On Tue, Dec 06, 2022 at 04:33:20PM -0800, Dexuan Cui wrote:
> GHCI spec for TDX 1.0 says that the MapGPA call may fail with the R10
> error code = TDG.VP.VMCALL_RETRY (1), and the guest must retry this
> operation for the pages in the region starting at the GPA specified
> in R11.
>
> When a TDX guest runs on Hyper-V, Hyper-V returns the retry error
> when hyperv_init() -> swiotlb_update_mem_attributes() ->
> set_memory_decrypted() decrypts up to 1GB of swiotlb bounce buffers.
>
> Signed-off-by: Dexuan Cui <decui@xxxxxxxxxxxxx>
> ---
>
> Changes in v2:
> Used __tdx_hypercall() directly in tdx_map_gpa().
> Added a max_retry_cnt of 1000.
> Renamed a few variables, e.g., r11 -> map_fail_paddr.
>
> arch/x86/coco/tdx/tdx.c | 64 +++++++++++++++++++++++++++++++++--------
> 1 file changed, 52 insertions(+), 12 deletions(-)
>
> diff --git a/arch/x86/coco/tdx/tdx.c b/arch/x86/coco/tdx/tdx.c
> index 3fee96931ff5..cdeda698d308 100644
> --- a/arch/x86/coco/tdx/tdx.c
> +++ b/arch/x86/coco/tdx/tdx.c
> @@ -20,6 +20,8 @@
> /* TDX hypercall Leaf IDs */
> #define TDVMCALL_MAP_GPA 0x10001
>
> +#define TDVMCALL_STATUS_RETRY 1
> +
> /* MMIO direction */
> #define EPT_READ 0
> #define EPT_WRITE 1
> @@ -692,14 +694,15 @@ static bool try_accept_one(phys_addr_t *start, unsigned long len,
> }
>
> /*
> - * 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
> - * of the page in response.
> + * Notify the VMM about page mapping conversion. More info about ABI
> + * can be found in TDX Guest-Host-Communication Interface (GHCI),
> + * section "TDG.VP.VMCALL<MapGPA>".
> */
> -static bool tdx_enc_status_changed(unsigned long vaddr, int numpages, bool enc)
> +static bool tdx_map_gpa(phys_addr_t start, phys_addr_t end, bool enc)
> {
> - phys_addr_t start = __pa(vaddr);
> - phys_addr_t end = __pa(vaddr + numpages * PAGE_SIZE);
> + int max_retry_cnt = 1000, retry_cnt = 0;
Hm. max_retry_cnt looks too high to me. I expected to see 3 or something.
Any justification for it to be *that* high?
--
Kiryl Shutsemau / Kirill A. Shutemov
