@@ -2510,9 +2510,18 @@ END_FTR_SECTION_IFSET(CPU_FTR_ARCH_207S)
clrrdi r4, r4, 3
std r4, VCPU_DAWR(r3)
std r5, VCPU_DAWRX(r3)
+ /*
+ * If came in through the real mode hcall handler then it is necessary
+ * to write the registers since the return path won't. Otherwise it is
+ * sufficient to store then in the vcpu struct as they will be loaded
+ * next time the vcpu is run.
+ */
+ mfmsr r6
+ andi. r6, r6, MSR_DR /* in real mode? */
+ bne 4f
mtspr SPRN_DAWR, r4
mtspr SPRN_DAWRX, r5
- li r3, 0
+4: li r3, 0
blr
_GLOBAL(kvmppc_h_cede) /* r3 = vcpu pointer, r11 = msr, r13 = paca */
The hcall H_SET_DAWR is used by a guest to set the data address watchpoint register (DAWR). This hcall is handled in the host in kvmppc_h_set_dawr() which can be called in either real mode on the guest exit path from hcall_try_real_mode() in book3s_hv_rmhandlers.S, or in virtual mode when called from kvmppc_pseries_do_hcall() in book3s_hv.c. The function kvmppc_h_set_dawr updates the dawr and dawrx fields in the vcpu struct accordingly and then also writes the respective values into the DAWR and DAWRX registers directly. It is necessary to write the registers directly here when calling the function in real mode since the path to re-enter the guest won't do this. However when in virtual mode the host DAWR and DAWRX values have already been restored, and so writing the registers would overwrite these. Additionally there is no reason to write the guest values here as these will be read from the vcpu struct and written to the registers appropriately the next time the vcpu is run. This also avoids the case when handling h_set_dawr for a nested guest where the guest hypervisor isn't able to write the DAWR and DAWRX registers directly and must rely on the real hypervisor to do this for it when it calls H_ENTER_NESTED. Signed-off-by: Suraj Jitindar Singh <sjitindarsingh@gmail.com> --- arch/powerpc/kvm/book3s_hv_rmhandlers.S | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-)