[PATCH v5 01/14] x86/ioapic: Gate decrypted mapping on cc_platform_has() attribute
From: Michael Kelley <hidden>
Date: 2023-01-12 21:49:43
Also in:
linux-arch, linux-hyperv, linux-iommu, linux-pci, lkml
Subsystem:
the rest, x86 architecture (32-bit and 64-bit) · Maintainers:
Linus Torvalds, Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen
Current code always maps the IO-APIC as shared (decrypted) in a confidential VM. But Hyper-V guest VMs on AMD SEV-SNP with vTOM enabled use a paravisor running in VMPL0 to emulate the IO-APIC. In such a case, the IO-APIC must be accessed as private (encrypted) because the paravisor emulates the IO-APIC at an address below vTOM, where all accesses are encrypted. Add a new CC attribute which determines how the IO-APIC MMIO mapping should be established depending on the platform the kernel is running on as a guest. Signed-off-by: Michael Kelley <redacted> Reviewed-by: Wei Liu <wei.liu@kernel.org> Reviewed-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com> --- arch/x86/kernel/apic/io_apic.c | 3 ++- include/linux/cc_platform.h | 12 ++++++++++++ 2 files changed, 14 insertions(+), 1 deletion(-)
diff --git a/arch/x86/kernel/apic/io_apic.c b/arch/x86/kernel/apic/io_apic.c
index a868b76..2b70e2e 100644
--- a/arch/x86/kernel/apic/io_apic.c
+++ b/arch/x86/kernel/apic/io_apic.c@@ -2686,7 +2686,8 @@ static void io_apic_set_fixmap(enum fixed_addresses idx, phys_addr_t phys) * Ensure fixmaps for IOAPIC MMIO respect memory encryption pgprot * bits, just like normal ioremap(): */ - flags = pgprot_decrypted(flags); + if (!cc_platform_has(CC_ATTR_ACCESS_IOAPIC_ENCRYPTED)) + flags = pgprot_decrypted(flags); __set_fixmap(idx, phys, flags); }
diff --git a/include/linux/cc_platform.h b/include/linux/cc_platform.h
index cb0d6cd..7b63a7d 100644
--- a/include/linux/cc_platform.h
+++ b/include/linux/cc_platform.h@@ -90,6 +90,18 @@ enum cc_attr { * Examples include TDX Guest. */ CC_ATTR_HOTPLUG_DISABLED, + + /** + * @CC_ATTR_ACCESS_IOAPIC_ENCRYPTED: Guest VM IO-APIC is encrypted + * + * The platform/OS is running as a guest/virtual machine with + * an IO-APIC that is emulated by a paravisor running in the + * guest VM context. As such, the IO-APIC is accessed in the + * encrypted portion of the guest physical address space. + * + * Examples include Hyper-V SEV-SNP guests using vTOM. + */ + CC_ATTR_ACCESS_IOAPIC_ENCRYPTED, }; #ifdef CONFIG_ARCH_HAS_CC_PLATFORM
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1.8.3.1