From: Vitaly Kuznetsov <vkuznets@redhat.com>
To: Wanpeng Li <kernellwp@gmail.com>,
linux-kernel@vger.kernel.org, kvm@vger.kernel.org
Cc: Paolo Bonzini <pbonzini@redhat.com>,
Sean Christopherson <sean.j.christopherson@intel.com>,
Wanpeng Li <wanpengli@tencent.com>,
Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>
Subject: Re: [PATCH 2/2] KVM: LAPIC: Set the TDCR settable bits
Date: Tue, 21 Jul 2020 12:51:42 +0200 [thread overview]
Message-ID: <87lfjdp2dd.fsf@vitty.brq.redhat.com> (raw)
In-Reply-To: <1595323468-4380-2-git-send-email-wanpengli@tencent.com>
Wanpeng Li <kernellwp@gmail.com> writes:
> From: Wanpeng Li <wanpengli@tencent.com>
>
> Only bits 0, 1, and 3 are settable, others are reserved for APIC_TDCR.
> Let's record the settable value in the virtual apic page.
>
> Signed-off-by: Wanpeng Li <wanpengli@tencent.com>
> ---
> arch/x86/kvm/lapic.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
> index 4ce2ddd..8f7a14d 100644
> --- a/arch/x86/kvm/lapic.c
> +++ b/arch/x86/kvm/lapic.c
> @@ -2068,7 +2068,7 @@ int kvm_lapic_reg_write(struct kvm_lapic *apic, u32 reg, u32 val)
> case APIC_TDCR: {
> uint32_t old_divisor = apic->divide_count;
>
> - kvm_lapic_set_reg(apic, APIC_TDCR, val);
> + kvm_lapic_set_reg(apic, APIC_TDCR, val & 0xb);
> update_divide_count(apic);
> if (apic->divide_count != old_divisor &&
> apic->lapic_timer.period) {
AFAIU bit 2 should be 0 and other upper bits are reserved. Checking on
bare hardware,
# wrmsr 0x83e 0xb
# rdmsr 0x83e
b
# wrmsr 0x83e 0xc
wrmsr: CPU 0 cannot set MSR 0x0000083e to 0x000000000000000c
# rdmsr 0x83e
b
Shouldn't we fail the write in case (val & ~0xb) ?
--
Vitaly
next prev parent reply other threads:[~2020-07-21 10:51 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-21 9:24 [PATCH 1/2] KVM: LAPIC: Prevent setting the tscdeadline timer if the lapic is hw disabled Wanpeng Li
2020-07-21 9:24 ` [PATCH 2/2] KVM: LAPIC: Set the TDCR settable bits Wanpeng Li
2020-07-21 10:51 ` Vitaly Kuznetsov [this message]
2020-07-27 3:29 ` Wanpeng Li
2020-07-21 10:35 ` [PATCH 1/2] KVM: LAPIC: Prevent setting the tscdeadline timer if the lapic is hw disabled Vitaly Kuznetsov
2020-07-21 15:25 ` Sean Christopherson
2020-07-27 6:18 ` Wanpeng Li
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