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Peter Anvin" , virtualization@lists.linux.dev, bcm-kernel-feedback-list@broadcom.com, linux-kernel@vger.kernel.org, Christoph Lameter , Andrew Morton , Bo Gan , linux-mm@kvack.org, linux-arch@vger.kernel.org, linux-coco@lists.linux.dev, kvm@vger.kernel.org, Jonathan Corbet , "K. Y. Srinivasan" , Haiyang Zhang , Long Li , Andy Lutomirski , Peter Zijlstra , linux-doc@vger.kernel.org, linux-hyperv@vger.kernel.org, Nathan Chancellor , Kees Cook , Ashish Kalra Subject: [PATCH v2 5/6] x86/tdx: Support early sharing of kernel data Date: Tue, 29 Sep 2026 00:02:54 -0400 Message-ID: <20260929040256.543767-6-zack.rusin@broadcom.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260929040256.543767-1-zack.rusin@broadcom.com> References: <20260929040256.543767-1-zack.rusin@broadcom.com> Precedence: bulk X-Mailing-List: linux-coco@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-DetectorID-Processed: b00c1d49-9d2e-4205-b15f-d015386d3d5e Share pages before the page allocator is available, after both their direct-map and kernel-image mappings have been made shared. Preserve initial contents in a private scratch page, matching the AMD early helper, and use the existing MapGPA path and shared-page accounting. UP per-CPU data has an image alias. Drop shared image mappings before kexec converts their backing pages to private through the direct map. Suggested-by: Kiryl Shutsemau Link: https://lore.kernel.org/r/aqqGUAX65s4LdJkr@thinkstation Signed-off-by: Zack Rusin --- arch/x86/coco/tdx/tdx.c | 32 ++++++++++++++++++++++++++++++++ 1 file changed, 32 insertions(+) diff --git a/arch/x86/coco/tdx/tdx.c b/arch/x86/coco/tdx/tdx.c index f904a636d449..4a683e9eafc3 100644 --- a/arch/x86/coco/tdx/tdx.c +++ b/arch/x86/coco/tdx/tdx.c @@ -4,6 +4,7 @@ #undef pr_fmt #define pr_fmt(fmt) "tdx: " fmt +#include #include #include #include @@ -18,6 +19,7 @@ #include #include +#include #include #include /* MMIO direction */ @@ -1006,6 +1008,23 @@ static int tdx_enc_status_change_finish(unsigned long vaddr, int numpages, return 0; } +static char tdx_early_buffer[PAGE_SIZE] __initdata __aligned(PAGE_SIZE); + +static int __init tdx_early_decrypt_page(unsigned long addr, unsigned long alias) +{ + void *buffer = __va(__pa_symbol(tdx_early_buffer)); + int ret; + + memcpy(buffer, (void *)addr, PAGE_SIZE); + clflush_cache_range((void *)addr, PAGE_SIZE); + early_set_page_decrypted(addr, alias); + ret = tdx_enc_status_change_finish(addr, 1, false); + if (ret) + return ret; + memcpy((void *)addr, buffer, PAGE_SIZE); + return 0; +} + /* Stop new private<->shared conversions */ static void tdx_kexec_begin(void) { @@ -1033,6 +1052,18 @@ static void tdx_kexec_finish(void) lockdep_assert_irqs_disabled(); + /* Drop image aliases before the direct-map walk makes pages private. */ + addr = (unsigned long)_text; + while (addr < _brk_end) { + unsigned int level; + pte_t *pte = lookup_address(addr, &level); + + if (pte && pte_decrypted(*pte)) + set_pte(pte, __pte(0)); + addr = (addr & page_level_mask(level)) + page_level_size(level); + } + __flush_tlb_all(); + addr = PAGE_OFFSET; end = PAGE_OFFSET + get_max_mapped(); @@ -1160,6 +1191,7 @@ void __init tdx_early_init(void) */ x86_platform.guest.enc_status_change_prepare = tdx_enc_status_change_prepare; x86_platform.guest.enc_status_change_finish = tdx_enc_status_change_finish; + x86_init.paging.early_decrypt_page = tdx_early_decrypt_page; x86_platform.guest.enc_cache_flush_required = tdx_cache_flush_required; x86_platform.guest.enc_tlb_flush_required = tdx_tlb_flush_required; -- 2.53.0