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Re: [Xen-devel] [PATCH v2 4/6] xen/arm: make vpidr per vcpu

Hi Stefano,

On 19/02/18 21:58, Stefano Stabellini wrote:
On big.LITTLE systems not all cores have the same midr. Instead of
storing only one vpidr per domain, make it per vcpu and initialize it to
the value of the midr of the pcpu where the vcpu will run.

This way, assuming that the vcpu has been created with the right pcpu
affinity, the guest will be able to read the right vpidr value, matching
the one of the physical cpu.

Signed-off-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>


- remove warning message
- make vpidr per vcpu
  xen/arch/arm/domain.c        | 6 ++----
  xen/arch/arm/vcpreg.c        | 4 ++--
  xen/include/asm-arm/domain.h | 6 +++---
  3 files changed, 7 insertions(+), 9 deletions(-)

diff --git a/xen/arch/arm/domain.c b/xen/arch/arm/domain.c
index fb51415..41d5d25 100644
--- a/xen/arch/arm/domain.c
+++ b/xen/arch/arm/domain.c
@@ -180,7 +180,7 @@ static void ctxt_switch_to(struct vcpu *n)
p2m_restore_state(n); - WRITE_SYSREG32(n->domain->arch.vpidr, VPIDR_EL2);
+    WRITE_SYSREG32(n->arch.vpidr, VPIDR_EL2);

Do we really need to store the vpidr in struct vcpu? It would be simpler and more efficient (no memory access) to use directly read MDIR_EL1 and copy it to VPIDR_EL1.


Julien Grall

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