[PATCH -next] Documentation/hw-vuln: Update spectre doc

[Lin Yujun]

commit 7c693f54c873691 ("x86/speculation: Add spectre_v2=ibrs
option to support Kernel IBRS") adds the "ibrs " option  in
Documentation/admin-guide/kernel-parameters.txt but omits it to
Documentation/admin-guide/hw-vuln/spectre.rst, add it.

Signed-off-by: Lin Yujun <linyujun809@xxxxxxxxxx>
---
 Documentation/admin-guide/hw-vuln/spectre.rst | 1 +
 1 file changed, 1 insertion(+)

diff --git a/Documentation/admin-guide/hw-vuln/spectre.rst b/Documentation/admin-guide/hw-vuln/spectre.rst
index 2ce2a38cdd55..c4dcdb3d0d45 100644
--- a/Documentation/admin-guide/hw-vuln/spectre.rst
+++ b/Documentation/admin-guide/hw-vuln/spectre.rst
@@ -613,6 +613,7 @@ kernel command line.
                 eibrs                   enhanced IBRS
                 eibrs,retpoline         enhanced IBRS + Retpolines
                 eibrs,lfence            enhanced IBRS + LFENCE
+                ibrs                    use IBRS to protect kernel
 
 		Not specifying this option is equivalent to
 		spectre_v2=auto.
-- 
2.17.1