On 07/24/2012 05:43 PM, Alexander Graf wrote:
On 07/24/2012 10:53 AM, Raghavendra K T wrote:
From: Raghavendra K T <raghavendra.kt@xxxxxxxxxxxxxxxxxx>
Thanks Alex for KVM_HC_FEATURES inputs and Jan for VAPIC_POLL_IRQ,
and Peter (HPA) for suggesting hypercall ABI addition.
Signed-off-by: Raghavendra K T <raghavendra.kt@xxxxxxxxxxxxxxxxxx>
---
Please have a closer look at Hypercall ABI newly added
Changes since last post:
- Added hypercall ABI (Peter)
- made KVM_HC_VAPIC_POLL_IRQ active explicitly (Randy)
TODO: We need to add history details of each hypercall as suggested by
HPA,
which I could not trace easily. Hope it is easy for hypercall authors
Documentation/virtual/hypercalls.txt | 71
++++++++++++++++++++++++++++++++++
1 files changed, 71 insertions(+), 0 deletions(-)
create mode 100644 Documentation/virtual/hypercalls.txt
diff --git a/Documentation/virtual/hypercalls.txt
b/Documentation/virtual/hypercalls.txt
new file mode 100644
index 0000000..caffc08
--- /dev/null
+++ b/Documentation/virtual/hypercalls.txt
@@ -0,0 +1,71 @@
+Hypercall ABI:
+=============
+A brief look at calling conventions of X86, S390 and PPC
+X86:
+ KVM Hypercalls have a three-byte sequence of either the vmrun or the
vmmrun
+ instruction. The hypervisor can replace it with instructions that are
+ guaranteed to be supported.
+
+ Up to four arguments may be passed in rbx, rcx, rdx, and rsi
respectively.
+ The hypercall number should be placed in rax and the return value
will be
+ placed in rax. No other registers will be clobbered unless
explicitly stated
+ by the particular hypercall.
+
+S390:
+ R2-R7 are used for parameters 1-6. In addition, R1 is used for
hypercall
+ number. The return value is written to R2.
+
+ S390 uses diagnose instruction as hypercall (0x500) along with
hypercall
+ number in R1.
+
+ PoewerPC:
PowerPC
Sorry for the typo.
+ It uses R3-R10 and hypercall number in R11. R4-R11 are used as
output registers.
+ Return value is placed in R3.
+
+ KVM hypercalls uses 4 byte opcode, that are patched with
'hypercall-instructions'
+ property inside the device tree's /hypervisor node.
+ For more information refer to Documentation/virtual/kvm/ppc-pv.txt
What exactly is this document supposed to cover? We have 3 different
hypercall ABIs in KVM on PowerPC:
Thanks for the detailed information on PPC hypercalls.
My intention was to cover KVM specific hypercalls here.
Patch is wrongly generated against Documentation/virtual/ instead of
Documentation/virtual/kvm will correct that.
Information you have provided should be very useful in understanding
PPC hypercalls. Do you wish to have (2), (3) below goto some doc?
1) KVM hypercalls (ePAPR)
The ePAPR compliant hypercall implementation. This one is used for KVM
specific hypercalls. All hypercalls get a KVM vendor prefix (42) and
then the hypercall id. We also implement generic hypercalls here, like
the ePAPR idle hcall. The instruction sequence for these is listed in
the device tree, as you noted above. It's available on all targets.
2) PAPR hypercalls
To run server PowerPC PAPR guests (-M pseries in QEMU), we need to
handle PAPR hypercalls. These are the same hypercalls that pHyp, the
POWER hypervisor implements. Some of them are handled in the kernel,
some are handled in user space. This is only available on book3s_64.
3) OSI hypercalls
In parallel to QEMU, there is another user of KVM on PowerPC:
Mac-on-Linux. That project had its own hypercalls long before we came
along with KVM, so to maintain compatibility we also support their
hypercalls. All of these get forwarded to user space. This is only
useful on book3s_32, but can be used with book3s_64 as well.
+
+KVM Hypercalls Documentation
+===========================
+The template for each hypercall is:
+1. Hypercall name, value.
+2. Architecture(s)
+3. Status (deprecated, obsolete, active)
+4. Purpose
+
+1. KVM_HC_VAPIC_POLL_IRQ
+------------------------
+Value: 1
What are the value fields supposed to mean?
Value field is just #define value of the hypercall in header.
If that does not make much sense probably it can be dropped.
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