[Xen-changelog] [xen master] xen/arm: Save HCR_EL2 when a guest took the SError

[patchbot@xxxxxxx]

commit 04ff92f4537f8f47ebd4eb95808619443979b2b9
Author:     Wei Chen <Wei.Chen@xxxxxxx>
AuthorDate: Wed Apr 5 17:09:07 2017 +0800
Commit:     Stefano Stabellini <sstabellini@xxxxxxxxxx>
CommitDate: Wed Apr 5 12:12:14 2017 -0700

    xen/arm: Save HCR_EL2 when a guest took the SError
    
    The HCR_EL2.VSE (HCR.VA for aarch32) bit can be used to generate a
    virtual abort to guest. The HCR_EL2.VSE bit has a peculiar feature
    of getting cleared when the guest has taken the abort (this is the
    only bit that behaves as such in HCR_EL2 register).
    
    This means that if we set the HCR_EL2.VSE bit to signal such an abort,
    we must preserve it in the guest context until it disappears from
    HCR_EL2, and at which point it must be cleared from the context. This
    is achieved by reading back from HCR_EL2 until the guest takes the
    fault.
    
    If we preserved a pending VSE in guest context, we have to restore
    it to HCR_EL2 when context switch to this guest. This is achieved
    by writing saved HCR_EL2 value in guest context back to HCR_EL2
    register before return to guest. This had been done by the patch
    of "Restore HCR_EL2 register".
    
    Signed-off-by: Wei Chen <Wei.Chen@xxxxxxx>
    Reviewed-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>
---
 xen/arch/arm/traps.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/xen/arch/arm/traps.c b/xen/arch/arm/traps.c
index ebe25c6..35ca0ed 100644
--- a/xen/arch/arm/traps.c
+++ b/xen/arch/arm/traps.c
@@ -2694,7 +2694,18 @@ static void do_trap_smc(struct cpu_user_regs *regs, 
const union hsr hsr)
 static void enter_hypervisor_head(struct cpu_user_regs *regs)
 {
     if ( guest_mode(regs) )
+    {
+        /*
+         * If we pended a virtual abort, preserve it until it gets cleared.
+         * See ARM ARM DDI 0487A.j D1.14.3 (Virtual Interrupts) for details,
+         * but the crucial bit is "On taking a vSError interrupt, HCR_EL2.VSE
+         * (alias of HCR.VA) is cleared to 0."
+         */
+        if ( current->arch.hcr_el2 & HCR_VA )
+            current->arch.hcr_el2 = READ_SYSREG(HCR_EL2);
+
         gic_clear_lrs(current);
+    }
 }
 
 asmlinkage void do_trap_hypervisor(struct cpu_user_regs *regs)
--
generated by git-patchbot for /home/xen/git/xen.git#master

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