On 2/19/2025 3:13 PM, Michael Kelley wrote:
From: Roman Kisel <romank@xxxxxxxxxxxxxxxxxxx> Sent: Tuesday, February 11, 2025 5:43 PM
[...]
}
+static bool hyperv_detect_via_acpi(void)
+{
+ if (acpi_disabled)
+ return false;
+#if IS_ENABLED(CONFIG_ACPI)
+ /* Hypervisor ID is only available in ACPI v6+. */
The comment is correct, but to me doesn't tell the full story.
I initially wondered why the revision test < 6 was being done,
since Hyper-V for ARM64 always provides ACPI 6.x or greater.
But the test is needed to catch running in some unknown
non-Hyper-V environment that has ACPI 5.x or less. In such a
case, it can't be Hyper-V, so just return false instead of testing
a bogus hypervisor_id field. Maybe a comment would help
explain it to someone like me who was confused. :-)
Thanks, I'll extend the comment to tell the whole story!
[...]
+ ms_hyperv.vtl = get_vtl();
The above statement looks like it will fail to compile on
arm64 since the get_vtl() function is entirely on the x86
side until Patch 3 of this series. As of this Patch 1, there's
no declaration of get_vtl() available to arm64.
I used my working branch for testing
https://github.com/romank-msft/linux-hyperv/tree/vtl_mode_arm64_v4
and didn't move that code around when chunking into patches.
Will fix the workflow, thanks for catching this!
+ /* Report if non-default VTL */
+ if (ms_hyperv.vtl > 0)
+ pr_info("Linux runs in Hyper-V Virtual Trust Level\n");
Could this message include the VTL number as well? In the long
run, I think there will be code at non-zero VTLs other than VTL 2.
Absolutely, will add!
+
ms_hyperv_late_init();
hyperv_initialized = true;
diff --git a/arch/arm64/include/asm/mshyperv.h
b/arch/arm64/include/asm/mshyperv.h
index 2e2f83bafcfb..a6d7eb9e167b 100644
--- a/arch/arm64/include/asm/mshyperv.h
+++ b/arch/arm64/include/asm/mshyperv.h
@@ -50,4 +50,9 @@ static inline u64 hv_get_msr(unsigned int reg)
#include <asm-generic/mshyperv.h>
+#define ARM_SMCCC_VENDOR_HYP_UID_HYPERV_REG_0 0x4d32ba58U
+#define ARM_SMCCC_VENDOR_HYP_UID_HYPERV_REG_1 0xcd244764U
+#define ARM_SMCCC_VENDOR_HYP_UID_HYPERV_REG_2 0x8eef6c75U
+#define ARM_SMCCC_VENDOR_HYP_UID_HYPERV_REG_3 0x16597024U
+
#endif
--
2.43.0
--
Thank you,
Roman
