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SubjectRe: [PATCH v2 12/15] kvm: i8254: Check LAPIC EOI pending when injecting irq on SVM AVIC
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On 15.08.19 18:25, Suthikulpanit, Suravee wrote:
> ACK notifiers don't work with AMD SVM w/ AVIC when the PIT interrupt
> is delivered as edge-triggered fixed interrupt since AMD processors
> cannot exit on EOI for these interrupts.
>
> Add code to check LAPIC pending EOI before injecting any pending PIT
> interrupt on AMD SVM when AVIC is activated.
>
> Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
> ---
> arch/x86/kvm/i8254.c | 31 +++++++++++++++++++++++++------
> 1 file changed, 25 insertions(+), 6 deletions(-)
>
> diff --git a/arch/x86/kvm/i8254.c b/arch/x86/kvm/i8254.c
> index 4a6dc54..31c4a9b 100644
> --- a/arch/x86/kvm/i8254.c
> +++ b/arch/x86/kvm/i8254.c
> @@ -34,10 +34,12 @@
>
> #include <linux/kvm_host.h>
> #include <linux/slab.h>
> +#include <asm/virtext.h>
>
> #include "ioapic.h"
> #include "irq.h"
> #include "i8254.h"
> +#include "lapic.h"
> #include "x86.h"
>
> #ifndef CONFIG_X86_64
> @@ -236,6 +238,12 @@ static void destroy_pit_timer(struct kvm_pit *pit)
> kthread_flush_work(&pit->expired);
> }
>
> +static inline void kvm_pit_reset_reinject(struct kvm_pit *pit)
> +{
> + atomic_set(&pit->pit_state.pending, 0);
> + atomic_set(&pit->pit_state.irq_ack, 1);
> +}
> +
> static void pit_do_work(struct kthread_work *work)
> {
> struct kvm_pit *pit = container_of(work, struct kvm_pit, expired);
> @@ -244,6 +252,23 @@ static void pit_do_work(struct kthread_work *work)
> int i;
> struct kvm_kpit_state *ps = &pit->pit_state;
>
> + /*
> + * Since, AMD SVM AVIC accelerates write access to APIC EOI
> + * register for edge-trigger interrupts. PIT will not be able
> + * to receive the IRQ ACK notifier and will always be zero.
> + * Therefore, we check if any LAPIC EOI pending for vector 0
> + * and reset irq_ack if no pending.
> + */
> + if (cpu_has_svm(NULL) && kvm->arch.apicv_state == APICV_ACTIVATED) {
> + int eoi = 0;
> +
> + kvm_for_each_vcpu(i, vcpu, kvm)
> + if (kvm_apic_pending_eoi(vcpu, 0))
> + eoi++;
> + if (!eoi)
> + kvm_pit_reset_reinject(pit);

In which case would eoi be != 0 when APIC-V is active?


Alex

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