linux-kernel - Re: [PATCH v1 6/7] x86/kvm: Use bounce buffers for TD guest

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Date:   Fri, 11 Jun 2021 09:52:49 -0500
From:   Tom Lendacky <thomas.lendacky@....com>
To:     Kuppuswamy Sathyanarayanan 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Andy Lutomirski <luto@...nel.org>
Cc:     Peter H Anvin <hpa@...or.com>, Dave Hansen <dave.hansen@...el.com>,
        Tony Luck <tony.luck@...el.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Kirill Shutemov <kirill.shutemov@...ux.intel.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Kuppuswamy Sathyanarayanan <knsathya@...nel.org>,
        x86@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 6/7] x86/kvm: Use bounce buffers for TD guest

On 6/9/21 4:55 PM, Kuppuswamy Sathyanarayanan wrote:
> From: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
> diff --git a/arch/x86/mm/mem_encrypt_common.c b/arch/x86/mm/mem_encrypt_common.c
> index 8053b43298ff..2da70f58b208 100644
> --- a/arch/x86/mm/mem_encrypt_common.c
> +++ b/arch/x86/mm/mem_encrypt_common.c
> @@ -9,6 +9,7 @@
>  
>  #include <asm/mem_encrypt_common.h>
>  #include <linux/dma-mapping.h>
> +#include <linux/swiotlb.h>
>  
>  /* Override for DMA direct allocation check - ARCH_HAS_FORCE_DMA_UNENCRYPTED */
>  bool force_dma_unencrypted(struct device *dev)
> @@ -21,3 +22,18 @@ bool force_dma_unencrypted(struct device *dev)
>  
>  	return false;
>  }
> +
> +/* Architecture __weak replacement functions */
> +void __init mem_encrypt_init(void)
> +{
> +	/*
> +	 * For TDX guest or SEV/SME, call into SWIOTLB to update
> +	 * the SWIOTLB DMA buffers
> +	 */
> +	if (sme_me_mask || prot_guest_has(PR_GUEST_MEM_ENCRYPT))
> +		swiotlb_update_mem_attributes();
> +
> +	if (sme_me_mask)
> +		amd_mem_encrypt_init();

The sme_me_mask is checked in amd_mem_encrypt_init(), so you should just
invoke amd_mem_encrypt_init() unconditionally.

Thanks,
Tom

> +}
> +
>