diff options
Diffstat (limited to 'arch/x86/coco/tdx/tdx.c')
| -rw-r--r-- | arch/x86/coco/tdx/tdx.c | 121 |
1 files changed, 112 insertions, 9 deletions
diff --git a/arch/x86/coco/tdx/tdx.c b/arch/x86/coco/tdx/tdx.c index c1cb90369915..078e2bac2553 100644 --- a/arch/x86/coco/tdx/tdx.c +++ b/arch/x86/coco/tdx/tdx.c @@ -7,6 +7,7 @@ #include <linux/cpufeature.h> #include <linux/export.h> #include <linux/io.h> +#include <linux/kexec.h> #include <asm/coco.h> #include <asm/tdx.h> #include <asm/vmx.h> @@ -14,6 +15,7 @@ #include <asm/insn.h> #include <asm/insn-eval.h> #include <asm/pgtable.h> +#include <asm/set_memory.h> /* MMIO direction */ #define EPT_READ 0 @@ -38,6 +40,8 @@ #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) { @@ -798,28 +802,124 @@ static bool tdx_enc_status_changed(unsigned long vaddr, int numpages, bool enc) return true; } -static bool tdx_enc_status_change_prepare(unsigned long vaddr, int numpages, - bool enc) +static int tdx_enc_status_change_prepare(unsigned long vaddr, int numpages, + bool enc) { /* * Only handle shared->private conversion here. * See the comment in tdx_early_init(). */ - if (enc) - return tdx_enc_status_changed(vaddr, numpages, enc); - return true; + if (enc && !tdx_enc_status_changed(vaddr, numpages, enc)) + return -EIO; + + return 0; } -static bool tdx_enc_status_change_finish(unsigned long vaddr, int numpages, +static int tdx_enc_status_change_finish(unsigned long vaddr, int numpages, bool enc) { /* * Only handle private->shared conversion here. * See the comment in tdx_early_init(). */ - if (!enc) - return tdx_enc_status_changed(vaddr, numpages, enc); - return true; + 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; +} + +/* Stop new private<->shared conversions */ +static void tdx_kexec_begin(void) +{ + if (!IS_ENABLED(CONFIG_KEXEC_CORE)) + return; + + /* + * Crash kernel reaches here with interrupts disabled: can't wait for + * conversions to finish. + * + * If race happened, just report and proceed. + */ + if (!set_memory_enc_stop_conversion()) + pr_warn("Failed to stop shared<->private conversions\n"); +} + +/* Walk direct mapping and convert all shared memory back to private */ +static void tdx_kexec_finish(void) +{ + unsigned long addr, end; + long found = 0, shared; + + if (!IS_ENABLED(CONFIG_KEXEC_CORE)) + return; + + lockdep_assert_irqs_disabled(); + + addr = PAGE_OFFSET; + end = PAGE_OFFSET + get_max_mapped(); + + while (addr < end) { + unsigned long size; + unsigned int level; + pte_t *pte; + + pte = lookup_address(addr, &level); + size = page_level_size(level); + + if (pte && pte_decrypted(*pte)) { + int pages = size / PAGE_SIZE; + + /* + * Touching memory with shared bit set triggers implicit + * conversion to shared. + * + * Make sure nobody touches the shared range from + * now on. + */ + set_pte(pte, __pte(0)); + + /* + * Memory encryption state persists across kexec. + * If tdx_enc_status_changed() fails in the first + * kernel, it leaves memory in an unknown state. + * + * If that memory remains shared, accessing it in the + * *next* kernel through a private mapping will result + * in an unrecoverable guest shutdown. + * + * The kdump kernel boot is not impacted as it uses + * a pre-reserved memory range that is always private. + * However, gathering crash information could lead to + * a crash if it accesses unconverted memory through + * a private mapping which is possible when accessing + * that memory through /proc/vmcore, for example. + * + * In all cases, print error info in order to leave + * enough bread crumbs for debugging. + */ + if (!tdx_enc_status_changed(addr, pages, true)) { + pr_err("Failed to unshare range %#lx-%#lx\n", + addr, addr + size); + } + + found += pages; + } + + addr += size; + } + + __flush_tlb_all(); + + shared = atomic_long_read(&nr_shared); + if (shared != found) { + pr_err("shared page accounting is off\n"); + pr_err("nr_shared = %ld, nr_found = %ld\n", shared, found); + } } void __init tdx_early_init(void) @@ -881,6 +981,9 @@ void __init tdx_early_init(void) x86_platform.guest.enc_cache_flush_required = tdx_cache_flush_required; x86_platform.guest.enc_tlb_flush_required = tdx_tlb_flush_required; + x86_platform.guest.enc_kexec_begin = tdx_kexec_begin; + x86_platform.guest.enc_kexec_finish = tdx_kexec_finish; + /* * TDX intercepts the RDMSR to read the X2APIC ID in the parallel * bringup low level code. That raises #VE which cannot be handled |