linux-kernel - Re: [PATCH RESEND v4 7/9] KVM: VMX: Handle SPP induced vmexit and page fault

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Message-ID: <5f6ba406-17c4-a552-2352-2ff50569aac0@redhat.com>
Date:   Mon, 19 Aug 2019 16:43:32 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Yang Weijiang <weijiang.yang@...el.com>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, sean.j.christopherson@...el.com
Cc:     mst@...hat.com, rkrcmar@...hat.com, jmattson@...gle.com,
        yu.c.zhang@...el.com, alazar@...defender.com
Subject: Re: [PATCH RESEND v4 7/9] KVM: VMX: Handle SPP induced vmexit and
 page fault

On 14/08/19 09:04, Yang Weijiang wrote:
> +			/*
> +			 * Record write protect fault caused by
> +			 * Sub-page Protection, let VMI decide
> +			 * the next step.
> +			 */
> +			if (spte & PT_SPP_MASK) {

Should this be "if (spte & PT_WRITABLE_MASK)" instead?  That is, if the
page is already writable, the fault must be an SPP fault.

Paolo

> +				fault_handled = true;
> +				vcpu->run->exit_reason = KVM_EXIT_SPP;
> +				vcpu->run->spp.addr = gva;
> +				kvm_skip_emulated_instruction(vcpu);
> +				break;
> +			}
> +
>  			new_spte |= PT_WRITABLE_MASK;