From: Vitaly Kuznetsov <vkuznets@redhat.com>
To: Roman Kagan <rvkagan@yandex-team.ru>, Jon Doron <arilou@gmail.com>
Cc: kvm@vger.kernel.org, linux-hyperv@vger.kernel.org
Subject: Re: [PATCH v2 0/1] x86/kvm/hyper-v: Add support to SYNIC exit on EOM
Date: Mon, 04 May 2020 17:55:10 +0200 [thread overview]
Message-ID: <87a72nelup.fsf@vitty.brq.redhat.com> (raw)
In-Reply-To: <20200503191900.GA389956@rvkaganb>
Roman Kagan <rvkagan@yandex-team.ru> writes:
> On Sat, Apr 25, 2020 at 09:16:37AM +0300, Jon Doron wrote:
>
>> If that's indeed the case then probably the only thing needs fixing in my
>> scenario is in QEMU where it should not really care for the SCONTROL if it's
>> enabled or not.
>
> Right. However, even this shouldn't be necessary as SeaBIOS from that
> branch would enable SCONTROL and leave it that way when passing the
> control over to the bootloader, so, unless something explicitly clears
> SCONTROL, it should remain set thereafter. I'd rather try going ahead
> with that scheme first, because making QEMU ignore SCONTROL appears to
> violate the spec.
FWIW, I just checked 'genuine' Hyper-V 2016 with
diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
index fd51bac11b46..c5ea759728d9 100644
--- a/arch/x86/hyperv/hv_init.c
+++ b/arch/x86/hyperv/hv_init.c
@@ -314,10 +314,14 @@ void __init hyperv_init(void)
u64 guest_id, required_msrs;
union hv_x64_msr_hypercall_contents hypercall_msr;
int cpuhp, i;
+ u64 val;
if (x86_hyper_type != X86_HYPER_MS_HYPERV)
return;
+ hv_get_synic_state(val);
+ printk("Hyper-V: SCONTROL state: %llx\n", val);
+
/* Absolutely required MSRs */
required_msrs = HV_X64_MSR_HYPERCALL_AVAILABLE |
HV_X64_MSR_VP_INDEX_AVAILABLE;
and it seems the default state of HV_X64_MSR_SCONTROL is '1', we should
probably do the same. Is there any reason to *not* do this in KVM when
KVM_CAP_HYPERV_SYNIC[,2] is enabled?
--
Vitaly
next prev parent reply other threads:[~2020-05-04 15:55 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-16 8:38 [PATCH v2 0/1] x86/kvm/hyper-v: Add support to SYNIC exit on EOM Jon Doron
2020-04-16 8:38 ` [PATCH v2 1/1] " Jon Doron
2020-04-16 12:00 ` [PATCH v2 0/1] " Roman Kagan
2020-04-16 12:54 ` Jon Doron
2020-04-17 10:42 ` Roman Kagan
2020-04-18 6:41 ` Jon Doron
2020-04-24 12:20 ` Jon Doron
2020-04-24 13:37 ` Roman Kagan
2020-04-25 6:16 ` Jon Doron
2020-05-02 14:47 ` Jon Doron
2020-05-03 19:19 ` Roman Kagan
2020-05-04 15:55 ` Vitaly Kuznetsov [this message]
2020-05-05 8:01 ` Roman Kagan
2020-05-05 10:38 ` Jon Doron
2020-05-05 20:00 ` Roman Kagan
2020-05-06 4:49 ` Jon Doron
2020-05-06 8:46 ` Roman Kagan
2020-05-07 3:00 ` Jon Doron
2020-05-08 14:29 ` Jon Doron
2020-05-08 16:56 ` Roman Kagan
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