linux-kernel - Re: [PATCH v8 7/7] arm64: kvm: handle SError Interrupt by categorization

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Date:   Fri, 15 Dec 2017 11:30:57 +0800
From:   gengdongjiu <gengdongjiu@...wei.com>
To:     James Morse <james.morse@....com>
CC:     <christoffer.dall@...aro.org>, <marc.zyngier@....com>,
        <linux@...linux.org.uk>, <bp@...en8.de>, <rjw@...ysocki.net>,
        <pbonzini@...hat.com>, <rkrcmar@...hat.com>, <corbet@....net>,
        <catalin.marinas@....com>, <kvm@...r.kernel.org>,
        <linux-doc@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <kvmarm@...ts.cs.columbia.edu>, <linux-acpi@...r.kernel.org>,
        <devel@...ica.org>, <huangshaoyu@...wei.com>,
        <wuquanming@...wei.com>, <linuxarm@...wei.com>
Subject: Re: [PATCH v8 7/7] arm64: kvm: handle SError Interrupt by
 categorization

Hi James,

On 2017/12/7 14:37, gengdongjiu wrote:
>> We need to tackle (1) and (3) separately. For (3) we need some API that lets
>> Qemu _trigger_ an SError in the guest, with a specified ESR. But, we don't have
>> a way of migrating pending SError yet... which is where I got stuck last time I
>> was looking at this.
> I understand you most idea.
> 
> But In the Qemu one signal type can only correspond to one behavior, can not correspond to two behaviors,
> otherwise Qemu will do not know how to do.
> 
> For the Qemu, if it receives the SIGBUS_MCEERR_AR signal, it will populate the CPER
> records and inject a SEA to guest through KVM IOCTL "KVM_SET_ONE_REG"; if receives the SIGBUS_MCEERR_AO
> signal, it will record the CPER and trigger a IRQ to notify guest, as shown below:
> 
> SIGBUS_MCEERR_AR trigger Synchronous External Abort.
> SIGBUS_MCEERR_AO trigger GPIO IRQ.
> 
> For the SIGBUS_MCEERR_AO and SIGBUS_MCEERR_AR, we have already specify trigger method, which all
> 
> not involve _trigger_ an SError.
> 
> so there is no chance for Qemu to trigger the SError when gets the SIGBUS_MCEERR_A{O,R}.

As I explained above:

If Qemu received SIGBUS_MCEERR_AR, it will record CPER and trigger Synchronous External Abort;
If Qemu received SIGBUS_MCEERR_AO, it will record CPER and trigger GPIO IRQ;
So Qemu does not know when to _trigger_ an SError.

so here I "return a error" to Qemu if ghes_notify_sei() return failure in [1], if you opposed KVM "return error",
do you have a better idea about it? thanks

About the way of migrating pending SError, I think it is a separate case, because Qemu still does not know
how and when to trigger the SError.

[1]:
static int kvm_handle_guest_sei(struct kvm_vcpu *vcpu, struct kvm_run *run)
{
        .......................
+       case ESR_ELx_AET_UER:   /* The error has not been propagated */
+               /*
+                * Userspace only handle the guest SError Interrupt(SEI) if the
+                * error has not been propagated
+                */
+               run->exit_reason = KVM_EXIT_EXCEPTION;
+               run->ex.exception = ESR_ELx_EC_SERROR;
+               run->ex.error_code = KVM_SEI_SEV_RECOVERABLE;
+               return 0;
        .......................
}

>