linux-kernel - Re: [PATCH v17 020/116] KVM: TDX: create/destroy VM structure

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Date:   Sun, 19 Nov 2023 14:30:19 +0800
From:   Binbin Wu <binbin.wu@...ux.intel.com>
To:     isaku.yamahata@...el.com
Cc:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        isaku.yamahata@...il.com, Paolo Bonzini <pbonzini@...hat.com>,
        erdemaktas@...gle.com, Sean Christopherson <seanjc@...gle.com>,
        Sagi Shahar <sagis@...gle.com>,
        David Matlack <dmatlack@...gle.com>,
        Kai Huang <kai.huang@...el.com>,
        Zhi Wang <zhi.wang.linux@...il.com>, chen.bo@...el.com,
        hang.yuan@...el.com, tina.zhang@...el.com,
        Sean Christopherson <sean.j.christopherson@...el.com>
Subject: Re: [PATCH v17 020/116] KVM: TDX: create/destroy VM structure



On 11/7/2023 10:55 PM, isaku.yamahata@...el.com wrote:
> From: Isaku Yamahata <isaku.yamahata@...el.com>
>
> As the first step to create TDX guest, create/destroy VM struct.  Assign
> TDX private Host Key ID (HKID) to the TDX guest for memory encryption and
> allocate extra pages for the TDX guest. On destruction, free allocated
> pages, and HKID.
>
> Before tearing down private page tables, TDX requires some resources of the
> guest TD to be destroyed (i.e. HKID must have been reclaimed, etc).  Add
> mmu notifier release callback before tearing down private page tables for
> it.
>
> Add vm_free() of kvm_x86_ops hook at the end of kvm_arch_destroy_vm()
> because some per-VM TDX resources, e.g. TDR, need to be freed after other
> TDX resources, e.g. HKID, were freed.
>
> Co-developed-by: Kai Huang <kai.huang@...el.com>
> Signed-off-by: Kai Huang <kai.huang@...el.com>
> Signed-off-by: Sean Christopherson <sean.j.christopherson@...el.com>
> Signed-off-by: Isaku Yamahata <isaku.yamahata@...el.com>
>
> ---
[...]
> +
> +static int tdx_reclaim_page(hpa_t pa)
> +{
> +	int r;
> +
> +	r = __tdx_reclaim_page(pa);
> +	if (!r)
> +		tdx_clear_page(pa);
> +	return r;
> +}
> +
> +static void tdx_reclaim_td_page(unsigned long td_page_pa)

This function is used to reclaim td control sturcture pages like TDCX, 
TDVPX,
TDVPR. Should this function name be more specific?
For me, it is a bit confusing.

Or maybe do "td page" have specific meaning referring to these control 
structures
pages in TDX?



> +{
> +	WARN_ON_ONCE(!td_page_pa);
> +
> +	/*
> +	 * TDCX are being reclaimed.  TDX module maps TDCX with HKID
> +	 * assigned to the TD.  Here the cache associated to the TD
> +	 * was already flushed by TDH.PHYMEM.CACHE.WB before here, So
> +	 * cache doesn't need to be flushed again.
> +	 */
> +	if (tdx_reclaim_page(td_page_pa))
> +		/*
> +		 * Leak the page on failure:
> +		 * tdx_reclaim_page() returns an error if and only if there's an
> +		 * unexpected, fatal error, e.g. a SEAMCALL with bad params,
> +		 * incorrect concurrency in KVM, a TDX Module bug, etc.
> +		 * Retrying at a later point is highly unlikely to be
> +		 * successful.
> +		 * No log here as tdx_reclaim_page() already did.
> +		 */
> +		return;
> +	free_page((unsigned long)__va(td_page_pa));
> +}
> +
[...]