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

[patchbot@xxxxxxx]

commit f776e5fb3ee699745f6442ec8c47d0fa647e0575
Author:     Michal Orzel <michal.orzel@xxxxxxx>
AuthorDate: Wed Oct 14 12:05:41 2020 +0200
Commit:     Julien Grall <jgrall@xxxxxxxxxx>
CommitDate: Wed Oct 14 18:02:50 2020 +0100

    xen/arm: Document the erratum #853709 related to Cortex A72
    
    The Cortex-A72 erratum #853709 is the same as the Cortex-A57
    erratum #852523. As the latter is already workaround, we only
    need to update the documentation.
    
    Signed-off-by: Michal Orzel <michal.orzel@xxxxxxx>
    [julieng: Reworded the commit message]
    Reviewed-by: Julien Grall <jgrall@xxxxxxxxxx>
    Reviewed-by: Bertrand Marquis <bertrand.marquis@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);
--
generated by git-patchbot for /home/xen/git/xen.git#staging