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[v4,09/10] x86/hyperv/vtl: Mark the wakeup mailbox page as private

Message ID 20250603-rneri-wakeup-mailbox-v4-9-d533272b7232@linux.intel.com
State New
Headers show
Series [v4,01/10] x86/acpi: Add a helper functions to setup and access the wakeup mailbox | expand

Commit Message

Ricardo Neri June 4, 2025, 12:15 a.m. UTC 
From: Yunhong Jiang <yunhong.jiang@linux.intel.com>

The current code maps MMIO devices as shared (decrypted) by default in a
confidential computing VM.

In a TDX environment, secondary CPUs are booted using the Multiprocessor
Wakeup Structure defined in the ACPI specification. The virtual firmware
and the operating system function in the guest context, without
intervention from the VMM. Map the physical memory of the mailbox as
private. Use the is_private_mmio() callback.

Reviewed-by: Michael Kelley <mhklinux@outlook.com>
Signed-off-by: Yunhong Jiang <yunhong.jiang@linux.intel.com>
Signed-off-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
---
Changes since v3:
 - Updated to use the renamed function acpi_get_mp_wakeup_mailbox_paddr().
 - Added Reviewed-by tag from Michael. Thanks!

Changes since v2:
 - Use the new helper function get_mp_wakeup_mailbox_paddr().
 - Edited the commit message for clarity.

Changes since v1:
 - Added the helper function within_page() to improve readability
 - Override the is_private_mmio() callback when detecting a TDX
   environment. The address of the mailbox is checked in
   hv_is_private_mmio_tdx().
---
 arch/x86/hyperv/hv_vtl.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)
diff mbox series

Patch

diff --git a/arch/x86/hyperv/hv_vtl.c b/arch/x86/hyperv/hv_vtl.c
index 8b497c8292d3..995d1de7a9be 100644
--- a/arch/x86/hyperv/hv_vtl.c
+++ b/arch/x86/hyperv/hv_vtl.c
@@ -54,6 +54,18 @@  static void  __noreturn hv_vtl_restart(char __maybe_unused *cmd)
 	hv_vtl_emergency_restart();
 }
 
+static inline bool within_page(u64 addr, u64 start)
+{
+	return addr >= start && addr < (start + PAGE_SIZE);
+}
+
+static bool hv_vtl_is_private_mmio_tdx(u64 addr)
+{
+	u64 mb_addr = acpi_get_mp_wakeup_mailbox_paddr();
+
+	return mb_addr && within_page(addr, mb_addr);
+}
+
 void __init hv_vtl_init_platform(void)
 {
 	pr_info("Linux runs in Hyper-V Virtual Trust Level\n");
@@ -61,6 +73,8 @@  void __init hv_vtl_init_platform(void)
 	/* There is no paravisor present if we are here. */
 	if (hv_isolation_type_tdx()) {
 		x86_init.resources.realmode_limit = SZ_4G;
+		x86_platform.hyper.is_private_mmio = hv_vtl_is_private_mmio_tdx;
+
 	} else {
 		x86_platform.realmode_reserve = x86_init_noop;
 		x86_platform.realmode_init = x86_init_noop;