Re: [PATCH v1 3/8] x86/psp: Register PSP platform device when ASP table is present
From: Tom Lendacky
Date: Wed Feb 01 2023 - 09:57:47 EST
On 2/1/23 08:09, Jeremi Piotrowski wrote:
On Tue, Jan 31, 2023 at 12:49:54PM -0600, Tom Lendacky wrote:
On 1/23/23 09:22, Jeremi Piotrowski wrote:
The ASP table contains the memory location of the register window for
communication with the Platform Security Processor. The device is not
exposed as an acpi node, so it is necessary to probe for the table and
register a platform_device to represent it in the kernel.
At least conceptually, the same PSP may be exposed on the PCIe bus as
well, in which case it would be necessary to choose whether to use a PCI
BAR or the register window defined in ASPT for communication. There is
no advantage to using the ACPI and there are no known bare-metal systems
that expose the ASP table, so device registration is restricted to the
only systems known to provide an ASPT: Hyper-V VMs. Hyper-V VMs also do
not expose the PSP over PCIe.
This is a skeleton device at this point, as the ccp driver is not yet
prepared to correctly probe it. Interrupt configuration will come later
on as well.
Signed-off-by: Jeremi Piotrowski <jpiotrowski@xxxxxxxxxxxxxxxxxxx>
---
arch/x86/kernel/Makefile | 2 +-
arch/x86/kernel/psp.c | 39 +++++++++++++++++++++++++++++++++++++++
Based on comments about other SEV related items, this should
probably be moved into the arch/x86/coco/sev/ directory.
Thanks,
Tom
I'll do that. This will make the code depend on CONFIG_ARCH_HAS_CC_PLATFORM
and CONFIG_AMD_MEM_ENCRYPT, the latter selects the former. This will work
as long as CONFIG_AMD_MEM_ENCRYPT continues to be needed for both SNP guest
and host sides.
CONFIG_AMD_MEM_ENCRYPT is only required on the guest side. It is not
needed to launch an SEV guest of any type. I believe the latest SNP
hypervisor patches are being updated to remove that dependency and replace
it with CONFIG_KVM_AMD_SEV. So you'll have to figure out what you want for
your CONFIG requirement.
Thanks,
Tom
Jeremi
2 files changed, 40 insertions(+), 1 deletion(-)
create mode 100644 arch/x86/kernel/psp.c
diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
index f901658d9f7c..e2e19f2d08a7 100644
--- a/arch/x86/kernel/Makefile
+++ b/arch/x86/kernel/Makefile
@@ -139,7 +139,7 @@ obj-$(CONFIG_UNWINDER_ORC) += unwind_orc.o
obj-$(CONFIG_UNWINDER_FRAME_POINTER) += unwind_frame.o
obj-$(CONFIG_UNWINDER_GUESS) += unwind_guess.o
-obj-$(CONFIG_AMD_MEM_ENCRYPT) += sev.o
+obj-$(CONFIG_AMD_MEM_ENCRYPT) += psp.o sev.o
obj-$(CONFIG_CFI_CLANG) += cfi.o
diff --git a/arch/x86/kernel/psp.c b/arch/x86/kernel/psp.c
new file mode 100644
index 000000000000..d404df47cc04
--- /dev/null
+++ b/arch/x86/kernel/psp.c
@@ -0,0 +1,39 @@
+// SPDX-License-Identifier: GPL-2.0-only
+
+#include <linux/platform_data/psp.h>
+#include <linux/platform_device.h>
+#include <asm/hypervisor.h>
+
+static struct platform_device psp_device = {
+ .name = "psp",
+ .id = PLATFORM_DEVID_NONE,
+};
+
+static int __init psp_init_platform_device(void)
+{
+ struct psp_platform_data pdata = {};
+ struct resource res[1];
+ int err;
+
+ /*
+ * The ACPI PSP interface is mutually exclusive with the PCIe interface,
+ * but there is no reason to use the ACPI interface over the PCIe one.
+ * Restrict probing ACPI PSP to platforms known to only expose the ACPI
+ * interface, which at this time is SNP-host capable Hyper-V VMs.
+ */
+ if (!hypervisor_is_type(X86_HYPER_MS_HYPERV))
+ return -ENODEV;
+
+ err = acpi_parse_aspt(res, &pdata);
+ if (err)
+ return err;
+ err = platform_device_add_resources(&psp_device, res, 1);
+ if (err)
+ return err;
+
+ err = platform_device_register(&psp_device);
+ if (err)
+ return err;
+ return 0;
+}
+device_initcall(psp_init_platform_device);