linux-kernel - Re: [PATCH v8 2/2] x86/tdx: Support vmalloc() for tdx_enc_status

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Date:   Tue, 20 Jun 2023 11:34:17 -0700
From:   Sathyanarayanan Kuppuswamy 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>
To:     Dexuan Cui <decui@...rosoft.com>, ak@...ux.intel.com,
        arnd@...db.de, bp@...en8.de, brijesh.singh@....com,
        dan.j.williams@...el.com, dave.hansen@...el.com,
        dave.hansen@...ux.intel.com, haiyangz@...rosoft.com, hpa@...or.com,
        jane.chu@...cle.com, kirill.shutemov@...ux.intel.com,
        kys@...rosoft.com, linux-arch@...r.kernel.org,
        linux-hyperv@...r.kernel.org, luto@...nel.org, mingo@...hat.com,
        peterz@...radead.org, rostedt@...dmis.org, seanjc@...gle.com,
        tglx@...utronix.de, tony.luck@...el.com, wei.liu@...nel.org,
        x86@...nel.org, mikelley@...rosoft.com
Cc:     linux-kernel@...r.kernel.org, Tianyu.Lan@...rosoft.com,
        rick.p.edgecombe@...el.com
Subject: Re: [PATCH v8 2/2] x86/tdx: Support vmalloc() for
 tdx_enc_status_changed()

Hi,

On 6/20/23 8:48 AM, Dexuan Cui wrote:
> When a TDX guest runs on Hyper-V, the hv_netvsc driver's netvsc_init_buf()
> allocates buffers using vzalloc(), and needs to share the buffers with the
> host OS by calling set_memory_decrypted(), which is not working for
> vmalloc() yet. Add the support by handling the pages one by one.
> 
> Co-developed-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
> Reviewed-by: Michael Kelley <mikelley@...rosoft.com>
> Signed-off-by: Dexuan Cui <decui@...rosoft.com>
> ---

Looks good to me.

Reviewed-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com>

>  arch/x86/coco/tdx/tdx.c | 35 +++++++++++++++++++++++++++++------
>  1 file changed, 29 insertions(+), 6 deletions(-)
> 
> Changes in v2:
>   Changed tdx_enc_status_changed() in place.
> 
> Changes in v3:
>   No change since v2.
> 
> Changes in v4:
>   Added Kirill's Co-developed-by since Kirill helped to improve the
>     code by adding tdx_enc_status_changed_phys().
> 
>   Thanks Kirill for the clarification on load_unaligned_zeropad()!
> 
> Changes in v5:
>   Added Kirill's Signed-off-by.
>   Added Michael's Reviewed-by.
> 
> Changes in v6: None.
> 
> Changes in v7: None.
>   Note: there was a race between set_memory_encrypted() and
>   load_unaligned_zeropad(), which has been fixed by the 3 patches of
>   Kirill in the x86/tdx branch of the tip tree.
> 
> Changes in v8:
>   Rebased to tip.git's master branch.
> 
> diff --git a/arch/x86/coco/tdx/tdx.c b/arch/x86/coco/tdx/tdx.c
> index 0c198ab73aa7..a313d5ab42f1 100644
> --- a/arch/x86/coco/tdx/tdx.c
> +++ b/arch/x86/coco/tdx/tdx.c
> @@ -8,6 +8,7 @@
>  #include <linux/export.h>
>  #include <linux/io.h>
> +#include <linux/mm.h>
>  #include <asm/coco.h>
>  #include <asm/tdx.h>
>  #include <asm/vmx.h>
>  #include <asm/insn.h>
> @@ -752,6 +753,19 @@ static bool tdx_map_gpa(phys_addr_t start, phys_addr_t end, bool enc)
>  	return false;
>  }
>  
> +static bool tdx_enc_status_changed_phys(phys_addr_t start, phys_addr_t end,
> +					bool enc)
> +{
> +	if (!tdx_map_gpa(start, end, enc))
> +		return false;
> +
> +	/* shared->private conversion requires memory to be accepted before use */
> +	if (enc)
> +		return tdx_accept_memory(start, end);
> +
> +	return true;
> +}
> +
>  /*
>   * Inform the VMM of the guest's intent for this physical page: shared with
>   * the VMM or private to the guest.  The VMM is expected to change its mapping
> @@ -759,15 +773,24 @@ static bool tdx_map_gpa(phys_addr_t start, phys_addr_t end, bool enc)
>   */
>  static bool tdx_enc_status_changed(unsigned long vaddr, int numpages, bool enc)
>  {
> -	phys_addr_t start = __pa(vaddr);
> -	phys_addr_t end   = __pa(vaddr + numpages * PAGE_SIZE);
> +	unsigned long start = vaddr;
> +	unsigned long end = start + numpages * PAGE_SIZE;
>  
> -	if (!tdx_map_gpa(start, end, enc))
> +	if (offset_in_page(start) != 0)
>  		return false;
>  
> -	/* shared->private conversion requires memory to be accepted before use */
> -	if (enc)
> -		return tdx_accept_memory(start, end);
> +	if (!is_vmalloc_addr((void *)start))
> +		return tdx_enc_status_changed_phys(__pa(start), __pa(end), enc);
> +
> +	while (start < end) {
> +		phys_addr_t start_pa = slow_virt_to_phys((void *)start);
> +		phys_addr_t end_pa = start_pa + PAGE_SIZE;
> +
> +		if (!tdx_enc_status_changed_phys(start_pa, end_pa, enc))
> +			return false;
> +
> +		start += PAGE_SIZE;
> +	}
>  
>  	return true;
>  }

-- 
Sathyanarayanan Kuppuswamy
Linux Kernel Developer