[xen stable-4.15] SUPPORT.md: Document speculative attacks status of non-shim 32-bit PV

[patchbot@xxxxxxx]

commit 280d472f4fca070a10377e318d90cabfc2540810
Author:     Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
AuthorDate: Tue Mar 9 15:00:47 2021 +0000
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Tue May 4 14:58:03 2021 +0200

    SUPPORT.md: Document speculative attacks status of non-shim 32-bit PV
    
    This documents, but does not fix, XSA-370.
    
    Reported-by: Jann Horn <jannh@xxxxxxxxxx>
    Signed-off-by: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
    Signed-off-by: George Dunlap <george.dunlap@xxxxxxxxxx>
    Acked-by: Jan Beulich <jbeulich@xxxxxxxx>
---
 SUPPORT.md | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/SUPPORT.md b/SUPPORT.md
index d89af5abc8..9024d8a056 100644
--- a/SUPPORT.md
+++ b/SUPPORT.md
@@ -84,7 +84,16 @@ Traditional Xen PV guest
 
 No hardware requirements
 
-    Status: Supported
+    Status, x86_64: Supported
+    Status, x86_32, shim: Supported
+    Status, x86_32, without shim: Supported, with caveats
+
+Due to architectural limitations,
+32-bit PV guests must be assumed to be able to read arbitrary host memory
+using speculative execution attacks.
+Advisories will continue to be issued
+for new vulnerabilities related to un-shimmed 32-bit PV guests
+enabling denial-of-service attacks or privilege escalation attacks.
 
 ### x86/HVM
 
--
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