From: Yunhong Jiang <[email protected]> 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. Signed-off-by: Yunhong Jiang <[email protected]> Signed-off-by: Ricardo Neri <[email protected]> --- Changes in v8: - Included linux/acpi.h to add missing definitions that caused build breaks (kernel test robot) Changes in v7: - Dropped check for !CONFIG_X86_MAILBOX_WAKEUP. The symbol is no longer valid and now we have a stub for !CONFIG_ACPI. - Dropped Reviewed-by tags from Dexuan and Michael as this patch changed. Changes in v6: - Fixed a compile error with !CONFIG_X86_MAILBOX_WAKEUP. - Added Reviewed-by tag from Dexuan. Thanks! Changes in v5: - None Changes in v4: - Updated to use the renamed function acpi_get_mp_wakeup_mailbox_paddr(). - Added Reviewed-by tag from Michael. Thanks! Changes in v3: - Use the new helper function get_mp_wakeup_mailbox_paddr(). - Edited the commit message for clarity. Changes in v2: - 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 | 17 +++++++++++++++++ 1 file changed, 17 insertions(+) diff --git a/arch/x86/hyperv/hv_vtl.c b/arch/x86/hyperv/hv_vtl.c index 752101544663..2af825f7a447 100644 --- a/arch/x86/hyperv/hv_vtl.c +++ b/arch/x86/hyperv/hv_vtl.c @@ -6,6 +6,9 @@ * Saurabh Sengar <[email protected]> */ +#include <linux/acpi.h> + +#include <asm/acpi.h> #include <asm/apic.h> #include <asm/boot.h> #include <asm/desc.h> @@ -59,6 +62,18 @@ 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) { /* @@ -71,6 +86,8 @@ 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; -- 2.43.0
