Re: [PATCH v2 1/6] arm64/hyperv: Support DeviceTree

[Roman Kisel]

On 5/15/2024 3:02 PM, Elliot Berman wrote:

On Tue, May 14, 2024 at 03:43:48PM -0700, Roman Kisel wrote:

The Virtual Trust Level platforms rely on DeviceTree, and the
arm64/hyperv code supports ACPI only. Update the logic to
support DeviceTree on boot as well as ACPI.

Could you use Call UID query from SMCCC? KVM [1] and Gunyah [2] have
been using this to identify if guest is running under those respective
hypervisors. This works in both DT and ACPI cases.

[1]: https://lore.kernel.org/all/20210330145430.996981-2-...@kernel.org/
[2]: https://lore.kernel.org/all/20240222-gunyah-v17-4-1e9da6763...@quicinc.com/

That would be very neat indeed, thanks! Talking to the hypervisor folks.

Signed-off-by: Roman Kisel <rom...@linux.microsoft.com>
---
  arch/arm64/hyperv/mshyperv.c | 34 +++++++++++++++++++++++++++++-----
  1 file changed, 29 insertions(+), 5 deletions(-)

diff --git a/arch/arm64/hyperv/mshyperv.c b/arch/arm64/hyperv/mshyperv.c
index b1a4de4eee29..208a3bcb9686 100644
--- a/arch/arm64/hyperv/mshyperv.c
+++ b/arch/arm64/hyperv/mshyperv.c
@@ -15,6 +15,9 @@
  #include <linux/errno.h>
  #include <linux/version.h>
  #include <linux/cpuhotplug.h>
+#include <linux/libfdt.h>
+#include <linux/of.h>
+#include <linux/of_fdt.h>
  #include <asm/mshyperv.h>

static bool hyperv_initialized;

@@ -27,6 +30,29 @@ int hv_get_hypervisor_version(union 
hv_hypervisor_version_info *info)
        return 0;
  }

+static bool hyperv_detect_fdt(void)

+{
+#ifdef CONFIG_OF
+       const unsigned long hyp_node = of_get_flat_dt_subnode_by_name(
+                       of_get_flat_dt_root(), "hypervisor");
+
+       return (hyp_node != -FDT_ERR_NOTFOUND) &&
+                       of_flat_dt_is_compatible(hyp_node, "microsoft,hyperv");
+#else
+       return false;
+#endif
+}
+
+static bool hyperv_detect_acpi(void)
+{
+#ifdef CONFIG_ACPI
+       return !acpi_disabled &&
+                       !strncmp((char *)&acpi_gbl_FADT.hypervisor_id, 
"MsHyperV", 8);
+#else
+       return false;
+#endif
+}
+
  static int __init hyperv_init(void)
  {
        struct hv_get_vp_registers_output       result;
@@ -35,13 +61,11 @@ static int __init hyperv_init(void)

/*

         * Allow for a kernel built with CONFIG_HYPERV to be running in
-        * a non-Hyper-V environment, including on DT instead of ACPI.
+        * a non-Hyper-V environment.
+        *
         * In such cases, do nothing and return success.
         */
-       if (acpi_disabled)
-               return 0;
-
-       if (strncmp((char *)&acpi_gbl_FADT.hypervisor_id, "MsHyperV", 8))
+       if (!hyperv_detect_fdt() && !hyperv_detect_acpi())
                return 0;

/* Setup the guest ID */

--
2.45.0


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--
Thank you,
Roman