Re: [PATCH] Add support for ESRT loading under Xen

[Jan Beulich <jbeulich@xxxxxxxx>]

On 25.08.2022 23:52, Demi Marie Obenour wrote:
> @@ -40,6 +41,38 @@
>  
>  #define efi_data(op) (op.u.efi_runtime_call)
>  
> +static_assert(XEN_PAGE_SHIFT == EFI_PAGE_SHIFT,
> +              "Mismatch between EFI_PAGE_SHIFT and XEN_PAGE_SHIFT");
> +
> +bool xen_efi_mem_desc_lookup(u64 phys_addr, efi_memory_desc_t *md)
> +{
> +     struct xen_platform_op op = {
> +             .cmd = XENPF_firmware_info,
> +             .u.firmware_info = {
> +                     .type = XEN_FW_EFI_INFO,
> +                     .index = XEN_FW_EFI_MEM_INFO,
> +                     .u.efi_info.mem.addr = phys_addr,
> +                     .u.efi_info.mem.size = ((u64)-1ULL) - phys_addr,
> +             }
> +     };
> +     union xenpf_efi_info *info = &op.u.firmware_info.u.efi_info;
> +     int rc;
> +
> +     memset(md, 0, sizeof(*md)); /* initialize md even on failure */
> +     rc = HYPERVISOR_platform_op(&op);
> +     if (rc) {
> +             pr_warn("Could not obtain information on address %llu from Xen: 
> "
> +                     "error %d\n", phys_addr, rc);
> +             return false;
> +     }
> +
> +     md->attribute = info->mem.attr;
> +     md->type = info->mem.type;
> +     md->num_pages = info->mem.size >> XEN_PAGE_SHIFT;
> +     md->phys_addr = info->mem.addr;

As indicated in reply to your patch changing XEN_FW_EFI_MEM_INFO in
the hypervisor: While this may fit the ESRT purpose, the address you
return here is not necessarily the start of the region, and hence
this function is not a general Xen replacement for the non-Xen
function. Therefore I think it also shouldn't give the impression of
doing so.

Jan