[Xen-devel] Request complete reversion of XSA-60 patches

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

Hello,

Following CID 1128574 (Data race condition writing to
vcpu->arch.hvm_vcpu.cache_mode), I took a closer look at the expected
semantics surrounding domain->arch.hvm_domain.is_in_uc_mode

Embarrassingly, none of the reviewer (myself included) noticed that the
new "hvm_shadow_handle_cd()" was actually the regular CR0.CD switching
code for AMD SVM, which is now hidden behind an optional hvm_funcs
pointer only implemented in VT-x.

The changeset 62652c00efa55fb45374bcc92f7d96fc411aebb2 has therefore
caused a complete functional regression in AMD wrt CR0.CD handling.

From my understanding after investigating, the new
"hvm_shadow_handle_cd()" function was actually common which needed doing
in all cases, otherwise HAP logdirty mode will break.  Therefore, this
change appears to have broken migration as well.

Furthermore, the series already missed correct cache flushing in certain
cases (e.g. writing the hypercall page).


I request that the series be reverted in it's entirety to minimise the
collateral damage until a full, complete and correct set of fixes can be
made.

~Andrew

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