linux-kernel - [PATCH v2 5/9] x86/hyperv: Mark ACPI wakeup mailbox page as private

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Message-Id: <20240823232327.2408869-6-yunhong.jiang@linux.intel.com>
Date: Fri, 23 Aug 2024 16:23:23 -0700
From: Yunhong Jiang <yunhong.jiang@...ux.intel.com>
To: tglx@...utronix.de,
	mingo@...hat.com,
	bp@...en8.de,
	dave.hansen@...ux.intel.com,
	x86@...nel.org,
	hpa@...or.com,
	robh@...nel.org,
	krzk+dt@...nel.org,
	conor+dt@...nel.org,
	kys@...rosoft.com,
	haiyangz@...rosoft.com,
	wei.liu@...nel.org,
	decui@...rosoft.com,
	rafael@...nel.org,
	lenb@...nel.org,
	kirill.shutemov@...ux.intel.com,
	yunhong.jiang@...ux.intel.com
Cc: linux-kernel@...r.kernel.org,
	devicetree@...r.kernel.org,
	linux-hyperv@...r.kernel.org,
	linux-acpi@...r.kernel.org
Subject: [PATCH v2 5/9] x86/hyperv: Mark ACPI wakeup mailbox page as private

Current code maps MMIO devices as shared (decrypted) by default in a
confidential computing VM. However, the wakeup mailbox must be accessed
as private (encrypted) because it's accessed by the OS and the firmware,
both are in the guest's context and encrypted. Set the wakeup mailbox
range as private explicitly.

Signed-off-by: Yunhong Jiang <yunhong.jiang@...ux.intel.com>
---
 arch/x86/hyperv/hv_vtl.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/arch/x86/hyperv/hv_vtl.c b/arch/x86/hyperv/hv_vtl.c
index 04775346369c..987a6a1200b0 100644
--- a/arch/x86/hyperv/hv_vtl.c
+++ b/arch/x86/hyperv/hv_vtl.c
@@ -22,10 +22,26 @@ static bool __init hv_vtl_msi_ext_dest_id(void)
 	return true;
 }
 
+static inline bool within_page(u64 addr, u64 start)
+{
+	return addr >= start && addr < (start + PAGE_SIZE);
+}
+
+/*
+ * The ACPI wakeup mailbox are accessed by the OS and the BIOS, both are in the
+ * guest's context, instead of the hypervisor/VMM context.
+ */
+static bool hv_is_private_mmio_tdx(u64 addr)
+{
+	return wakeup_mailbox_addr && within_page(addr, wakeup_mailbox_addr);
+}
+
 void __init hv_vtl_init_platform(void)
 {
 	pr_info("Linux runs in Hyper-V Virtual Trust Level\n");
 
+	if (hv_isolation_type_tdx())
+		x86_platform.hyper.is_private_mmio = hv_is_private_mmio_tdx;
 	x86_platform.realmode_reserve = x86_init_noop;
 	x86_platform.realmode_init = x86_init_noop;
 	x86_init.irqs.pre_vector_init = x86_init_noop;
-- 
2.25.1