linux-kernel - Re: [RFC PATCH v5 060/104] KVM: TDX: Create initial guest memory

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Date:   Thu, 07 Apr 2022 14:30:18 +1200
From:   Kai Huang <kai.huang@...el.com>
To:     isaku.yamahata@...el.com, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     isaku.yamahata@...il.com, Paolo Bonzini <pbonzini@...hat.com>,
        Jim Mattson <jmattson@...gle.com>, erdemaktas@...gle.com,
        Connor Kuehl <ckuehl@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>
Subject: Re: [RFC PATCH v5 060/104] KVM: TDX: Create initial guest memory

On Fri, 2022-03-04 at 11:49 -0800, isaku.yamahata@...el.com wrote:
> +	/*
> +	 * In case of TDP MMU, fault handler can run concurrently.  Note
> +	 * 'source_pa' is a TD scope variable, meaning if there are multiple
> +	 * threads reaching here with all needing to access 'source_pa', it
> +	 * will break.  However fortunately this won't happen, because below
> +	 * TDH_MEM_PAGE_ADD code path is only used when VM is being created
> +	 * before it is running, using KVM_TDX_INIT_MEM_REGION ioctl (which
> +	 * always uses vcpu 0's page table and protected by vcpu->mutex).
> +	 */
> +	WARN_ON(kvm_tdx->source_pa == INVALID_PAGE);

We can just KVM_BUG_ON() and return here.

> +	source_pa = kvm_tdx->source_pa & ~KVM_TDX_MEASURE_MEMORY_REGION;
> +
> +	err = tdh_mem_page_add(kvm_tdx->tdr.pa, gpa, hpa, source_pa, &out);
> +	if (KVM_BUG_ON(err, kvm))
> +		pr_tdx_error(TDH_MEM_PAGE_ADD, err, &out);
> +	else if ((kvm_tdx->source_pa & KVM_TDX_MEASURE_MEMORY_REGION))
> +		tdx_measure_page(kvm_tdx, gpa);
> +
> +	kvm_tdx->source_pa = INVALID_PAGE;