[PATCH] xen/arm: Document the erratum #853709 related to Cortex A72

[Michal Orzel <michal.orzel@xxxxxxx>]

Workaround for Cortex-A57 erratum #852523 is already
in Xen but Cortex-A72 erratum #853709 is not although
it applies to the same issue.

Signed-off-by: Michal Orzel <michal.orzel@xxxxxxx>
---
 docs/misc/arm/silicon-errata.txt | 1 +
 xen/arch/arm/domain.c            | 6 ++++--
 2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/docs/misc/arm/silicon-errata.txt b/docs/misc/arm/silicon-errata.txt
index e15d0923e9..1f18a9df58 100644
--- a/docs/misc/arm/silicon-errata.txt
+++ b/docs/misc/arm/silicon-errata.txt
@@ -50,6 +50,7 @@ stable hypervisors.
 | ARM            | Cortex-A57      | #834220         | ARM64_ERRATUM_834220    
|
 | ARM            | Cortex-A57      | #1319537        | N/A                     
|
 | ARM            | Cortex-A72      | #1319367        | N/A                     
|
+| ARM            | Cortex-A72      | #853709         | N/A                     
|
 | ARM            | Cortex-A76      | #1165522        | N/A                     
|
 | ARM            | Neoverse-N1     | #1165522        | N/A
 | ARM            | MMU-500         | #842869         | N/A                     
|
diff --git a/xen/arch/arm/domain.c b/xen/arch/arm/domain.c
index 3b37f899b9..18cafcdda7 100644
--- a/xen/arch/arm/domain.c
+++ b/xen/arch/arm/domain.c
@@ -216,7 +216,8 @@ static void ctxt_switch_to(struct vcpu *n)
     WRITE_SYSREG64(n->arch.ttbr1, TTBR1_EL1);
 
     /*
-     * Erratum #852523: DACR32_EL2 must be restored before one of the
+     * Erratum #852523 (Cortex-A57) or erratum #853709 (Cortex-A72):
+     * DACR32_EL2 must be restored before one of the
      * following sysregs: SCTLR_EL1, TCR_EL1, TTBR0_EL1, TTBR1_EL1 or
      * CONTEXTIDR_EL1.
      */
@@ -245,7 +246,8 @@ static void ctxt_switch_to(struct vcpu *n)
 
     /*
      * This write to sysreg CONTEXTIDR_EL1 ensures we don't hit erratum
-     * #852523. I.e DACR32_EL2 is not correctly synchronized.
+     * #852523 (Cortex-A57) or #853709 (Cortex-A72).
+     * I.e DACR32_EL2 is not correctly synchronized.
      */
     WRITE_SYSREG(n->arch.contextidr, CONTEXTIDR_EL1);
     WRITE_SYSREG(n->arch.tpidr_el0, TPIDR_EL0);
-- 
2.28.0