Re: [PATCH v7] KVM: s390: Add new reset vcpu API

From: Janosch Frank <frankja@linux.ibm.com>
To: Christian Borntraeger <borntraeger@de.ibm.com>, kvm@vger.kernel.org
Cc: thuth@redhat.com, linux-s390@vger.kernel.org, david@redhat.com,
	cohuck@redhat.com
Subject: Re: [PATCH v7] KVM: s390: Add new reset vcpu API
Date: Mon, 27 Jan 2020 10:52:35 +0100	[thread overview]
Message-ID: <db6d8d0f-8a5e-8c4a-bfbb-027102a21213@linux.ibm.com> (raw)
In-Reply-To: <5a26e1af-ecdc-b815-248e-ee93a7c51ff5@de.ibm.com>

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On 1/27/20 9:05 AM, Christian Borntraeger wrote:
> 
> 
> On 10.01.20 12:45, Janosch Frank wrote:
> [...]
>> +static void kvm_arch_vcpu_ioctl_clear_reset(struct kvm_vcpu *vcpu)
>> +{
>> +	struct kvm_sync_regs *regs = &vcpu->run->s.regs;
>> +
>> +	/* Clear reset is a superset of the initial reset */
>> +	kvm_arch_vcpu_ioctl_normal_reset(vcpu);
>> +
>> +	memset(&regs->gprs, 0, sizeof(regs->gprs));
> 
> 
> 
>> +	/* Will be picked up because of save_fpu_regs() in the initial reset */
>> +	memset(&current->thread.fpu.vxrs, 0, sizeof(current->thread.fpu.vxrs));
> 
> So I checked with a userspace that sets f8(call-saved) to 0x123 during this ioctl.
> f8 is 0 afterwards. The guest f8 is also correct, just because QEMU does clear out
> its copy of the fprs and syncs that back via synv regs.
> 
> So this must be
> 
> 	/* we have not synced the registers from kvm_run to the thread
> 	   structure. We must clear out kvm_run*/
> 	memset(&regs->vrs, 0, sizeof(regs->vrs));

Great, thanks!
Meanwhile I had a look at the missing pieces and the guarded storage resets.

> 
> 
>> +	memset(&regs->acrs, 0, sizeof(regs->acrs));
>> +
>> +	regs->etoken = 0;
>> +	regs->etoken_extension = 0;
>> +
>> +	memset(&regs->gscb, 0, sizeof(regs->gscb));
> [....]
> 

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