Re: [PATCH v4 1/3] x86/sgx: Repurpose the owner field as the virtual address of virtual EPC page

[Kai Huang <kai.huang@intel.com>]

On Wed, 2022-06-08 at 11:26 +0800, Zhiquan Li wrote:
> When a page triggers a machine check, it only reports the
> physical address of EPC page. But in order to inject #MC into
> hypervisor, the virtual address is required. Then repurpose the
> "owner" field as the virtual address of the virtual EPC page so that
> arch_memory_failure() can easily retrieve it.
> 
> Add a new EPC page flag - SGX_EPC_PAGE_KVM_GUEST to interpret the
> meaning of the field.
> 
> Signed-off-by: Zhiquan Li <zhiquan1.li@intel.com>
> ---
> Changes since V3:
> - Move the definition of EPC page flag SGX_EPC_PAGE_KVM_GUEST from
>   Cathy's third patch of SGX rebootless recovery patch set but discard
>   irrelevant portion, since it might need more time to re-forge and
>   these are two different features.
>   Link: https://lore.kernel.org/linux-sgx/41704e5d4c03b49fcda12e695595211d950cfb08.camel@kernel.org/T/#m9782d23496cacecb7da07a67daa79f4b322ae170
> 
> Changes since V2:
> - Rework the patch suggested by Jarkko.
> - Remove struct sgx_vepc_page and relevant code.
> - Remove new EPC page flag SGX_EPC_PAGE_IS_VEPC definition as it is
>   duplicated to SGX_EPC_PAGE_KVM_GUEST.
>   Link: https://lore.kernel.org/linux-sgx/eb95b32ecf3d44a695610cf7f2816785@intel.com/T/#u
> 
> Changes since V1:
> - Add documentation suggested by Jarkko.
> ---
>  arch/x86/kernel/cpu/sgx/sgx.h  | 2 ++
>  arch/x86/kernel/cpu/sgx/virt.c | 4 +++-
>  2 files changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kernel/cpu/sgx/sgx.h b/arch/x86/kernel/cpu/sgx/sgx.h
> index 0f17def9fe6f..b43582da1bcf 100644
> --- a/arch/x86/kernel/cpu/sgx/sgx.h
> +++ b/arch/x86/kernel/cpu/sgx/sgx.h
> @@ -28,6 +28,8 @@
>  
>  /* Pages on free list */
>  #define SGX_EPC_PAGE_IS_FREE		BIT(1)
> +/* Pages allocated for KVM guest */
> +#define SGX_EPC_PAGE_KVM_GUEST		BIT(2)
>  
>  struct sgx_epc_page {
>  	unsigned int section;
> diff --git a/arch/x86/kernel/cpu/sgx/virt.c b/arch/x86/kernel/cpu/sgx/virt.c
> index 6a77a14eee38..776ae5c1c032 100644
> --- a/arch/x86/kernel/cpu/sgx/virt.c
> +++ b/arch/x86/kernel/cpu/sgx/virt.c
> @@ -46,10 +46,12 @@ static int __sgx_vepc_fault(struct sgx_vepc *vepc,
>  	if (epc_page)
>  		return 0;
>  
> -	epc_page = sgx_alloc_epc_page(vepc, false);
> +	epc_page = sgx_alloc_epc_page((void *)addr, false);
>  	if (IS_ERR(epc_page))
>  		return PTR_ERR(epc_page);
>  
> +	epc_page->flags |= SGX_EPC_PAGE_KVM_GUEST;
> +
>  	ret = xa_err(xa_store(&vepc->page_array, index, epc_page, GFP_KERNEL));
>  	if (ret)
>  		goto err_free;


Acked-by: Kai Huang <kai.huang@intel.com>

-- 
Thanks,
-Kai