On Fri, May 14, 2021 at 03:14:41PM +0000, Michael Kelley wrote:

From: Mark Rutland <mark.rutland@arm.com> Sent: Friday, May 14, 2021 5:53 AM

quoted

On Wed, May 12, 2021 at 10:37:42AM -0700, Michael Kelley wrote:

quoted

hyperv-tlfs.h defines Hyper-V interfaces from the Hyper-V Top Level
Functional Spec (TLFS), and #includes the architecture-independent
part of hyperv-tlfs.h in include/asm-generic.  The published TLFS
is distinctly oriented to x86/x64, so the ARM64-specific
hyperv-tlfs.h includes information for ARM64 that is not yet formally
published. The TLFS is available here:

  docs.microsoft.com/en-us/virtualization/hyper-v-on-windows/reference/tlfs

mshyperv.h defines Linux-specific structures and routines for
interacting with Hyper-V on ARM64, and #includes the architecture-
independent part of mshyperv.h in include/asm-generic.

Use these definitions to provide utility functions to make
Hyper-V hypercalls and to get and set Hyper-V provided
registers associated with a virtual processor.

Signed-off-by: Michael Kelley <redacted>
Reviewed-by: Sunil Muthuswamy <redacted>
---
 MAINTAINERS                          |   3 +
 arch/arm64/Kbuild                    |   1 +
 arch/arm64/hyperv/Makefile           |   2 +
 arch/arm64/hyperv/hv_core.c          | 130 +++++++++++++++++++++++++++++++++++
 arch/arm64/include/asm/hyperv-tlfs.h |  69 +++++++++++++++++++
 arch/arm64/include/asm/mshyperv.h    |  54 +++++++++++++++
 6 files changed, 259 insertions(+)
 create mode 100644 arch/arm64/hyperv/Makefile
 create mode 100644 arch/arm64/hyperv/hv_core.c
 create mode 100644 arch/arm64/include/asm/hyperv-tlfs.h
 create mode 100644 arch/arm64/include/asm/mshyperv.h

quoted

+/*
+ * hv_do_hypercall- Invoke the specified hypercall
+ */
+u64 hv_do_hypercall(u64 control, void *input, void *output)
+{
+	struct arm_smccc_res	res;
+	u64			input_address;
+	u64			output_address;
+
+	input_address = input ? virt_to_phys(input) : 0;
+	output_address = output ? virt_to_phys(output) : 0;

I may have asked this before, but are `input` and `output` always linear
map pointers, or can they ever be vmalloc pointers?

Otherwise, this looks fine to me.

The caller must ensure that hypercall arguments are aligned to
4 Kbytes, and no larger than 4 Kbytes, since that's the page size
used by Hyper-V regardless of the guest page size.  A per-CPU
4 Kbyte memory area (hyperv_pcpu_input_arg) meeting these
requirements is pre-allocated that callers can use for this purpose.

What I was trying to find out was how that was allocated, as vmalloc()'d
pointers aren't legitimate to pass to virt_to_phys().

From scanning ahead to patch 5, I see that memory comes from kmalloc(),
and so it is legitimate to use virt_to_phys().


I see; and from patch 5 I see that memory come from kmalloc(), and will
therefore be part of the linear map, and so virt_to_phys() is
legitimate.

What I was asking here was how that memory was allocated. So long as
those are the only buffers used, this looks fine to me.

Thanks,
Mark.