On 04/25/2014 01:29 PM, James Hogan wrote:
Hi David,

On Friday 25 April 2014 09:44:17 David Daney wrote:
On 04/25/2014 08:19 AM, James Hogan wrote:
Contrary to the comment, the guest CP0_EPC register cannot be set via
kvm_regs, since it is distinct from the guest PC. Add the EPC register
to the KVM_{GET,SET}_ONE_REG ioctl interface.

Signed-off-by: James Hogan <[email protected]>
Cc: Paolo Bonzini <[email protected]>
Cc: Gleb Natapov <[email protected]>
Cc: [email protected]
Cc: Ralf Baechle <[email protected]>
Cc: [email protected]
Cc: David Daney <[email protected]>
Cc: Sanjay Lal <[email protected]>

NACK...

---

   arch/mips/kvm/kvm_mips.c | 9 ++++++++-
   1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/arch/mips/kvm/kvm_mips.c b/arch/mips/kvm/kvm_mips.c
index 46cea0bad518..db41876cbac5 100644
--- a/arch/mips/kvm/kvm_mips.c
+++ b/arch/mips/kvm/kvm_mips.c
@@ -512,6 +512,7 @@ kvm_arch_vcpu_ioctl_set_mpstate(struct kvm_vcpu *vcpu,

   #define KVM_REG_MIPS_CP0_COMPARE     MIPS_CP0_32(11, 0)
   #define KVM_REG_MIPS_CP0_STATUS              MIPS_CP0_32(12, 0)
   #define KVM_REG_MIPS_CP0_CAUSE               MIPS_CP0_32(13, 0)

+#define KVM_REG_MIPS_CP0_EPC           MIPS_CP0_64(14, 0)

This is already called KVM_REG_MIPS_PC, you cannot change that.

KVM_REG_MIPS_PC gets you vcpu->arch.pc, i.e. the next address of guest
execution.

KVM_REG_MIPS_CP0_EPC gets you the guest's CP0 EPC register which is the PC of
the last guest exception.

They are quite distinct state, even though vcpu->arch.pc is read from the
*root context*'s CP0 EPC register after an exception or interrupt.


Sorry, my mistake.  I was confusing Root/Host and Guest state.

I remove my objection.

David Daney


Cheers
James


   #define KVM_REG_MIPS_CP0_EBASE               MIPS_CP0_32(15, 1)
   #define KVM_REG_MIPS_CP0_CONFIG              MIPS_CP0_32(16, 0)
   #define KVM_REG_MIPS_CP0_CONFIG1     MIPS_CP0_32(16, 1)

@@ -567,7 +568,7 @@ static u64 kvm_mips_get_one_regs[] = {

        KVM_REG_MIPS_CP0_ENTRYHI,
        KVM_REG_MIPS_CP0_STATUS,
        KVM_REG_MIPS_CP0_CAUSE,

-       /* EPC set via kvm_regs, et al. */
+       KVM_REG_MIPS_CP0_EPC,

        KVM_REG_MIPS_CP0_CONFIG,
        KVM_REG_MIPS_CP0_CONFIG1,
        KVM_REG_MIPS_CP0_CONFIG2,

@@ -620,6 +621,9 @@ static int kvm_mips_get_reg(struct kvm_vcpu *vcpu,

        case KVM_REG_MIPS_CP0_CAUSE:
                v = (long)kvm_read_c0_guest_cause(cop0);
                break;

+       case KVM_REG_MIPS_CP0_EPC:
+               v = (long)kvm_read_c0_guest_epc(cop0);
+               break;

        case KVM_REG_MIPS_CP0_ERROREPC:
                v = (long)kvm_read_c0_guest_errorepc(cop0);
                break;

@@ -716,6 +720,9 @@ static int kvm_mips_set_reg(struct kvm_vcpu *vcpu,

        case KVM_REG_MIPS_CP0_CAUSE:
                kvm_write_c0_guest_cause(cop0, v);
                break;

+       case KVM_REG_MIPS_CP0_EPC:
+               kvm_write_c0_guest_epc(cop0, v);
+               break;

        case KVM_REG_MIPS_CP0_ERROREPC:
                kvm_write_c0_guest_errorepc(cop0, v);
                break;

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