[PATCH 02/12] x86/ioapic: Gate decrypted mapping on cc_platform_has() attribute
From: Michael Kelley <hidden>
Date: 2022-10-20 17:58:35
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 IOAPIC 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 IOAPIC. In such a case, the IOAPIC must be accessed as private (encrypted). Fix this by gating the IOAPIC decrypted mapping on a new cc_platform_has() attribute that a subsequent patch in the series will set only for Hyper-V guests. The new attribute is named somewhat generically because similar paravisor emulation cases may arise in the future. Signed-off-by: Michael Kelley <redacted> --- arch/x86/kernel/apic/io_apic.c | 3 ++- include/linux/cc_platform.h | 13 +++++++++++++ 2 files changed, 15 insertions(+), 1 deletion(-)
diff --git a/arch/x86/kernel/apic/io_apic.c b/arch/x86/kernel/apic/io_apic.c
index a868b76..d2c1bf7 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_HAS_PARAVISOR)) + 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..b6c4a79 100644
--- a/include/linux/cc_platform.h
+++ b/include/linux/cc_platform.h@@ -90,6 +90,19 @@ enum cc_attr { * Examples include TDX Guest. */ CC_ATTR_HOTPLUG_DISABLED, + + /** + * @CC_ATTR_HAS_PARAVISOR: Guest VM is running with a paravisor + * + * The platform/OS is running as a guest/virtual machine with + * a paravisor in VMPL0. Having a paravisor affects things + * like whether the I/O APIC is emulated and operates in the + * encrypted or decrypted portion of the guest physical address + * space. + * + * Examples include Hyper-V SEV-SNP guests using vTOM. + */ + CC_ATTR_HAS_PARAVISOR, }; #ifdef CONFIG_ARCH_HAS_CC_PLATFORM
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1.8.3.1