From: Oliver Kurth <okurth@vmware.com>
Date: Mon, 17 Jun 2019 18:41:35 +0000 (-0700)
Subject: Common header file change not applicable to open-vm-tools.
X-Git-Tag: stable-11.0.0~53
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=3583ad84072c618064dfea742faa763b5f8207f0;p=thirdparty%2Fopen-vm-tools.git

Common header file change not applicable to open-vm-tools.
---

diff --git a/open-vm-tools/lib/include/backdoor_def.h b/open-vm-tools/lib/include/backdoor_def.h
index 080b79439..9855267fb 100644
--- a/open-vm-tools/lib/include/backdoor_def.h
+++ b/open-vm-tools/lib/include/backdoor_def.h
@@ -447,8 +447,23 @@ Backdoor_CmdRequiresValidSegments(unsigned cmd)
  *
  * 3) Perform the x86 I/O space instruction.
  *
- * The vCPU executes the BKPT (32-bit code) or BRK (64-bit code) instruction
- * with the immediate X86_IO_BRK_IMM. Note that T32 code requires an 8-bit
+ * Several mechanisms are available:
+ *
+ * o From EL1
+ * The vCPU executes the HVC (64-bit code) instruction with the immediate
+ * X86_IO_MAGIC. This is the mechanism to favor from EL1 because it is
+ * architectural.
+ *
+ * o From EL1 and EL0
+ * 64-bit code: The vCPU sets X7<63:32> to X86_IO_MAGIC and executes the
+ *              MRS XZR, MDCCSR_EL0 instruction.
+ * 32-bit code: To be defined...
+ * This is the mechanism to favor from EL0 because it has a negligible impact
+ * on vCPU performance.
+ *
+ * o From EL1 and EL0
+ * The vCPU executes the BRK (64-bit code) or BKPT (32-bit code) instruction
+ * with the immediate X86_IO_MAGIC. Note that T32 code requires an 8-bit
  * immediate.
  *
  * 4) Read from general-purpose registers specific to the x86 I/O space
@@ -464,7 +479,7 @@ Backdoor_CmdRequiresValidSegments(unsigned cmd)
  *   byte access) or W0<15:0> (2 bytes access) or W0 (4 bytes access).
  */
 
-#define X86_IO_BRK_IMM        0x86
+#define X86_IO_MAGIC          0x86
 
 #define X86_IO_W7_SIZE_SHIFT  0
 #define X86_IO_W7_SIZE_MASK   (0x3 << X86_IO_W7_SIZE_SHIFT)