Re: [Xen-devel] [PATCH] Don't clear HCR_VM bit when updating VTTBR.

[Jun Sun <jsun@xxxxxxxxxx>]

Sorry to be pushy - any feedback on this simple little patch?

Cheers.

Jun

On Mon, Oct 10, 2016 at 12:27 PM, Jun Sun <jsun@xxxxxxxxxx> wrote:

Currently function p2m_restore_state() would clear HCR_VM bit, i.e.,
disabling stage2 translation, before updating VTTBR register. After
some research and talking to ARM support, I got confirmed that this is not
necessary. We are currently working on a new platform that would need this
to be removed.

The patch is tested on FVP foundation model.

Signed-off-by: Jun Sun <jsun@xxxxxxxxxx>
---
 xen/arch/arm/p2m.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/xen/arch/arm/p2m.c b/xen/arch/arm/p2m.c
index cc5634b..e4991df 100644
--- a/xen/arch/arm/p2m.c
+++ b/xen/arch/arm/p2m.c
@@ -140,8 +140,6 @@ void p2m_restore_state(struct vcpu *n)
         return;

     hcr = READ_SYSREG(HCR_EL2);
-    WRITE_SYSREG(hcr & ~HCR_VM, HCR_EL2);
-    isb();

     WRITE_SYSREG64(p2m->vttbr, VTTBR_EL2);
     isb();
--
2.7.4

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