu->arch.steal.steal;

	idx = srcu_read_lock(&kvm->srcu);

	if (!kvm_get_guest(kvm, base + offset, steal)) {

		steal = le64_to_cpu(steal);

		vcpu->arch.steal.last_steal = READ_ONCE(current->sched_info.run_delay);

		steal += vcpu->arch.steal.last_steal - last_steal;

	vcpu->arch.steal.steal = steal;



	steal_le = cpu_to_le64(steal);

	idx = srcu_read_lock(&kvm->srcu);

	offset = offsetof(struct pvclock_vcpu_stolen_time, stolen_time);

	kvm_put_guest(kvm, base + offset, steal_le);

		kvm_put_guest(kvm, base + offset, cpu_to_le64(steal));

	}

	srcu_read_unlock(&kvm->srcu, idx);

}
@@ -66,7 +62,6 @@ gpa_t kvm_init_stolen_time(struct kvm_vcpu *vcpu) 
	 * Start counting stolen time from the time the guest requests

	 * the feature enabled.

	 */

	vcpu->arch.steal.steal = 0;

	vcpu->arch.steal.last_steal = current->sched_info.run_delay;



	idx = srcu_read_lock(&kvm->srcu);

include/linux/kvm_host.h

+20 −0
Original line number Diff line number Diff line
@@ -749,6 +749,26 @@ int kvm_write_guest_offset_cached(struct kvm *kvm, struct gfn_to_hva_cache *ghc, 
int kvm_gfn_to_hva_cache_init(struct kvm *kvm, struct gfn_to_hva_cache *ghc,

			      gpa_t gpa, unsigned long len);



#define __kvm_get_guest(kvm, gfn, offset, v)				\

({									\

	unsigned long __addr = gfn_to_hva(kvm, gfn);			\

	typeof(v) __user *__uaddr = (typeof(__uaddr))(__addr + offset);	\

	int __ret = -EFAULT;						\

									\

	if (!kvm_is_error_hva(__addr))					\

		__ret = get_user(v, __uaddr);				\

	__ret;								\

})



#define kvm_get_guest(kvm, gpa, v)					\

({									\

	gpa_t __gpa = gpa;						\

	struct kvm *__kvm = kvm;					\

									\

	__kvm_get_guest(__kvm, __gpa >> PAGE_SHIFT,			\

			offset_in_page(__gpa), v);			\

})



#define __kvm_put_guest(kvm, gfn, offset, v)				\

({									\

	unsigned long __addr = gfn_to_hva(kvm, gfn);			\

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