From: Demi Marie Obenour Date: Thu, 19 Jan 2023 19:03:57 +0000 (-0500) Subject: efi: xen: Implement memory descriptor lookup based on hypercall X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=aca1d27ac38a61d7db4b56418386992cb96b63f0;p=linux.git efi: xen: Implement memory descriptor lookup based on hypercall Xen on x86 boots dom0 in EFI mode but without providing a memory map. This means that some consistency checks we would like to perform on configuration tables or other data structures in memory are not currently possible. Xen does, however, expose EFI memory descriptor info via a Xen hypercall, so let's wire that up instead. It turns out that the returned information is not identical to what Linux's efi_mem_desc_lookup would return: the address returned is the address passed to the hypercall, and the size returned is the number of bytes remaining in the configuration table. However, none of the callers of efi_mem_desc_lookup() currently care about this. In the future, Xen may gain a hypercall that returns the actual start address, which can be used instead. Co-developed-by: Ard Biesheuvel Signed-off-by: Ard Biesheuvel Signed-off-by: Demi Marie Obenour Tested-by: Marek Marczykowski-Górecki Signed-off-by: Ard Biesheuvel --- diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c index d295be1160399..90142f6e588d6 100644 --- a/drivers/firmware/efi/efi.c +++ b/drivers/firmware/efi/efi.c @@ -478,7 +478,7 @@ void __init efi_find_mirror(void) * and if so, populate the supplied memory descriptor with the appropriate * data. */ -int efi_mem_desc_lookup(u64 phys_addr, efi_memory_desc_t *out_md) +int __efi_mem_desc_lookup(u64 phys_addr, efi_memory_desc_t *out_md) { efi_memory_desc_t *md; @@ -512,6 +512,9 @@ int efi_mem_desc_lookup(u64 phys_addr, efi_memory_desc_t *out_md) return -ENOENT; } +extern int efi_mem_desc_lookup(u64 phys_addr, efi_memory_desc_t *out_md) + __weak __alias(__efi_mem_desc_lookup); + /* * Calculate the highest address of an efi memory descriptor. */ diff --git a/drivers/xen/efi.c b/drivers/xen/efi.c index d1ff2186ebb48..3c792353b7308 100644 --- a/drivers/xen/efi.c +++ b/drivers/xen/efi.c @@ -26,6 +26,7 @@ #include #include +#include #include #include @@ -292,3 +293,38 @@ void __init xen_efi_runtime_setup(void) efi.get_next_high_mono_count = xen_efi_get_next_high_mono_count; efi.reset_system = xen_efi_reset_system; } + +int efi_mem_desc_lookup(u64 phys_addr, efi_memory_desc_t *out_md) +{ + static_assert(XEN_PAGE_SHIFT == EFI_PAGE_SHIFT, + "Mismatch between EFI_PAGE_SHIFT and XEN_PAGE_SHIFT"); + struct xen_platform_op op; + union xenpf_efi_info *info = &op.u.firmware_info.u.efi_info; + int rc; + + if (!efi_enabled(EFI_PARAVIRT) || efi_enabled(EFI_MEMMAP)) + return __efi_mem_desc_lookup(phys_addr, out_md); + phys_addr &= ~(u64)(EFI_PAGE_SIZE - 1); + op = (struct xen_platform_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_MAX - phys_addr, + }, + }; + + rc = HYPERVISOR_platform_op(&op); + if (rc) { + pr_warn("Failed to lookup header 0x%llx in Xen memory map: error %d\n", + phys_addr, rc); + } + + out_md->phys_addr = info->mem.addr; + out_md->num_pages = info->mem.size >> EFI_PAGE_SHIFT; + out_md->type = info->mem.type; + out_md->attribute = info->mem.attr; + + return 0; +} diff --git a/include/linux/efi.h b/include/linux/efi.h index f6b107da1cbc1..4d7a44f609900 100644 --- a/include/linux/efi.h +++ b/include/linux/efi.h @@ -731,6 +731,7 @@ extern u64 efi_mem_attribute (unsigned long phys_addr, unsigned long size); extern int __init efi_uart_console_only (void); extern u64 efi_mem_desc_end(efi_memory_desc_t *md); extern int efi_mem_desc_lookup(u64 phys_addr, efi_memory_desc_t *out_md); +extern int __efi_mem_desc_lookup(u64 phys_addr, efi_memory_desc_t *out_md); extern void efi_mem_reserve(phys_addr_t addr, u64 size); extern int efi_mem_reserve_persistent(phys_addr_t addr, u64 size); extern void efi_initialize_iomem_resources(struct resource *code_resource,