On 3/25/24 3:39 AM, Kirill A. Shutemov wrote:
> The kernel will convert all shared memory back to private during kexec.
> The direct mapping page tables will provide information on which memory
> is shared.
>
> It is extremely important to convert all shared memory. If a page is
> missed, it will cause the second kernel to crash when it accesses it.
>
> Keep track of the number of shared pages. This will allow for
> cross-checking against the shared information in the direct mapping and
> reporting if the shared bit is lost.
>
> Signed-off-by: Kirill A. Shutemov <kirill.shute...@linux.intel.com>
> ---
Looks good to me.
Reviewed-by: Kuppuswamy Sathyanarayanan
<sathyanarayanan.kuppusw...@linux.intel.com>
> arch/x86/coco/tdx/tdx.c | 7 +++++++
> 1 file changed, 7 insertions(+)
>
> diff --git a/arch/x86/coco/tdx/tdx.c b/arch/x86/coco/tdx/tdx.c
> index 26fa47db5782..979891e97d83 100644
> --- a/arch/x86/coco/tdx/tdx.c
> +++ b/arch/x86/coco/tdx/tdx.c
> @@ -38,6 +38,8 @@
>
> #define TDREPORT_SUBTYPE_0 0
>
> +static atomic_long_t nr_shared;
> +
> /* Called from __tdx_hypercall() for unrecoverable failure */
> noinstr void __noreturn __tdx_hypercall_failed(void)
> {
> @@ -821,6 +823,11 @@ static int tdx_enc_status_change_finish(unsigned long
> vaddr, int numpages,
> if (!enc && !tdx_enc_status_changed(vaddr, numpages, enc))
> return -EIO;
>
> + if (enc)
> + atomic_long_sub(numpages, &nr_shared);
> + else
> + atomic_long_add(numpages, &nr_shared);
> +
> return 0;
> }
>
--
Sathyanarayanan Kuppuswamy
Linux Kernel Developer
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