From f4c9361f97c40d365c34f9cb8b8bc3eae0ee7778 Mon Sep 17 00:00:00 2001 From: Isaku Yamahata Date: Wed, 6 Apr 2022 02:29:37 +0300 Subject: [PATCH] x86/tdx/ioapic: Add shared bit for IOAPIC base address The kernel interacts with each bare-metal IOAPIC with a special MMIO page. When running under KVM, the guest's IOAPICs are emulated by KVM. When running as a TDX guest, the guest needs to mark each IOAPIC mapping as "shared" with the host. This ensures that TDX private protections are not applied to the page, which allows the TDX host emulation to work. ioremap()-created mappings such as virtio will be marked as shared by default. However, the IOAPIC code does not use ioremap() and instead uses the fixmap mechanism. Introduce a special fixmap helper just for the IOAPIC code. Ensure that it marks IOAPIC pages as "shared". This replaces set_fixmap_nocache() with __set_fixmap() since __set_fixmap() allows custom 'prot' values. AMD SEV gets IOAPIC pages shared because FIXMAP_PAGE_NOCACHE has _ENC bit clear. TDX has to set bit to share the page with the host. Signed-off-by: Isaku Yamahata Signed-off-by: Kuppuswamy Sathyanarayanan Signed-off-by: Kirill A. Shutemov Signed-off-by: Dave Hansen Reviewed-by: Andi Kleen Reviewed-by: Tony Luck Reviewed-by: Dave Hansen Reviewed-by: Thomas Gleixner Link: https://lkml.kernel.org/r/20220405232939.73860-29-kirill.shutemov@linux.intel.com --- arch/x86/kernel/apic/io_apic.c | 18 ++++++++++++++++-- 1 file changed, 16 insertions(+), 2 deletions(-) diff --git a/arch/x86/kernel/apic/io_apic.c b/arch/x86/kernel/apic/io_apic.c index c1bb384935b05..a868b76cd3d42 100644 --- a/arch/x86/kernel/apic/io_apic.c +++ b/arch/x86/kernel/apic/io_apic.c @@ -65,6 +65,7 @@ #include #include #include +#include #define for_each_ioapic(idx) \ for ((idx) = 0; (idx) < nr_ioapics; (idx)++) @@ -2677,6 +2678,19 @@ static struct resource * __init ioapic_setup_resources(void) return res; } +static void io_apic_set_fixmap(enum fixed_addresses idx, phys_addr_t phys) +{ + pgprot_t flags = FIXMAP_PAGE_NOCACHE; + + /* + * Ensure fixmaps for IOAPIC MMIO respect memory encryption pgprot + * bits, just like normal ioremap(): + */ + flags = pgprot_decrypted(flags); + + __set_fixmap(idx, phys, flags); +} + void __init io_apic_init_mappings(void) { unsigned long ioapic_phys, idx = FIX_IO_APIC_BASE_0; @@ -2709,7 +2723,7 @@ fake_ioapic_page: __func__, PAGE_SIZE, PAGE_SIZE); ioapic_phys = __pa(ioapic_phys); } - set_fixmap_nocache(idx, ioapic_phys); + io_apic_set_fixmap(idx, ioapic_phys); apic_printk(APIC_VERBOSE, "mapped IOAPIC to %08lx (%08lx)\n", __fix_to_virt(idx) + (ioapic_phys & ~PAGE_MASK), ioapic_phys); @@ -2838,7 +2852,7 @@ int mp_register_ioapic(int id, u32 address, u32 gsi_base, ioapics[idx].mp_config.flags = MPC_APIC_USABLE; ioapics[idx].mp_config.apicaddr = address; - set_fixmap_nocache(FIX_IO_APIC_BASE_0 + idx, address); + io_apic_set_fixmap(FIX_IO_APIC_BASE_0 + idx, address); if (bad_ioapic_register(idx)) { clear_fixmap(FIX_IO_APIC_BASE_0 + idx); return -ENODEV; -- 2.30.2